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  • Firefox 18 Metro Preview Release now Available for Download

    - by Asian Angel
    With Windows 8 general release fast approaching Mozilla has delivered a new nightly build of Firefox for the operating system. This new build delivers awesome browser goodness for both the Modern UI (Metro) and Desktop modes. Image shown above courtesy of Mozilla Blog. This is what the Modern UI Tile will look like on the Start Screen. Image shown below courtesy of Brian R. Bondy. 7 Ways To Free Up Hard Disk Space On Windows HTG Explains: How System Restore Works in Windows HTG Explains: How Antivirus Software Works

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  • Download, Install, and Update Metro-Style Apps from the Windows Store in Windows 8

    - by Lori Kaufman
    The Windows Store is similar to the app stores for Apple iOS and Android devices and Windows phones. It allows you to buy and download both free and paid Metro-style apps for Windows 8. When you purchase an app from the Windows Store, it can be installed on up to five Windows PCs or tablets. A Microsoft email account is also required to download and install apps from the Windows store. NOTE: How-To Geek has released a Geek Trivia app for Windows 8. For more information about the app and for a link to download it, see our article. This article shows you how to download, install, and update Metro-style apps from the Windows Store. We also show you how to uninstall an app from the Metro Start screen. Why Enabling “Do Not Track” Doesn’t Stop You From Being Tracked HTG Explains: What is the Windows Page File and Should You Disable It? How To Get a Better Wireless Signal and Reduce Wireless Network Interference

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  • The problems with Avoiding Smurf Naming classes with namespaces

    - by Daniel Koverman
    I pulled the term smurf naming from here (number 21). To save anyone not familiar the trouble, Smurf naming is the act of prefixing a bunch of related classes, variables, etc with a common prefix so you end up with "a SmurfAccountView passes a SmurfAccountDTO to the SmurfAccountController", etc. The solution I've generally heard to this is to make a smurf namespace and drop the smurf prefixes. This has generally served me well, but I'm running into two problems. I'm working with a library with a Configuration class. It could have been called WartmongerConfiguration but it's in the Wartmonger namespace, so it's just called Configuration. I likewise have a Configuration class which could be called SmurfConfiguration, but it is in the Smurf namespace so that would be redundant. There are places in my code where Smurf.Configuration appears alongside Wartmonger.Configuration and typing out fully qualified names is clunky and makes the code less readable. It would be nicer to deal with a SmurfConfiguration and (if it was my code and not a library) WartmongerConfiguration. I have a class called Service in my Smurf namespace which could have been called SmurfService. Service is a facade on top of a complex Smurf library which runs Smurf jobs. SmurfService seems like a better name because Service without the Smurf prefix is so incredibly generic. I can accept that SmurfService was already a generic, useless name and taking away smurf merely made this more apparent. But it could have been named Runner, Launcher, etc and it would still "feel better" to me as SmurfLauncher because I don't know what a Launcher does, but I know what a SmurfLauncher does. You could argue that what a Smurf.Launcher does should be just as apparent as a Smurf.SmurfLauncher, but I could see `Smurf.Launcher being some kind of class related to setup rather than a class that launches smurfs. If there is an open and shut way to deal with either of these that would be great. If not, what are some common practices to mitigate their annoyance?

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  • Metro, Authentication, and the ASP.NET Web API

    - by Stephen.Walther
    Imagine that you want to create a Metro style app written with JavaScript and you want to communicate with a remote web service. For example, you are creating a movie app which retrieves a list of movies from a movies service. In this situation, how do you authenticate your Metro app and the Metro user so not just anyone can call the movies service? How can you identify the user making the request so you can return user specific data from the service? The Windows Live SDK supports a feature named Single Sign-On. When a user logs into a Windows 8 machine using their Live ID, you can authenticate the user’s identity automatically. Even better, when the Metro app performs a call to a remote web service, you can pass an authentication token to the remote service and prevent unauthorized access to the service. The documentation for Single Sign-On is located here: http://msdn.microsoft.com/en-us/library/live/hh826544.aspx In this blog entry, I describe the steps that you need to follow to use Single Sign-On with a (very) simple movie app. We build a Metro app which communicates with a web service created using the ASP.NET Web API. Creating the Visual Studio Solution Let’s start by creating a Visual Studio solution which contains two projects: a Windows Metro style Blank App project and an ASP.NET MVC 4 Web Application project. Name the Metro app MovieApp and the ASP.NET MVC application MovieApp.Services. When you create the ASP.NET MVC application, select the Web API template: After you create the two projects, your Visual Studio Solution Explorer window should look like this: Configuring the Live SDK You need to get your hands on the Live SDK and register your Metro app. You can download the latest version of the SDK (version 5.2) from the following address: http://www.microsoft.com/en-us/download/details.aspx?id=29938 After you download the Live SDK, you need to visit the following website to register your Metro app: https://manage.dev.live.com/build Don’t let the title of the website — Windows Push Notifications & Live Connect – confuse you, this is the right place. Follow the instructions at the website to register your Metro app. Don’t forget to follow the instructions in Step 3 for updating the information in your Metro app’s manifest. After you register, your client secret is displayed. Record this client secret because you will need it later (we use it with the web service): You need to configure one more thing. You must enter your Redirect Domain by visiting the following website: https://manage.dev.live.com/Applications/Index Click on your application name, click Edit Settings, click the API Settings tab, and enter a value for the Redirect Domain field. You can enter any domain that you please just as long as the domain has not already been taken: For the Redirect Domain, I entered http://superexpertmovieapp.com. Create the Metro MovieApp Next, we need to create the MovieApp. The MovieApp will: 1. Use Single Sign-On to log the current user into Live 2. Call the MoviesService web service 3. Display the results in a ListView control Because we use the Live SDK in the MovieApp, we need to add a reference to it. Right-click your References folder in the Solution Explorer window and add the reference: Here’s the HTML page for the Metro App: <!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <title>MovieApp</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.1.0.RC/css/ui-dark.css" rel="stylesheet" /> <script src="//Microsoft.WinJS.1.0.RC/js/base.js"></script> <script src="//Microsoft.WinJS.1.0.RC/js/ui.js"></script> <!-- Live SDK --> <script type="text/javascript" src="/LiveSDKHTML/js/wl.js"></script> <!-- WebServices references --> <link href="/css/default.css" rel="stylesheet" /> <script src="/js/default.js"></script> </head> <body> <div id="tmplMovie" data-win-control="WinJS.Binding.Template"> <div class="movieItem"> <span data-win-bind="innerText:title"></span> <br /><span data-win-bind="innerText:director"></span> </div> </div> <div id="lvMovies" data-win-control="WinJS.UI.ListView" data-win-options="{ itemTemplate: select('#tmplMovie') }"> </div> </body> </html> The HTML page above contains a Template and ListView control. These controls are used to display the movies when the movies are returned from the movies service. Notice that the page includes a reference to the Live script that we registered earlier: <!-- Live SDK --> <script type="text/javascript" src="/LiveSDKHTML/js/wl.js"></script> The JavaScript code looks like this: (function () { "use strict"; var REDIRECT_DOMAIN = "http://superexpertmovieapp.com"; var WEBSERVICE_URL = "http://localhost:49743/api/movies"; function init() { WinJS.UI.processAll().done(function () { // Get element and control references var lvMovies = document.getElementById("lvMovies").winControl; // Login to Windows Live var scopes = ["wl.signin"]; WL.init({ scope: scopes, redirect_uri: REDIRECT_DOMAIN }); WL.login().then( function(response) { // Get the authentication token var authenticationToken = response.session.authentication_token; // Call the web service var options = { url: WEBSERVICE_URL, headers: { authenticationToken: authenticationToken } }; WinJS.xhr(options).done( function (xhr) { var movies = JSON.parse(xhr.response); var listMovies = new WinJS.Binding.List(movies); lvMovies.itemDataSource = listMovies.dataSource; }, function (xhr) { console.log(xhr.statusText); } ); }, function(response) { throw WinJS.ErrorFromName("Failed to login!"); } ); }); } document.addEventListener("DOMContentLoaded", init); })(); There are two constants which you need to set to get the code above to work: REDIRECT_DOMAIN and WEBSERVICE_URL. The REDIRECT_DOMAIN is the domain that you entered when registering your app with Live. The WEBSERVICE_URL is the path to your web service. You can get the correct value for WEBSERVICE_URL by opening the Project Properties for the MovieApp.Services project, clicking the Web tab, and getting the correct URL. The port number is randomly generated. In my code, I used the URL  “http://localhost:49743/api/movies”. Assuming that the user is logged into Windows 8 with a Live account, when the user runs the MovieApp, the user is logged into Live automatically. The user is logged in with the following code: // Login to Windows Live var scopes = ["wl.signin"]; WL.init({ scope: scopes, redirect_uri: REDIRECT_DOMAIN }); WL.login().then(function(response) { // Do something }); The scopes setting determines what the user has permission to do. For example, access the user’s SkyDrive or access the user’s calendar or contacts. The available scopes are listed here: http://msdn.microsoft.com/en-us/library/live/hh243646.aspx In our case, we only need the wl.signin scope which enables Single Sign-On. After the user signs in, you can retrieve the user’s Live authentication token. The authentication token is passed to the movies service to authenticate the user. Creating the Movies Service The Movies Service is implemented as an API controller in an ASP.NET MVC 4 Web API project. Here’s what the MoviesController looks like: using System.Collections.Generic; using System.Linq; using System.Net; using System.Net.Http; using System.Web.Http; using JWTSample; using MovieApp.Services.Models; namespace MovieApp.Services.Controllers { public class MoviesController : ApiController { const string CLIENT_SECRET = "NtxjF2wu7JeY1unvVN-lb0hoeWOMUFoR"; // GET api/values public HttpResponseMessage Get() { // Authenticate // Get authenticationToken var authenticationToken = Request.Headers.GetValues("authenticationToken").FirstOrDefault(); if (authenticationToken == null) { return new HttpResponseMessage(HttpStatusCode.Unauthorized); } // Validate token var d = new Dictionary<int, string>(); d.Add(0, CLIENT_SECRET); try { var myJWT = new JsonWebToken(authenticationToken, d); } catch { return new HttpResponseMessage(HttpStatusCode.Unauthorized); } // Return results return Request.CreateResponse( HttpStatusCode.OK, new List<Movie> { new Movie {Title="Star Wars", Director="Lucas"}, new Movie {Title="King Kong", Director="Jackson"}, new Movie {Title="Memento", Director="Nolan"} } ); } } } Because the Metro app performs an HTTP GET request, the MovieController Get() action is invoked. This action returns a set of three movies when, and only when, the authentication token is validated. The Movie class looks like this: using Newtonsoft.Json; namespace MovieApp.Services.Models { public class Movie { [JsonProperty(PropertyName="title")] public string Title { get; set; } [JsonProperty(PropertyName="director")] public string Director { get; set; } } } Notice that the Movie class uses the JsonProperty attribute to change Title to title and Director to director to make JavaScript developers happy. The Get() method validates the authentication token before returning the movies to the Metro app. To get authentication to work, you need to provide the client secret which you created at the Live management site. If you forgot to write down the secret, you can get it again here: https://manage.dev.live.com/Applications/Index The client secret is assigned to a constant at the top of the MoviesController class. The MoviesController class uses a helper class named JsonWebToken to validate the authentication token. This class was created by the Windows Live team. You can get the source code for the JsonWebToken class from the following GitHub repository: https://github.com/liveservices/LiveSDK/blob/master/Samples/Asp.net/AuthenticationTokenSample/JsonWebToken.cs You need to add an additional reference to your MVC project to use the JsonWebToken class: System.Runtime.Serialization. You can use the JsonWebToken class to get a unique and validated user ID like this: var user = myJWT.Claims.UserId; If you need to store user specific information then you can use the UserId property to uniquely identify the user making the web service call. Running the MovieApp When you first run the Metro MovieApp, you get a screen which asks whether the app should have permission to use Single Sign-On. This screen never appears again after you give permission once. Actually, when I first ran the app, I get the following error: According to the error, the app is blocked because “We detected some suspicious activity with your Online Id account. To help protect you, we’ve temporarily blocked your account.” This appears to be a bug in the current preview release of the Live SDK and there is more information about this bug here: http://social.msdn.microsoft.com/Forums/en-US/messengerconnect/thread/866c495f-2127-429d-ab07-842ef84f16ae/ If you click continue, and continue running the app, the error message does not appear again.  Summary The goal of this blog entry was to describe how you can validate Metro apps and Metro users when performing a call to a remote web service. First, I explained how you can create a Metro app which takes advantage of Single Sign-On to authenticate the current user against Live automatically. You learned how to register your Metro app with Live and how to include an authentication token in an Ajax call. Next, I explained how you can validate the authentication token – retrieved from the request header – in a web service. I discussed how you can use the JsonWebToken class to validate the authentication token and retrieve the unique user ID.

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  • Saving user details on OnSuspending event for Metro Style Apps

    - by nmarun
    I recently started getting to know about Metro Style Apps on Windows 8. It looks pretty interesting so far and VS2011 definitely helps making it easier to learn and create Metro Style Apps. One of the features available for developers is the ability to save user data so it can be retrieved the next time the app is run after being closed by the user or even launched from back suspended state. Here’s a little history on this whole ‘suspended’ state of a Metro Style app: Once the user say, ‘alt+tab...(read more)

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  • Metro: Introduction to the WinJS ListView Control

    - by Stephen.Walther
    The goal of this blog entry is to provide a quick introduction to the ListView control – just the bare minimum that you need to know to start using the control. When building Metro style applications using JavaScript, the ListView control is the primary control that you use for displaying lists of items. For example, if you are building a product catalog app, then you can use the ListView control to display the list of products. The ListView control supports several advanced features that I plan to discuss in future blog entries. For example, you can group the items in a ListView, you can create master/details views with a ListView, and you can efficiently work with large sets of items with a ListView. In this blog entry, we’ll keep things simple and focus on displaying a list of products. There are three things that you need to do in order to display a list of items with a ListView: Create a data source Create an Item Template Declare the ListView Creating the ListView Data Source The first step is to create (or retrieve) the data that you want to display with the ListView. In most scenarios, you will want to bind a ListView to a WinJS.Binding.List object. The nice thing about the WinJS.Binding.List object is that it enables you to take a standard JavaScript array and convert the array into something that can be bound to the ListView. It doesn’t matter where the JavaScript array comes from. It could be a static array that you declare or you could retrieve the array as the result of an Ajax call to a remote server. The following JavaScript file – named products.js – contains a list of products which can be bound to a ListView. (function () { "use strict"; var products = new WinJS.Binding.List([ { name: "Milk", price: 2.44 }, { name: "Oranges", price: 1.99 }, { name: "Wine", price: 8.55 }, { name: "Apples", price: 2.44 }, { name: "Steak", price: 1.99 }, { name: "Eggs", price: 2.44 }, { name: "Mushrooms", price: 1.99 }, { name: "Yogurt", price: 2.44 }, { name: "Soup", price: 1.99 }, { name: "Cereal", price: 2.44 }, { name: "Pepsi", price: 1.99 } ]); WinJS.Namespace.define("ListViewDemos", { products: products }); })(); The products variable represents a WinJS.Binding.List object. This object is initialized with a plain-old JavaScript array which represents an array of products. To avoid polluting the global namespace, the code above uses the module pattern and exposes the products using a namespace. The list of products is exposed to the world as ListViewDemos.products. To learn more about the module pattern and namespaces in WinJS, see my earlier blog entry: http://stephenwalther.com/blog/archive/2012/02/22/metro-namespaces-and-modules.aspx Creating the ListView Item Template The ListView control does not know how to render anything. It doesn’t know how you want each list item to appear. To get the ListView control to render something useful, you must create an Item Template. Here’s what our template for rendering an individual product looks like: <div id="productTemplate" data-win-control="WinJS.Binding.Template"> <div class="product"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> </div> This template displays the product name and price from the data source. Normally, you will declare your template in the same file as you declare the ListView control. In our case, both the template and ListView are declared in the default.html file. To learn more about templates, see my earlier blog entry: http://stephenwalther.com/blog/archive/2012/02/27/metro-using-templates.aspx Declaring the ListView The final step is to declare the ListView control in a page. Here’s the markup for declaring a ListView: <div data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource:ListViewDemos.products.dataSource, itemTemplate:select('#productTemplate') }"> </div> You declare a ListView by adding the data-win-control to an HTML DIV tag. The data-win-options attribute is used to set two properties of the ListView. The ListView is associated with its data source with the itemDataSource property. Notice that the data source is ListViewDemos.products.dataSource and not just ListViewDemos.products. You need to associate the ListView with the dataSoure property. The ListView is associated with its item template with the help of the itemTemplate property. The ID of the item template — #productTemplate – is used to select the template from the page. Here’s what the complete version of the default.html page looks like: <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>ListViewDemos</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- ListViewDemos references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> <script src="/js/products.js" type="text/javascript"></script> <style type="text/css"> .product { width: 200px; height: 100px; border: white solid 1px; } </style> </head> <body> <div id="productTemplate" data-win-control="WinJS.Binding.Template"> <div class="product"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> </div> <div data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource:ListViewDemos.products.dataSource, itemTemplate:select('#productTemplate') }"> </div> </body> </html> Notice that the page above includes a reference to the products.js file: <script src=”/js/products.js” type=”text/javascript”></script> The page above also contains a Template control which contains the ListView item template. Finally, the page includes the declaration of the ListView control. Summary The goal of this blog entry was to describe the minimal set of steps which you must complete to use the WinJS ListView control to display a simple list of items. You learned how to create a data source, declare an item template, and declare a ListView control.

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  • Metro: Introduction to the WinJS ListView Control

    - by Stephen.Walther
    The goal of this blog entry is to provide a quick introduction to the ListView control – just the bare minimum that you need to know to start using the control. When building Metro style applications using JavaScript, the ListView control is the primary control that you use for displaying lists of items. For example, if you are building a product catalog app, then you can use the ListView control to display the list of products. The ListView control supports several advanced features that I plan to discuss in future blog entries. For example, you can group the items in a ListView, you can create master/details views with a ListView, and you can efficiently work with large sets of items with a ListView. In this blog entry, we’ll keep things simple and focus on displaying a list of products. There are three things that you need to do in order to display a list of items with a ListView: Create a data source Create an Item Template Declare the ListView Creating the ListView Data Source The first step is to create (or retrieve) the data that you want to display with the ListView. In most scenarios, you will want to bind a ListView to a WinJS.Binding.List object. The nice thing about the WinJS.Binding.List object is that it enables you to take a standard JavaScript array and convert the array into something that can be bound to the ListView. It doesn’t matter where the JavaScript array comes from. It could be a static array that you declare or you could retrieve the array as the result of an Ajax call to a remote server. The following JavaScript file – named products.js – contains a list of products which can be bound to a ListView. (function () { "use strict"; var products = new WinJS.Binding.List([ { name: "Milk", price: 2.44 }, { name: "Oranges", price: 1.99 }, { name: "Wine", price: 8.55 }, { name: "Apples", price: 2.44 }, { name: "Steak", price: 1.99 }, { name: "Eggs", price: 2.44 }, { name: "Mushrooms", price: 1.99 }, { name: "Yogurt", price: 2.44 }, { name: "Soup", price: 1.99 }, { name: "Cereal", price: 2.44 }, { name: "Pepsi", price: 1.99 } ]); WinJS.Namespace.define("ListViewDemos", { products: products }); })(); The products variable represents a WinJS.Binding.List object. This object is initialized with a plain-old JavaScript array which represents an array of products. To avoid polluting the global namespace, the code above uses the module pattern and exposes the products using a namespace. The list of products is exposed to the world as ListViewDemos.products. To learn more about the module pattern and namespaces in WinJS, see my earlier blog entry: http://stephenwalther.com/blog/archive/2012/02/22/metro-namespaces-and-modules.aspx Creating the ListView Item Template The ListView control does not know how to render anything. It doesn’t know how you want each list item to appear. To get the ListView control to render something useful, you must create an Item Template. Here’s what our template for rendering an individual product looks like: <div id="productTemplate" data-win-control="WinJS.Binding.Template"> <div class="product"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> </div> This template displays the product name and price from the data source. Normally, you will declare your template in the same file as you declare the ListView control. In our case, both the template and ListView are declared in the default.html file. To learn more about templates, see my earlier blog entry: http://stephenwalther.com/blog/archive/2012/02/27/metro-using-templates.aspx Declaring the ListView The final step is to declare the ListView control in a page. Here’s the markup for declaring a ListView: <div data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource:ListViewDemos.products.dataSource, itemTemplate:select('#productTemplate') }"> </div> You declare a ListView by adding the data-win-control to an HTML DIV tag. The data-win-options attribute is used to set two properties of the ListView. The ListView is associated with its data source with the itemDataSource property. Notice that the data source is ListViewDemos.products.dataSource and not just ListViewDemos.products. You need to associate the ListView with the dataSoure property. The ListView is associated with its item template with the help of the itemTemplate property. The ID of the item template — #productTemplate – is used to select the template from the page. Here’s what the complete version of the default.html page looks like: <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>ListViewDemos</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- ListViewDemos references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> <script src="/js/products.js" type="text/javascript"></script> <style type="text/css"> .product { width: 200px; height: 100px; border: white solid 1px; } </style> </head> <body> <div id="productTemplate" data-win-control="WinJS.Binding.Template"> <div class="product"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> </div> <div data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource:ListViewDemos.products.dataSource, itemTemplate:select('#productTemplate') }"> </div> </body> </html> Notice that the page above includes a reference to the products.js file: <script src=”/js/products.js” type=”text/javascript”></script> The page above also contains a Template control which contains the ListView item template. Finally, the page includes the declaration of the ListView control. Summary The goal of this blog entry was to describe the minimal set of steps which you must complete to use the WinJS ListView control to display a simple list of items. You learned how to create a data source, declare an item template, and declare a ListView control.

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  • Code and Slides: Getting Started Building Windows 8 HTML/JavaScript Metro Apps

    - by dwahlin
    This presentation is from a talk I gave at the spring 2012 DevConnections conference. It covers some of the key topics you need to know to get started building Windows 8 HTML/JavaScript Metro apps including navigation options, UI surfaces that can be used, controls, data binding and templates, and animations. View more of my presentations here. Sample code shown in the presentation can be found here. A large number of samples are available in the Windows 8 SDK which can be found here.

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  • Metro: Introduction to CSS 3 Grid Layout

    - by Stephen.Walther
    The purpose of this blog post is to provide you with a quick introduction to the new W3C CSS 3 Grid Layout standard. You can use CSS Grid Layout in Metro style applications written with JavaScript to lay out the content of an HTML page. CSS Grid Layout provides you with all of the benefits of using HTML tables for layout without requiring you to actually use any HTML table elements. Doing Page Layouts without Tables Back in the 1990’s, if you wanted to create a fancy website, then you would use HTML tables for layout. For example, if you wanted to create a standard three-column page layout then you would create an HTML table with three columns like this: <table height="100%"> <tr> <td valign="top" width="300px" bgcolor="red"> Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column </td> <td valign="top" bgcolor="green"> Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column </td> <td valign="top" width="300px" bgcolor="blue"> Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column </td> </tr> </table> When the table above gets rendered out to a browser, you end up with the following three-column layout: The width of the left and right columns is fixed – the width of the middle column expands or contracts depending on the width of the browser. Sometime around the year 2005, everyone decided that using tables for layout was a bad idea. Instead of using tables for layout — it was collectively decided by the spirit of the Web — you should use Cascading Style Sheets instead. Why is using HTML tables for layout bad? Using tables for layout breaks the semantics of the TABLE element. A TABLE element should be used only for displaying tabular information such as train schedules or moon phases. Using tables for layout is bad for accessibility (The Web Content Accessibility Guidelines 1.0 is explicit about this) and using tables for layout is bad for separating content from layout (see http://CSSZenGarden.com). Post 2005, anyone who used HTML tables for layout were encouraged to hold their heads down in shame. That’s all well and good, but the problem with using CSS for layout is that it can be more difficult to work with CSS than HTML tables. For example, to achieve a standard three-column layout, you either need to use absolute positioning or floats. Here’s a three-column layout with floats: <style type="text/css"> #container { min-width: 800px; } #leftColumn { float: left; width: 300px; height: 100%; background-color:red; } #middleColumn { background-color:green; height: 100%; } #rightColumn { float: right; width: 300px; height: 100%; background-color:blue; } </style> <div id="container"> <div id="rightColumn"> Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column </div> <div id="leftColumn"> Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column </div> <div id="middleColumn"> Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column </div> </div> The page above contains four DIV elements: a container DIV which contains a leftColumn, middleColumn, and rightColumn DIV. The leftColumn DIV element is floated to the left and the rightColumn DIV element is floated to the right. Notice that the rightColumn DIV appears in the page before the middleColumn DIV – this unintuitive ordering is necessary to get the floats to work correctly (see http://stackoverflow.com/questions/533607/css-three-column-layout-problem). The page above (almost) works with the most recent versions of most browsers. For example, you get the correct three-column layout in both Firefox and Chrome: And the layout mostly works with Internet Explorer 9 except for the fact that for some strange reason the min-width doesn’t work so when you shrink the width of your browser, you can get the following unwanted layout: Notice how the middle column (the green column) bleeds to the left and right. People have solved these issues with more complicated CSS. For example, see: http://matthewjamestaylor.com/blog/holy-grail-no-quirks-mode.htm But, at this point, no one could argue that using CSS is easier or more intuitive than tables. It takes work to get a layout with CSS and we know that we could achieve the same layout more easily using HTML tables. Using CSS Grid Layout CSS Grid Layout is a new W3C standard which provides you with all of the benefits of using HTML tables for layout without the disadvantage of using an HTML TABLE element. In other words, CSS Grid Layout enables you to perform table layouts using pure Cascading Style Sheets. The CSS Grid Layout standard is still in a “Working Draft” state (it is not finalized) and it is located here: http://www.w3.org/TR/css3-grid-layout/ The CSS Grid Layout standard is only supported by Internet Explorer 10 and there are no signs that any browser other than Internet Explorer will support this standard in the near future. This means that it is only practical to take advantage of CSS Grid Layout when building Metro style applications with JavaScript. Here’s how you can create a standard three-column layout using a CSS Grid Layout: <!DOCTYPE html> <html> <head> <style type="text/css"> html, body, #container { height: 100%; padding: 0px; margin: 0px; } #container { display: -ms-grid; -ms-grid-columns: 300px auto 300px; -ms-grid-rows: 100%; } #leftColumn { -ms-grid-column: 1; background-color:red; } #middleColumn { -ms-grid-column: 2; background-color:green; } #rightColumn { -ms-grid-column: 3; background-color:blue; } </style> </head> <body> <div id="container"> <div id="leftColumn"> Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column </div> <div id="middleColumn"> Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column </div> <div id="rightColumn"> Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column </div> </div> </body> </html> When the page above is rendered in Internet Explorer 10, you get a standard three-column layout: The page above contains four DIV elements: a container DIV which contains a leftColumn DIV, middleColumn DIV, and rightColumn DIV. The container DIV is set to Grid display mode with the following CSS rule: #container { display: -ms-grid; -ms-grid-columns: 300px auto 300px; -ms-grid-rows: 100%; } The display property is set to the value “-ms-grid”. This property causes the container DIV to lay out its child elements in a grid. (Notice that you use “-ms-grid” instead of “grid”. The “-ms-“ prefix is used because the CSS Grid Layout standard is still preliminary. This implementation only works with IE10 and it might change before the final release.) The grid columns and rows are defined with the “-ms-grid-columns” and “-ms-grid-rows” properties. The style rule above creates a grid with three columns and one row. The left and right columns are fixed sized at 300 pixels. The middle column sizes automatically depending on the remaining space available. The leftColumn, middleColumn, and rightColumn DIVs are positioned within the container grid element with the following CSS rules: #leftColumn { -ms-grid-column: 1; background-color:red; } #middleColumn { -ms-grid-column: 2; background-color:green; } #rightColumn { -ms-grid-column: 3; background-color:blue; } The “-ms-grid-column” property is used to specify the column associated with the element selected by the style sheet selector. The leftColumn DIV is positioned in the first grid column, the middleColumn DIV is positioned in the second grid column, and the rightColumn DIV is positioned in the third grid column. I find using CSS Grid Layout to be just as intuitive as using an HTML table for layout. You define your columns and rows and then you position different elements within these columns and rows. Very straightforward. Creating Multiple Columns and Rows In the previous section, we created a super simple three-column layout. This layout contained only a single row. In this section, let’s create a slightly more complicated layout which contains more than one row: The following page contains a header row, a content row, and a footer row. The content row contains three columns: <!DOCTYPE html> <html> <head> <style type="text/css"> html, body, #container { height: 100%; padding: 0px; margin: 0px; } #container { display: -ms-grid; -ms-grid-columns: 300px auto 300px; -ms-grid-rows: 100px 1fr 100px; } #header { -ms-grid-column: 1; -ms-grid-column-span: 3; -ms-grid-row: 1; background-color: yellow; } #leftColumn { -ms-grid-column: 1; -ms-grid-row: 2; background-color:red; } #middleColumn { -ms-grid-column: 2; -ms-grid-row: 2; background-color:green; } #rightColumn { -ms-grid-column: 3; -ms-grid-row: 2; background-color:blue; } #footer { -ms-grid-column: 1; -ms-grid-column-span: 3; -ms-grid-row: 3; background-color: orange; } </style> </head> <body> <div id="container"> <div id="header"> Header, Header, Header </div> <div id="leftColumn"> Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column </div> <div id="middleColumn"> Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column </div> <div id="rightColumn"> Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column </div> <div id="footer"> Footer, Footer, Footer </div> </div> </body> </html> In the page above, the grid layout is created with the following rule which creates a grid with three rows and three columns: #container { display: -ms-grid; -ms-grid-columns: 300px auto 300px; -ms-grid-rows: 100px 1fr 100px; } The header is created with the following rule: #header { -ms-grid-column: 1; -ms-grid-column-span: 3; -ms-grid-row: 1; background-color: yellow; } The header is positioned in column 1 and row 1. Furthermore, notice that the “-ms-grid-column-span” property is used to span the header across three columns. CSS Grid Layout and Fractional Units When you use CSS Grid Layout, you can take advantage of fractional units. Fractional units provide you with an easy way of dividing up remaining space in a page. Imagine, for example, that you want to create a three-column page layout. You want the size of the first column to be fixed at 200 pixels and you want to divide the remaining space among the remaining three columns. The width of the second column is equal to the combined width of the third and fourth columns. The following CSS rule creates four columns with the desired widths: #container { display: -ms-grid; -ms-grid-columns: 200px 2fr 1fr 1fr; -ms-grid-rows: 1fr; } The fr unit represents a fraction. The grid above contains four columns. The second column is two times the size (2fr) of the third (1fr) and fourth (1fr) columns. When you use the fractional unit, the remaining space is divided up using fractional amounts. Notice that the single row is set to a height of 1fr. The single grid row gobbles up the entire vertical space. Here’s the entire HTML page: <!DOCTYPE html> <html> <head> <style type="text/css"> html, body, #container { height: 100%; padding: 0px; margin: 0px; } #container { display: -ms-grid; -ms-grid-columns: 200px 2fr 1fr 1fr; -ms-grid-rows: 1fr; } #firstColumn { -ms-grid-column: 1; background-color:red; } #secondColumn { -ms-grid-column: 2; background-color:green; } #thirdColumn { -ms-grid-column: 3; background-color:blue; } #fourthColumn { -ms-grid-column: 4; background-color:orange; } </style> </head> <body> <div id="container"> <div id="firstColumn"> First Column, First Column, First Column </div> <div id="secondColumn"> Second Column, Second Column, Second Column </div> <div id="thirdColumn"> Third Column, Third Column, Third Column </div> <div id="fourthColumn"> Fourth Column, Fourth Column, Fourth Column </div> </div> </body> </html>   Summary There is more in the CSS 3 Grid Layout standard than discussed in this blog post. My goal was to describe the basics. If you want to learn more than you can read through the entire standard at http://www.w3.org/TR/css3-grid-layout/ In this blog post, I described some of the difficulties that you might encounter when attempting to replace HTML tables with Cascading Style Sheets when laying out a web page. I explained how you can take advantage of the CSS 3 Grid Layout standard to avoid these problems when building Metro style applications using JavaScript. CSS 3 Grid Layout provides you with all of the benefits of using HTML tables for laying out a page without requiring you to use HTML table elements.

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  • Metro: Introduction to CSS 3 Grid Layout

    - by Stephen.Walther
    The purpose of this blog post is to provide you with a quick introduction to the new W3C CSS 3 Grid Layout standard. You can use CSS Grid Layout in Metro style applications written with JavaScript to lay out the content of an HTML page. CSS Grid Layout provides you with all of the benefits of using HTML tables for layout without requiring you to actually use any HTML table elements. Doing Page Layouts without Tables Back in the 1990’s, if you wanted to create a fancy website, then you would use HTML tables for layout. For example, if you wanted to create a standard three-column page layout then you would create an HTML table with three columns like this: <table height="100%"> <tr> <td valign="top" width="300px" bgcolor="red"> Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column </td> <td valign="top" bgcolor="green"> Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column </td> <td valign="top" width="300px" bgcolor="blue"> Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column </td> </tr> </table> When the table above gets rendered out to a browser, you end up with the following three-column layout: The width of the left and right columns is fixed – the width of the middle column expands or contracts depending on the width of the browser. Sometime around the year 2005, everyone decided that using tables for layout was a bad idea. Instead of using tables for layout — it was collectively decided by the spirit of the Web — you should use Cascading Style Sheets instead. Why is using HTML tables for layout bad? Using tables for layout breaks the semantics of the TABLE element. A TABLE element should be used only for displaying tabular information such as train schedules or moon phases. Using tables for layout is bad for accessibility (The Web Content Accessibility Guidelines 1.0 is explicit about this) and using tables for layout is bad for separating content from layout (see http://CSSZenGarden.com). Post 2005, anyone who used HTML tables for layout were encouraged to hold their heads down in shame. That’s all well and good, but the problem with using CSS for layout is that it can be more difficult to work with CSS than HTML tables. For example, to achieve a standard three-column layout, you either need to use absolute positioning or floats. Here’s a three-column layout with floats: <style type="text/css"> #container { min-width: 800px; } #leftColumn { float: left; width: 300px; height: 100%; background-color:red; } #middleColumn { background-color:green; height: 100%; } #rightColumn { float: right; width: 300px; height: 100%; background-color:blue; } </style> <div id="container"> <div id="rightColumn"> Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column </div> <div id="leftColumn"> Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column </div> <div id="middleColumn"> Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column </div> </div> The page above contains four DIV elements: a container DIV which contains a leftColumn, middleColumn, and rightColumn DIV. The leftColumn DIV element is floated to the left and the rightColumn DIV element is floated to the right. Notice that the rightColumn DIV appears in the page before the middleColumn DIV – this unintuitive ordering is necessary to get the floats to work correctly (see http://stackoverflow.com/questions/533607/css-three-column-layout-problem). The page above (almost) works with the most recent versions of most browsers. For example, you get the correct three-column layout in both Firefox and Chrome: And the layout mostly works with Internet Explorer 9 except for the fact that for some strange reason the min-width doesn’t work so when you shrink the width of your browser, you can get the following unwanted layout: Notice how the middle column (the green column) bleeds to the left and right. People have solved these issues with more complicated CSS. For example, see: http://matthewjamestaylor.com/blog/holy-grail-no-quirks-mode.htm But, at this point, no one could argue that using CSS is easier or more intuitive than tables. It takes work to get a layout with CSS and we know that we could achieve the same layout more easily using HTML tables. Using CSS Grid Layout CSS Grid Layout is a new W3C standard which provides you with all of the benefits of using HTML tables for layout without the disadvantage of using an HTML TABLE element. In other words, CSS Grid Layout enables you to perform table layouts using pure Cascading Style Sheets. The CSS Grid Layout standard is still in a “Working Draft” state (it is not finalized) and it is located here: http://www.w3.org/TR/css3-grid-layout/ The CSS Grid Layout standard is only supported by Internet Explorer 10 and there are no signs that any browser other than Internet Explorer will support this standard in the near future. This means that it is only practical to take advantage of CSS Grid Layout when building Metro style applications with JavaScript. Here’s how you can create a standard three-column layout using a CSS Grid Layout: <!DOCTYPE html> <html> <head> <style type="text/css"> html, body, #container { height: 100%; padding: 0px; margin: 0px; } #container { display: -ms-grid; -ms-grid-columns: 300px auto 300px; -ms-grid-rows: 100%; } #leftColumn { -ms-grid-column: 1; background-color:red; } #middleColumn { -ms-grid-column: 2; background-color:green; } #rightColumn { -ms-grid-column: 3; background-color:blue; } </style> </head> <body> <div id="container"> <div id="leftColumn"> Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column </div> <div id="middleColumn"> Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column </div> <div id="rightColumn"> Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column </div> </div> </body> </html> When the page above is rendered in Internet Explorer 10, you get a standard three-column layout: The page above contains four DIV elements: a container DIV which contains a leftColumn DIV, middleColumn DIV, and rightColumn DIV. The container DIV is set to Grid display mode with the following CSS rule: #container { display: -ms-grid; -ms-grid-columns: 300px auto 300px; -ms-grid-rows: 100%; } The display property is set to the value “-ms-grid”. This property causes the container DIV to lay out its child elements in a grid. (Notice that you use “-ms-grid” instead of “grid”. The “-ms-“ prefix is used because the CSS Grid Layout standard is still preliminary. This implementation only works with IE10 and it might change before the final release.) The grid columns and rows are defined with the “-ms-grid-columns” and “-ms-grid-rows” properties. The style rule above creates a grid with three columns and one row. The left and right columns are fixed sized at 300 pixels. The middle column sizes automatically depending on the remaining space available. The leftColumn, middleColumn, and rightColumn DIVs are positioned within the container grid element with the following CSS rules: #leftColumn { -ms-grid-column: 1; background-color:red; } #middleColumn { -ms-grid-column: 2; background-color:green; } #rightColumn { -ms-grid-column: 3; background-color:blue; } The “-ms-grid-column” property is used to specify the column associated with the element selected by the style sheet selector. The leftColumn DIV is positioned in the first grid column, the middleColumn DIV is positioned in the second grid column, and the rightColumn DIV is positioned in the third grid column. I find using CSS Grid Layout to be just as intuitive as using an HTML table for layout. You define your columns and rows and then you position different elements within these columns and rows. Very straightforward. Creating Multiple Columns and Rows In the previous section, we created a super simple three-column layout. This layout contained only a single row. In this section, let’s create a slightly more complicated layout which contains more than one row: The following page contains a header row, a content row, and a footer row. The content row contains three columns: <!DOCTYPE html> <html> <head> <style type="text/css"> html, body, #container { height: 100%; padding: 0px; margin: 0px; } #container { display: -ms-grid; -ms-grid-columns: 300px auto 300px; -ms-grid-rows: 100px 1fr 100px; } #header { -ms-grid-column: 1; -ms-grid-column-span: 3; -ms-grid-row: 1; background-color: yellow; } #leftColumn { -ms-grid-column: 1; -ms-grid-row: 2; background-color:red; } #middleColumn { -ms-grid-column: 2; -ms-grid-row: 2; background-color:green; } #rightColumn { -ms-grid-column: 3; -ms-grid-row: 2; background-color:blue; } #footer { -ms-grid-column: 1; -ms-grid-column-span: 3; -ms-grid-row: 3; background-color: orange; } </style> </head> <body> <div id="container"> <div id="header"> Header, Header, Header </div> <div id="leftColumn"> Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column, Left Column </div> <div id="middleColumn"> Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column, Middle Column </div> <div id="rightColumn"> Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column, Right Column </div> <div id="footer"> Footer, Footer, Footer </div> </div> </body> </html> In the page above, the grid layout is created with the following rule which creates a grid with three rows and three columns: #container { display: -ms-grid; -ms-grid-columns: 300px auto 300px; -ms-grid-rows: 100px 1fr 100px; } The header is created with the following rule: #header { -ms-grid-column: 1; -ms-grid-column-span: 3; -ms-grid-row: 1; background-color: yellow; } The header is positioned in column 1 and row 1. Furthermore, notice that the “-ms-grid-column-span” property is used to span the header across three columns. CSS Grid Layout and Fractional Units When you use CSS Grid Layout, you can take advantage of fractional units. Fractional units provide you with an easy way of dividing up remaining space in a page. Imagine, for example, that you want to create a three-column page layout. You want the size of the first column to be fixed at 200 pixels and you want to divide the remaining space among the remaining three columns. The width of the second column is equal to the combined width of the third and fourth columns. The following CSS rule creates four columns with the desired widths: #container { display: -ms-grid; -ms-grid-columns: 200px 2fr 1fr 1fr; -ms-grid-rows: 1fr; } The fr unit represents a fraction. The grid above contains four columns. The second column is two times the size (2fr) of the third (1fr) and fourth (1fr) columns. When you use the fractional unit, the remaining space is divided up using fractional amounts. Notice that the single row is set to a height of 1fr. The single grid row gobbles up the entire vertical space. Here’s the entire HTML page: <!DOCTYPE html> <html> <head> <style type="text/css"> html, body, #container { height: 100%; padding: 0px; margin: 0px; } #container { display: -ms-grid; -ms-grid-columns: 200px 2fr 1fr 1fr; -ms-grid-rows: 1fr; } #firstColumn { -ms-grid-column: 1; background-color:red; } #secondColumn { -ms-grid-column: 2; background-color:green; } #thirdColumn { -ms-grid-column: 3; background-color:blue; } #fourthColumn { -ms-grid-column: 4; background-color:orange; } </style> </head> <body> <div id="container"> <div id="firstColumn"> First Column, First Column, First Column </div> <div id="secondColumn"> Second Column, Second Column, Second Column </div> <div id="thirdColumn"> Third Column, Third Column, Third Column </div> <div id="fourthColumn"> Fourth Column, Fourth Column, Fourth Column </div> </div> </body> </html>   Summary There is more in the CSS 3 Grid Layout standard than discussed in this blog post. My goal was to describe the basics. If you want to learn more than you can read through the entire standard at http://www.w3.org/TR/css3-grid-layout/ In this blog post, I described some of the difficulties that you might encounter when attempting to replace HTML tables with Cascading Style Sheets when laying out a web page. I explained how you can take advantage of the CSS 3 Grid Layout standard to avoid these problems when building Metro style applications using JavaScript. CSS 3 Grid Layout provides you with all of the benefits of using HTML tables for laying out a page without requiring you to use HTML table elements.

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  • metro style on windows and android

    - by MRM
    I want to develop a rather simple app using windows 8 metro style for GUI. But i need this app to have the same appearance, GUI, for both platforms, so that end users that uses it both on PC and a mobile device to have the same visual experience and a flawless navigation. So, does anyone have knowledge of a Java framework or library to satisfy these needs? Or maybe a method to create a web-based app using HTML, PHP, JScript etc. (maybe something using a local server, on the same machine, because a web server is out of discussion, at least for the moment)? Any idea, method, technology related to the subject is also helpful. And if what you are thinking at can be used for IOS too, the better.

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  • Metro: Creating an IndexedDbDataSource for WinJS

    - by Stephen.Walther
    The goal of this blog entry is to describe how you can create custom data sources which you can use with the controls in the WinJS library. In particular, I explain how you can create an IndexedDbDataSource which you can use to store and retrieve data from an IndexedDB database. If you want to skip ahead, and ignore all of the fascinating content in-between, I’ve included the complete code for the IndexedDbDataSource at the very bottom of this blog entry. What is IndexedDB? IndexedDB is a database in the browser. You can use the IndexedDB API with all modern browsers including Firefox, Chrome, and Internet Explorer 10. And, of course, you can use IndexedDB with Metro style apps written with JavaScript. If you need to persist data in a Metro style app written with JavaScript then IndexedDB is a good option. Each Metro app can only interact with its own IndexedDB databases. And, IndexedDB provides you with transactions, indices, and cursors – the elements of any modern database. An IndexedDB database might be different than the type of database that you normally use. An IndexedDB database is an object-oriented database and not a relational database. Instead of storing data in tables, you store data in object stores. You store JavaScript objects in an IndexedDB object store. You create new IndexedDB object stores by handling the upgradeneeded event when you attempt to open a connection to an IndexedDB database. For example, here’s how you would both open a connection to an existing database named TasksDB and create the TasksDB database when it does not already exist: var reqOpen = window.indexedDB.open(“TasksDB”, 2); reqOpen.onupgradeneeded = function (evt) { var newDB = evt.target.result; newDB.createObjectStore("tasks", { keyPath: "id", autoIncrement: true }); }; reqOpen.onsuccess = function () { var db = reqOpen.result; // Do something with db }; When you call window.indexedDB.open(), and the database does not already exist, then the upgradeneeded event is raised. In the code above, the upgradeneeded handler creates a new object store named tasks. The new object store has an auto-increment column named id which acts as the primary key column. If the database already exists with the right version, and you call window.indexedDB.open(), then the success event is raised. At that point, you have an open connection to the existing database and you can start doing something with the database. You use asynchronous methods to interact with an IndexedDB database. For example, the following code illustrates how you would add a new object to the tasks object store: var transaction = db.transaction(“tasks”, “readwrite”); var reqAdd = transaction.objectStore(“tasks”).add({ name: “Feed the dog” }); reqAdd.onsuccess = function() { // Tasks added successfully }; The code above creates a new database transaction, adds a new task to the tasks object store, and handles the success event. If the new task gets added successfully then the success event is raised. Creating a WinJS IndexedDbDataSource The most powerful control in the WinJS library is the ListView control. This is the control that you use to display a collection of items. If you want to display data with a ListView control, you need to bind the control to a data source. The WinJS library includes two objects which you can use as a data source: the List object and the StorageDataSource object. The List object enables you to represent a JavaScript array as a data source and the StorageDataSource enables you to represent the file system as a data source. If you want to bind an IndexedDB database to a ListView then you have a choice. You can either dump the items from the IndexedDB database into a List object or you can create a custom data source. I explored the first approach in a previous blog entry. In this blog entry, I explain how you can create a custom IndexedDB data source. Implementing the IListDataSource Interface You create a custom data source by implementing the IListDataSource interface. This interface contains the contract for the methods which the ListView needs to interact with a data source. The easiest way to implement the IListDataSource interface is to derive a new object from the base VirtualizedDataSource object. The VirtualizedDataSource object requires a data adapter which implements the IListDataAdapter interface. Yes, because of the number of objects involved, this is a little confusing. Your code ends up looking something like this: var IndexedDbDataSource = WinJS.Class.derive( WinJS.UI.VirtualizedDataSource, function (dbName, dbVersion, objectStoreName, upgrade, error) { this._adapter = new IndexedDbDataAdapter(dbName, dbVersion, objectStoreName, upgrade, error); this._baseDataSourceConstructor(this._adapter); }, { nuke: function () { this._adapter.nuke(); }, remove: function (key) { this._adapter.removeInternal(key); } } ); The code above is used to create a new class named IndexedDbDataSource which derives from the base VirtualizedDataSource class. In the constructor for the new class, the base class _baseDataSourceConstructor() method is called. A data adapter is passed to the _baseDataSourceConstructor() method. The code above creates a new method exposed by the IndexedDbDataSource named nuke(). The nuke() method deletes all of the objects from an object store. The code above also overrides a method named remove(). Our derived remove() method accepts any type of key and removes the matching item from the object store. Almost all of the work of creating a custom data source goes into building the data adapter class. The data adapter class implements the IListDataAdapter interface which contains the following methods: · change() · getCount() · insertAfter() · insertAtEnd() · insertAtStart() · insertBefore() · itemsFromDescription() · itemsFromEnd() · itemsFromIndex() · itemsFromKey() · itemsFromStart() · itemSignature() · moveAfter() · moveBefore() · moveToEnd() · moveToStart() · remove() · setNotificationHandler() · compareByIdentity Fortunately, you are not required to implement all of these methods. You only need to implement the methods that you actually need. In the case of the IndexedDbDataSource, I implemented the getCount(), itemsFromIndex(), insertAtEnd(), and remove() methods. If you are creating a read-only data source then you really only need to implement the getCount() and itemsFromIndex() methods. Implementing the getCount() Method The getCount() method returns the total number of items from the data source. So, if you are storing 10,000 items in an object store then this method would return the value 10,000. Here’s how I implemented the getCount() method: getCount: function () { var that = this; return new WinJS.Promise(function (complete, error) { that._getObjectStore().then(function (store) { var reqCount = store.count(); reqCount.onerror = that._error; reqCount.onsuccess = function (evt) { complete(evt.target.result); }; }); }); } The first thing that you should notice is that the getCount() method returns a WinJS promise. This is a requirement. The getCount() method is asynchronous which is a good thing because all of the IndexedDB methods (at least the methods implemented in current browsers) are also asynchronous. The code above retrieves an object store and then uses the IndexedDB count() method to get a count of the items in the object store. The value is returned from the promise by calling complete(). Implementing the itemsFromIndex method When a ListView displays its items, it calls the itemsFromIndex() method. By default, it calls this method multiple times to get different ranges of items. Three parameters are passed to the itemsFromIndex() method: the requestIndex, countBefore, and countAfter parameters. The requestIndex indicates the index of the item from the database to show. The countBefore and countAfter parameters represent hints. These are integer values which represent the number of items before and after the requestIndex to retrieve. Again, these are only hints and you can return as many items before and after the request index as you please. Here’s how I implemented the itemsFromIndex method: itemsFromIndex: function (requestIndex, countBefore, countAfter) { var that = this; return new WinJS.Promise(function (complete, error) { that.getCount().then(function (count) { if (requestIndex >= count) { return WinJS.Promise.wrapError(new WinJS.ErrorFromName(WinJS.UI.FetchError.doesNotExist)); } var startIndex = Math.max(0, requestIndex - countBefore); var endIndex = Math.min(count, requestIndex + countAfter + 1); that._getObjectStore().then(function (store) { var index = 0; var items = []; var req = store.openCursor(); req.onerror = that._error; req.onsuccess = function (evt) { var cursor = evt.target.result; if (index < startIndex) { index = startIndex; cursor.advance(startIndex); return; } if (cursor && index < endIndex) { index++; items.push({ key: cursor.value[store.keyPath].toString(), data: cursor.value }); cursor.continue(); return; } results = { items: items, offset: requestIndex - startIndex, totalCount: count }; complete(results); }; }); }); }); } In the code above, a cursor is used to iterate through the objects in an object store. You fetch the next item in the cursor by calling either the cursor.continue() or cursor.advance() method. The continue() method moves forward by one object and the advance() method moves forward a specified number of objects. Each time you call continue() or advance(), the success event is raised again. If the cursor is null then you know that you have reached the end of the cursor and you can return the results. Some things to be careful about here. First, the return value from the itemsFromIndex() method must implement the IFetchResult interface. In particular, you must return an object which has an items, offset, and totalCount property. Second, each item in the items array must implement the IListItem interface. Each item should have a key and a data property. Implementing the insertAtEnd() Method When creating the IndexedDbDataSource, I wanted to go beyond creating a simple read-only data source and support inserting and deleting objects. If you want to support adding new items with your data source then you need to implement the insertAtEnd() method. Here’s how I implemented the insertAtEnd() method for the IndexedDbDataSource: insertAtEnd:function(unused, data) { var that = this; return new WinJS.Promise(function (complete, error) { that._getObjectStore("readwrite").done(function(store) { var reqAdd = store.add(data); reqAdd.onerror = that._error; reqAdd.onsuccess = function (evt) { var reqGet = store.get(evt.target.result); reqGet.onerror = that._error; reqGet.onsuccess = function (evt) { var newItem = { key:evt.target.result[store.keyPath].toString(), data:evt.target.result } complete(newItem); }; }; }); }); } When implementing the insertAtEnd() method, you need to be careful to return an object which implements the IItem interface. In particular, you should return an object that has a key and a data property. The key must be a string and it uniquely represents the new item added to the data source. The value of the data property represents the new item itself. Implementing the remove() Method Finally, you use the remove() method to remove an item from the data source. You call the remove() method with the key of the item which you want to remove. Implementing the remove() method in the case of the IndexedDbDataSource was a little tricky. The problem is that an IndexedDB object store uses an integer key and the VirtualizedDataSource requires a string key. For that reason, I needed to override the remove() method in the derived IndexedDbDataSource class like this: var IndexedDbDataSource = WinJS.Class.derive( WinJS.UI.VirtualizedDataSource, function (dbName, dbVersion, objectStoreName, upgrade, error) { this._adapter = new IndexedDbDataAdapter(dbName, dbVersion, objectStoreName, upgrade, error); this._baseDataSourceConstructor(this._adapter); }, { nuke: function () { this._adapter.nuke(); }, remove: function (key) { this._adapter.removeInternal(key); } } ); When you call remove(), you end up calling a method of the IndexedDbDataAdapter named removeInternal() . Here’s what the removeInternal() method looks like: setNotificationHandler: function (notificationHandler) { this._notificationHandler = notificationHandler; }, removeInternal: function(key) { var that = this; return new WinJS.Promise(function (complete, error) { that._getObjectStore("readwrite").done(function (store) { var reqDelete = store.delete (key); reqDelete.onerror = that._error; reqDelete.onsuccess = function (evt) { that._notificationHandler.removed(key.toString()); complete(); }; }); }); } The removeInternal() method calls the IndexedDB delete() method to delete an item from the object store. If the item is deleted successfully then the _notificationHandler.remove() method is called. Because we are not implementing the standard IListDataAdapter remove() method, we need to notify the data source (and the ListView control bound to the data source) that an item has been removed. The way that you notify the data source is by calling the _notificationHandler.remove() method. Notice that we get the _notificationHandler in the code above by implementing another method in the IListDataAdapter interface: the setNotificationHandler() method. You can raise the following types of notifications using the _notificationHandler: · beginNotifications() · changed() · endNotifications() · inserted() · invalidateAll() · moved() · removed() · reload() These methods are all part of the IListDataNotificationHandler interface in the WinJS library. Implementing the nuke() Method I wanted to implement a method which would remove all of the items from an object store. Therefore, I created a method named nuke() which calls the IndexedDB clear() method: nuke: function () { var that = this; return new WinJS.Promise(function (complete, error) { that._getObjectStore("readwrite").done(function (store) { var reqClear = store.clear(); reqClear.onerror = that._error; reqClear.onsuccess = function (evt) { that._notificationHandler.reload(); complete(); }; }); }); } Notice that the nuke() method calls the _notificationHandler.reload() method to notify the ListView to reload all of the items from its data source. Because we are implementing a custom method here, we need to use the _notificationHandler to send an update. Using the IndexedDbDataSource To illustrate how you can use the IndexedDbDataSource, I created a simple task list app. You can add new tasks, delete existing tasks, and nuke all of the tasks. You delete an item by selecting an item (swipe or right-click) and clicking the Delete button. Here’s the HTML page which contains the ListView, the form for adding new tasks, and the buttons for deleting and nuking tasks: <!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <title>DataSources</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.1.0.RC/css/ui-dark.css" rel="stylesheet" /> <script src="//Microsoft.WinJS.1.0.RC/js/base.js"></script> <script src="//Microsoft.WinJS.1.0.RC/js/ui.js"></script> <!-- DataSources references --> <link href="indexedDb.css" rel="stylesheet" /> <script type="text/javascript" src="indexedDbDataSource.js"></script> <script src="indexedDb.js"></script> </head> <body> <div id="tmplTask" data-win-control="WinJS.Binding.Template"> <div class="taskItem"> Id: <span data-win-bind="innerText:id"></span> <br /><br /> Name: <span data-win-bind="innerText:name"></span> </div> </div> <div id="lvTasks" data-win-control="WinJS.UI.ListView" data-win-options="{ itemTemplate: select('#tmplTask'), selectionMode: 'single' }"></div> <form id="frmAdd"> <fieldset> <legend>Add Task</legend> <label>New Task</label> <input id="inputTaskName" required /> <button>Add</button> </fieldset> </form> <button id="btnNuke">Nuke</button> <button id="btnDelete">Delete</button> </body> </html> And here is the JavaScript code for the TaskList app: /// <reference path="//Microsoft.WinJS.1.0.RC/js/base.js" /> /// <reference path="//Microsoft.WinJS.1.0.RC/js/ui.js" /> function init() { WinJS.UI.processAll().done(function () { var lvTasks = document.getElementById("lvTasks").winControl; // Bind the ListView to its data source var tasksDataSource = new DataSources.IndexedDbDataSource("TasksDB", 1, "tasks", upgrade); lvTasks.itemDataSource = tasksDataSource; // Wire-up Add, Delete, Nuke buttons document.getElementById("frmAdd").addEventListener("submit", function (evt) { evt.preventDefault(); tasksDataSource.beginEdits(); tasksDataSource.insertAtEnd(null, { name: document.getElementById("inputTaskName").value }).done(function (newItem) { tasksDataSource.endEdits(); document.getElementById("frmAdd").reset(); lvTasks.ensureVisible(newItem.index); }); }); document.getElementById("btnDelete").addEventListener("click", function () { if (lvTasks.selection.count() == 1) { lvTasks.selection.getItems().done(function (items) { tasksDataSource.remove(items[0].data.id); }); } }); document.getElementById("btnNuke").addEventListener("click", function () { tasksDataSource.nuke(); }); // This method is called to initialize the IndexedDb database function upgrade(evt) { var newDB = evt.target.result; newDB.createObjectStore("tasks", { keyPath: "id", autoIncrement: true }); } }); } document.addEventListener("DOMContentLoaded", init); The IndexedDbDataSource is created and bound to the ListView control with the following two lines of code: var tasksDataSource = new DataSources.IndexedDbDataSource("TasksDB", 1, "tasks", upgrade); lvTasks.itemDataSource = tasksDataSource; The IndexedDbDataSource is created with four parameters: the name of the database to create, the version of the database to create, the name of the object store to create, and a function which contains code to initialize the new database. The upgrade function creates a new object store named tasks with an auto-increment property named id: function upgrade(evt) { var newDB = evt.target.result; newDB.createObjectStore("tasks", { keyPath: "id", autoIncrement: true }); } The Complete Code for the IndexedDbDataSource Here’s the complete code for the IndexedDbDataSource: (function () { /************************************************ * The IndexedDBDataAdapter enables you to work * with a HTML5 IndexedDB database. *************************************************/ var IndexedDbDataAdapter = WinJS.Class.define( function (dbName, dbVersion, objectStoreName, upgrade, error) { this._dbName = dbName; // database name this._dbVersion = dbVersion; // database version this._objectStoreName = objectStoreName; // object store name this._upgrade = upgrade; // database upgrade script this._error = error || function (evt) { console.log(evt.message); }; }, { /******************************************* * IListDataAdapter Interface Methods ********************************************/ getCount: function () { var that = this; return new WinJS.Promise(function (complete, error) { that._getObjectStore().then(function (store) { var reqCount = store.count(); reqCount.onerror = that._error; reqCount.onsuccess = function (evt) { complete(evt.target.result); }; }); }); }, itemsFromIndex: function (requestIndex, countBefore, countAfter) { var that = this; return new WinJS.Promise(function (complete, error) { that.getCount().then(function (count) { if (requestIndex >= count) { return WinJS.Promise.wrapError(new WinJS.ErrorFromName(WinJS.UI.FetchError.doesNotExist)); } var startIndex = Math.max(0, requestIndex - countBefore); var endIndex = Math.min(count, requestIndex + countAfter + 1); that._getObjectStore().then(function (store) { var index = 0; var items = []; var req = store.openCursor(); req.onerror = that._error; req.onsuccess = function (evt) { var cursor = evt.target.result; if (index < startIndex) { index = startIndex; cursor.advance(startIndex); return; } if (cursor && index < endIndex) { index++; items.push({ key: cursor.value[store.keyPath].toString(), data: cursor.value }); cursor.continue(); return; } results = { items: items, offset: requestIndex - startIndex, totalCount: count }; complete(results); }; }); }); }); }, insertAtEnd:function(unused, data) { var that = this; return new WinJS.Promise(function (complete, error) { that._getObjectStore("readwrite").done(function(store) { var reqAdd = store.add(data); reqAdd.onerror = that._error; reqAdd.onsuccess = function (evt) { var reqGet = store.get(evt.target.result); reqGet.onerror = that._error; reqGet.onsuccess = function (evt) { var newItem = { key:evt.target.result[store.keyPath].toString(), data:evt.target.result } complete(newItem); }; }; }); }); }, setNotificationHandler: function (notificationHandler) { this._notificationHandler = notificationHandler; }, /***************************************** * IndexedDbDataSource Method ******************************************/ removeInternal: function(key) { var that = this; return new WinJS.Promise(function (complete, error) { that._getObjectStore("readwrite").done(function (store) { var reqDelete = store.delete (key); reqDelete.onerror = that._error; reqDelete.onsuccess = function (evt) { that._notificationHandler.removed(key.toString()); complete(); }; }); }); }, nuke: function () { var that = this; return new WinJS.Promise(function (complete, error) { that._getObjectStore("readwrite").done(function (store) { var reqClear = store.clear(); reqClear.onerror = that._error; reqClear.onsuccess = function (evt) { that._notificationHandler.reload(); complete(); }; }); }); }, /******************************************* * Private Methods ********************************************/ _ensureDbOpen: function () { var that = this; // Try to get cached Db if (that._cachedDb) { return WinJS.Promise.wrap(that._cachedDb); } // Otherwise, open the database return new WinJS.Promise(function (complete, error, progress) { var reqOpen = window.indexedDB.open(that._dbName, that._dbVersion); reqOpen.onerror = function (evt) { error(); }; reqOpen.onupgradeneeded = function (evt) { that._upgrade(evt); that._notificationHandler.invalidateAll(); }; reqOpen.onsuccess = function () { that._cachedDb = reqOpen.result; complete(that._cachedDb); }; }); }, _getObjectStore: function (type) { type = type || "readonly"; var that = this; return new WinJS.Promise(function (complete, error) { that._ensureDbOpen().then(function (db) { var transaction = db.transaction(that._objectStoreName, type); complete(transaction.objectStore(that._objectStoreName)); }); }); }, _get: function (key) { return new WinJS.Promise(function (complete, error) { that._getObjectStore().done(function (store) { var reqGet = store.get(key); reqGet.onerror = that._error; reqGet.onsuccess = function (item) { complete(item); }; }); }); } } ); var IndexedDbDataSource = WinJS.Class.derive( WinJS.UI.VirtualizedDataSource, function (dbName, dbVersion, objectStoreName, upgrade, error) { this._adapter = new IndexedDbDataAdapter(dbName, dbVersion, objectStoreName, upgrade, error); this._baseDataSourceConstructor(this._adapter); }, { nuke: function () { this._adapter.nuke(); }, remove: function (key) { this._adapter.removeInternal(key); } } ); WinJS.Namespace.define("DataSources", { IndexedDbDataSource: IndexedDbDataSource }); })(); Summary In this blog post, I provided an overview of how you can create a new data source which you can use with the WinJS library. I described how you can create an IndexedDbDataSource which you can use to bind a ListView control to an IndexedDB database. While describing how you can create a custom data source, I explained how you can implement the IListDataAdapter interface. You also learned how to raise notifications — such as a removed or invalidateAll notification — by taking advantage of the methods of the IListDataNotificationHandler interface.

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  • Metro Walkthrough: Creating a Task List with a ListView and IndexedDB

    - by Stephen.Walther
    The goal of this blog entry is to describe how you can work with data in a Metro style application written with JavaScript. In particular, we create a super simple Task List application which enables you to create and delete tasks. Here’s a video which demonstrates how the Task List application works: In order to build this application, I had to take advantage of several features of the WinJS library and technologies including: IndexedDB – The Task List application stores data in an IndexedDB database. HTML5 Form Validation – The Task List application uses HTML5 validation to ensure that a required field has a value. ListView Control – The Task List application displays the tasks retrieved from the IndexedDB database in a WinJS ListView control. Creating the IndexedDB Database The Task List application stores all of its data in an IndexedDB database named TasksDB. This database is opened/created with the following code: var db; var req = window.msIndexedDB.open("TasksDB", 1); req.onerror = function () { console.log("Could not open database"); }; req.onupgradeneeded = function (evt) { var newDB = evt.target.result; newDB.createObjectStore("tasks", { keyPath: "id", autoIncrement:true }); }; The msIndexedDB.open() method accepts two parameters: the name of the database to open and the version of the database to open. If a database with a matching version already exists, then calling the msIndexedDB.open() method opens a connection to the existing database. If the database does not exist then the upgradeneeded event is raised. You handle the upgradeneeded event to create a new database. In the code above, the upgradeneeded event handler creates an object store named “tasks” (An object store roughly corresponds to a database table). When you add items to the tasks object store then each item gets an id property with an auto-incremented value automatically. The code above also includes an error event handler. If the IndexedDB database cannot be opened or created, for whatever reason, then an error message is written to the Visual Studio JavaScript Console window. Displaying a List of Tasks The TaskList application retrieves its list of tasks from the tasks object store, which we created above, and displays the list of tasks in a ListView control. Here is how the ListView control is declared: <div id="tasksListView" data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource: TaskList.tasks.dataSource, itemTemplate: select('#taskTemplate'), tapBehavior: 'toggleSelect', selectionMode: 'multi', layout: { type: WinJS.UI.ListLayout } }"> </div> The ListView control is bound to the TaskList.tasks.dataSource data source. The TaskList.tasks.dataSource is created with the following code: // Create the data source var tasks = new WinJS.Binding.List(); // Open the database var db; var req = window.msIndexedDB.open("TasksDB", 1); req.onerror = function () { console.log("Could not open database"); }; req.onupgradeneeded = function (evt) { var newDB = evt.target.result; newDB.createObjectStore("tasks", { keyPath: "id", autoIncrement:true }); }; // Load the data source with data from the database req.onsuccess = function () { db = req.result; var tran = db.transaction("tasks"); tran.objectStore("tasks").openCursor().onsuccess = function(event) { var cursor = event.target.result; if (cursor) { tasks.dataSource.insertAtEnd(null, cursor.value); cursor.continue(); }; }; }; // Expose the data source and functions WinJS.Namespace.define("TaskList", { tasks: tasks }); Notice the success event handler. This handler is called when a database is successfully opened/created. In the code above, all of the items from the tasks object store are retrieved into a cursor and added to a WinJS.Binding.List object named tasks. Because the ListView control is bound to the WinJS.Binding.List object, copying the tasks from the object store into the WinJS.Binding.List object causes the tasks to appear in the ListView: Adding a New Task You add a new task in the Task List application by entering the title of a new task into an HTML form and clicking the Add button. Here’s the markup for creating the form: <form id="addTaskForm"> <input id="newTaskTitle" title="New Task" required /> <button>Add</button> </form> Notice that the INPUT element includes a required attribute. In a Metro application, you can take advantage of HTML5 Validation to validate form fields. If you don’t enter a value for the newTaskTitle field then the following validation error message is displayed: For a brief introduction to HTML5 validation, see my previous blog entry: http://stephenwalther.com/blog/archive/2012/03/13/html5-form-validation.aspx When you click the Add button, the form is submitted and the form submit event is raised. The following code is executed in the default.js file: // Handle Add Task document.getElementById("addTaskForm").addEventListener("submit", function (evt) { evt.preventDefault(); var newTaskTitle = document.getElementById("newTaskTitle"); TaskList.addTask({ title: newTaskTitle.value }); newTaskTitle.value = ""; }); The code above retrieves the title of the new task and calls the addTask() method in the tasks.js file. Here’s the code for the addTask() method which is responsible for actually adding the new task to the IndexedDB database: // Add a new task function addTask(taskToAdd) { var transaction = db.transaction("tasks", "readwrite"); var addRequest = transaction.objectStore("tasks").add(taskToAdd); addRequest.onsuccess = function (evt) { taskToAdd.id = evt.target.result; tasks.dataSource.insertAtEnd(null, taskToAdd); } } The code above does two things. First, it adds the new task to the tasks object store in the IndexedDB database. Second, it adds the new task to the data source bound to the ListView. The dataSource.insertAtEnd() method is called to add the new task to the data source so the new task will appear in the ListView (with a nice little animation). Deleting Existing Tasks The Task List application enables you to select one or more tasks by clicking or tapping on one or more tasks in the ListView. When you click the Delete button, the selected tasks are removed from both the IndexedDB database and the ListView. For example, in the following screenshot, two tasks are selected. The selected tasks appear with a teal background and a checkmark: When you click the Delete button, the following code in the default.js file is executed: // Handle Delete Tasks document.getElementById("btnDeleteTasks").addEventListener("click", function (evt) { tasksListView.winControl.selection.getItems().then(function(items) { items.forEach(function (item) { TaskList.deleteTask(item); }); }); }); The selected tasks are retrieved with the TaskList selection.getItem() method. In the code above, the deleteTask() method is called for each of the selected tasks. Here’s the code for the deleteTask() method: // Delete an existing task function deleteTask(listViewItem) { // Database key != ListView key var dbKey = listViewItem.data.id; var listViewKey = listViewItem.key; // Remove item from db and, if success, remove item from ListView var transaction = db.transaction("tasks", “readwrite”); var deleteRequest = transaction.objectStore("tasks").delete(dbKey); deleteRequest.onsuccess = function () { tasks.dataSource.remove(listViewKey); } } This code does two things: it deletes the existing task from the database and removes the existing task from the ListView. In both cases, the right task is removed by using the key associated with the task. However, the task key is different in the case of the database and in the case of the ListView. In the case of the database, the task key is the value of the task id property. In the case of the ListView, on the other hand, the task key is auto-generated by the ListView. When the task is removed from the ListView, an animation is used to collapse the tasks which appear above and below the task which was removed. The Complete Code Above, I did a lot of jumping around between different files in the application and I left out sections of code. For the sake of completeness, I want to include the entire code here: the default.html, default.js, and tasks.js files. Here are the contents of the default.html file. This file contains the UI for the Task List application: <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Task List</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- TaskList references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> <script type="text/javascript" src="js/tasks.js"></script> <style type="text/css"> body { font-size: x-large; } form { display: inline; } #appContainer { margin: 20px; width: 600px; } .win-container { padding: 10px; } </style> </head> <body> <div> <!-- Templates --> <div id="taskTemplate" data-win-control="WinJS.Binding.Template"> <div> <span data-win-bind="innerText:title"></span> </div> </div> <h1>Super Task List</h1> <div id="appContainer"> <form id="addTaskForm"> <input id="newTaskTitle" title="New Task" required /> <button>Add</button> </form> <button id="btnDeleteTasks">Delete</button> <div id="tasksListView" data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource: TaskList.tasks.dataSource, itemTemplate: select('#taskTemplate'), tapBehavior: 'toggleSelect', selectionMode: 'multi', layout: { type: WinJS.UI.ListLayout } }"> </div> </div> </div> </body> </html> Here is the code for the default.js file. This code wires up the Add Task form and Delete button: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { WinJS.UI.processAll().then(function () { // Get reference to Tasks ListView var tasksListView = document.getElementById("tasksListView"); // Handle Add Task document.getElementById("addTaskForm").addEventListener("submit", function (evt) { evt.preventDefault(); var newTaskTitle = document.getElementById("newTaskTitle"); TaskList.addTask({ title: newTaskTitle.value }); newTaskTitle.value = ""; }); // Handle Delete Tasks document.getElementById("btnDeleteTasks").addEventListener("click", function (evt) { tasksListView.winControl.selection.getItems().then(function(items) { items.forEach(function (item) { TaskList.deleteTask(item); }); }); }); }); } }; app.start(); })(); Finally, here is the tasks.js file. This file contains all of the code for opening, creating, and interacting with IndexedDB: (function () { "use strict"; // Create the data source var tasks = new WinJS.Binding.List(); // Open the database var db; var req = window.msIndexedDB.open("TasksDB", 1); req.onerror = function () { console.log("Could not open database"); }; req.onupgradeneeded = function (evt) { var newDB = evt.target.result; newDB.createObjectStore("tasks", { keyPath: "id", autoIncrement:true }); }; // Load the data source with data from the database req.onsuccess = function () { db = req.result; var tran = db.transaction("tasks"); tran.objectStore("tasks").openCursor().onsuccess = function(event) { var cursor = event.target.result; if (cursor) { tasks.dataSource.insertAtEnd(null, cursor.value); cursor.continue(); }; }; }; // Add a new task function addTask(taskToAdd) { var transaction = db.transaction("tasks", "readwrite"); var addRequest = transaction.objectStore("tasks").add(taskToAdd); addRequest.onsuccess = function (evt) { taskToAdd.id = evt.target.result; tasks.dataSource.insertAtEnd(null, taskToAdd); } } // Delete an existing task function deleteTask(listViewItem) { // Database key != ListView key var dbKey = listViewItem.data.id; var listViewKey = listViewItem.key; // Remove item from db and, if success, remove item from ListView var transaction = db.transaction("tasks", "readwrite"); var deleteRequest = transaction.objectStore("tasks").delete(dbKey); deleteRequest.onsuccess = function () { tasks.dataSource.remove(listViewKey); } } // Expose the data source and functions WinJS.Namespace.define("TaskList", { tasks: tasks, addTask: addTask, deleteTask: deleteTask }); })(); Summary I wrote this blog entry because I wanted to create a walkthrough of building a simple database-driven application. In particular, I wanted to demonstrate how you can use a ListView control with an IndexedDB database to store and retrieve database data.

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  • Metro Walkthrough: Creating a Task List with a ListView and IndexedDB

    - by Stephen.Walther
    The goal of this blog entry is to describe how you can work with data in a Metro style application written with JavaScript. In particular, we create a super simple Task List application which enables you to create and delete tasks. Here’s a video which demonstrates how the Task List application works: In order to build this application, I had to take advantage of several features of the WinJS library and technologies including: IndexedDB – The Task List application stores data in an IndexedDB database. HTML5 Form Validation – The Task List application uses HTML5 validation to ensure that a required field has a value. ListView Control – The Task List application displays the tasks retrieved from the IndexedDB database in a WinJS ListView control. Creating the IndexedDB Database The Task List application stores all of its data in an IndexedDB database named TasksDB. This database is opened/created with the following code: var db; var req = window.msIndexedDB.open("TasksDB", 1); req.onerror = function () { console.log("Could not open database"); }; req.onupgradeneeded = function (evt) { var newDB = evt.target.result; newDB.createObjectStore("tasks", { keyPath: "id", autoIncrement:true }); }; The msIndexedDB.open() method accepts two parameters: the name of the database to open and the version of the database to open. If a database with a matching version already exists, then calling the msIndexedDB.open() method opens a connection to the existing database. If the database does not exist then the upgradeneeded event is raised. You handle the upgradeneeded event to create a new database. In the code above, the upgradeneeded event handler creates an object store named “tasks” (An object store roughly corresponds to a database table). When you add items to the tasks object store then each item gets an id property with an auto-incremented value automatically. The code above also includes an error event handler. If the IndexedDB database cannot be opened or created, for whatever reason, then an error message is written to the Visual Studio JavaScript Console window. Displaying a List of Tasks The TaskList application retrieves its list of tasks from the tasks object store, which we created above, and displays the list of tasks in a ListView control. Here is how the ListView control is declared: <div id="tasksListView" data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource: TaskList.tasks.dataSource, itemTemplate: select('#taskTemplate'), tapBehavior: 'toggleSelect', selectionMode: 'multi', layout: { type: WinJS.UI.ListLayout } }"> </div> The ListView control is bound to the TaskList.tasks.dataSource data source. The TaskList.tasks.dataSource is created with the following code: // Create the data source var tasks = new WinJS.Binding.List(); // Open the database var db; var req = window.msIndexedDB.open("TasksDB", 1); req.onerror = function () { console.log("Could not open database"); }; req.onupgradeneeded = function (evt) { var newDB = evt.target.result; newDB.createObjectStore("tasks", { keyPath: "id", autoIncrement:true }); }; // Load the data source with data from the database req.onsuccess = function () { db = req.result; var tran = db.transaction("tasks"); tran.objectStore("tasks").openCursor().onsuccess = function(event) { var cursor = event.target.result; tasks.dataSource.beginEdits(); if (cursor) { tasks.dataSource.insertAtEnd(null, cursor.value); cursor.continue(); } else { tasks.dataSource.endEdits(); }; }; }; // Expose the data source and functions WinJS.Namespace.define("TaskList", { tasks: tasks }); Notice the success event handler. This handler is called when a database is successfully opened/created. In the code above, all of the items from the tasks object store are retrieved into a cursor and added to a WinJS.Binding.List object named tasks. Because the ListView control is bound to the WinJS.Binding.List object, copying the tasks from the object store into the WinJS.Binding.List object causes the tasks to appear in the ListView: Adding a New Task You add a new task in the Task List application by entering the title of a new task into an HTML form and clicking the Add button. Here’s the markup for creating the form: <form id="addTaskForm"> <input id="newTaskTitle" title="New Task" required /> <button>Add</button> </form> Notice that the INPUT element includes a required attribute. In a Metro application, you can take advantage of HTML5 Validation to validate form fields. If you don’t enter a value for the newTaskTitle field then the following validation error message is displayed: For a brief introduction to HTML5 validation, see my previous blog entry: http://stephenwalther.com/blog/archive/2012/03/13/html5-form-validation.aspx When you click the Add button, the form is submitted and the form submit event is raised. The following code is executed in the default.js file: // Handle Add Task document.getElementById("addTaskForm").addEventListener("submit", function (evt) { evt.preventDefault(); var newTaskTitle = document.getElementById("newTaskTitle"); TaskList.addTask({ title: newTaskTitle.value }); newTaskTitle.value = ""; }); The code above retrieves the title of the new task and calls the addTask() method in the tasks.js file. Here’s the code for the addTask() method which is responsible for actually adding the new task to the IndexedDB database: // Add a new task function addTask(taskToAdd) { var transaction = db.transaction("tasks", IDBTransaction.READ_WRITE); var addRequest = transaction.objectStore("tasks").add(taskToAdd); addRequest.onsuccess = function (evt) { taskToAdd.id = evt.target.result; tasks.dataSource.insertAtEnd(null, taskToAdd); } } The code above does two things. First, it adds the new task to the tasks object store in the IndexedDB database. Second, it adds the new task to the data source bound to the ListView. The dataSource.insertAtEnd() method is called to add the new task to the data source so the new task will appear in the ListView (with a nice little animation). Deleting Existing Tasks The Task List application enables you to select one or more tasks by clicking or tapping on one or more tasks in the ListView. When you click the Delete button, the selected tasks are removed from both the IndexedDB database and the ListView. For example, in the following screenshot, two tasks are selected. The selected tasks appear with a teal background and a checkmark: When you click the Delete button, the following code in the default.js file is executed: // Handle Delete Tasks document.getElementById("btnDeleteTasks").addEventListener("click", function (evt) { tasksListView.winControl.selection.getItems().then(function(items) { items.forEach(function (item) { TaskList.deleteTask(item); }); }); }); The selected tasks are retrieved with the TaskList selection.getItem() method. In the code above, the deleteTask() method is called for each of the selected tasks. Here’s the code for the deleteTask() method: // Delete an existing task function deleteTask(listViewItem) { // Database key != ListView key var dbKey = listViewItem.data.id; var listViewKey = listViewItem.key; // Remove item from db and, if success, remove item from ListView var transaction = db.transaction("tasks", IDBTransaction.READ_WRITE); var deleteRequest = transaction.objectStore("tasks").delete(dbKey); deleteRequest.onsuccess = function () { tasks.dataSource.remove(listViewKey); } } This code does two things: it deletes the existing task from the database and removes the existing task from the ListView. In both cases, the right task is removed by using the key associated with the task. However, the task key is different in the case of the database and in the case of the ListView. In the case of the database, the task key is the value of the task id property. In the case of the ListView, on the other hand, the task key is auto-generated by the ListView. When the task is removed from the ListView, an animation is used to collapse the tasks which appear above and below the task which was removed. The Complete Code Above, I did a lot of jumping around between different files in the application and I left out sections of code. For the sake of completeness, I want to include the entire code here: the default.html, default.js, and tasks.js files. Here are the contents of the default.html file. This file contains the UI for the Task List application: <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Task List</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- TaskList references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> <script type="text/javascript" src="js/tasks.js"></script> <style type="text/css"> body { font-size: x-large; } form { display: inline; } #appContainer { margin: 20px; width: 600px; } .win-container { padding: 10px; } </style> </head> <body> <div> <!-- Templates --> <div id="taskTemplate" data-win-control="WinJS.Binding.Template"> <div> <span data-win-bind="innerText:title"></span> </div> </div> <h1>Super Task List</h1> <div id="appContainer"> <form id="addTaskForm"> <input id="newTaskTitle" title="New Task" required /> <button>Add</button> </form> <button id="btnDeleteTasks">Delete</button> <div id="tasksListView" data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource: TaskList.tasks.dataSource, itemTemplate: select('#taskTemplate'), tapBehavior: 'toggleSelect', selectionMode: 'multi', layout: { type: WinJS.UI.ListLayout } }"> </div> </div> </div> </body> </html> Here is the code for the default.js file. This code wires up the Add Task form and Delete button: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { WinJS.UI.processAll().then(function () { // Get reference to Tasks ListView var tasksListView = document.getElementById("tasksListView"); // Handle Add Task document.getElementById("addTaskForm").addEventListener("submit", function (evt) { evt.preventDefault(); var newTaskTitle = document.getElementById("newTaskTitle"); TaskList.addTask({ title: newTaskTitle.value }); newTaskTitle.value = ""; }); // Handle Delete Tasks document.getElementById("btnDeleteTasks").addEventListener("click", function (evt) { tasksListView.winControl.selection.getItems().then(function(items) { items.forEach(function (item) { TaskList.deleteTask(item); }); }); }); }); } }; app.start(); })(); Finally, here is the tasks.js file. This file contains all of the code for opening, creating, and interacting with IndexedDB: (function () { "use strict"; // Create the data source var tasks = new WinJS.Binding.List(); // Open the database var db; var req = window.msIndexedDB.open("TasksDB", 1); req.onerror = function () { console.log("Could not open database"); }; req.onupgradeneeded = function (evt) { var newDB = evt.target.result; newDB.createObjectStore("tasks", { keyPath: "id", autoIncrement:true }); }; // Load the data source with data from the database req.onsuccess = function () { db = req.result; var tran = db.transaction("tasks"); tran.objectStore("tasks").openCursor().onsuccess = function(event) { var cursor = event.target.result; tasks.dataSource.beginEdits(); if (cursor) { tasks.dataSource.insertAtEnd(null, cursor.value); cursor.continue(); } else { tasks.dataSource.endEdits(); }; }; }; // Add a new task function addTask(taskToAdd) { var transaction = db.transaction("tasks", IDBTransaction.READ_WRITE); var addRequest = transaction.objectStore("tasks").add(taskToAdd); addRequest.onsuccess = function (evt) { taskToAdd.id = evt.target.result; tasks.dataSource.insertAtEnd(null, taskToAdd); } } // Delete an existing task function deleteTask(listViewItem) { // Database key != ListView key var dbKey = listViewItem.data.id; var listViewKey = listViewItem.key; // Remove item from db and, if success, remove item from ListView var transaction = db.transaction("tasks", IDBTransaction.READ_WRITE); var deleteRequest = transaction.objectStore("tasks").delete(dbKey); deleteRequest.onsuccess = function () { tasks.dataSource.remove(listViewKey); } } // Expose the data source and functions WinJS.Namespace.define("TaskList", { tasks: tasks, addTask: addTask, deleteTask: deleteTask }); })(); Summary I wrote this blog entry because I wanted to create a walkthrough of building a simple database-driven application. In particular, I wanted to demonstrate how you can use a ListView control with an IndexedDB database to store and retrieve database data.

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  • Metro: Namespaces and Modules

    - by Stephen.Walther
    The goal of this blog entry is to describe how you can use the Windows JavaScript (WinJS) library to create namespaces. In particular, you learn how to use the WinJS.Namespace.define() and WinJS.Namespace.defineWithParent() methods. You also learn how to hide private methods by using the module pattern. Why Do We Need Namespaces? Before we do anything else, we should start by answering the question: Why do we need namespaces? What function do they serve? Do they just add needless complexity to our Metro applications? After all, plenty of JavaScript libraries do just fine without introducing support for namespaces. For example, jQuery has no support for namespaces and jQuery is the most popular JavaScript library in the universe. If jQuery can do without namespaces, why do we need to worry about namespaces at all? Namespaces perform two functions in a programming language. First, namespaces prevent naming collisions. In other words, namespaces enable you to create more than one object with the same name without conflict. For example, imagine that two companies – company A and company B – both want to make a JavaScript shopping cart control and both companies want to name the control ShoppingCart. By creating a CompanyA namespace and CompanyB namespace, both companies can create a ShoppingCart control: a CompanyA.ShoppingCart and a CompanyB.ShoppingCart control. The second function of a namespace is organization. Namespaces are used to group related functionality even when the functionality is defined in different physical files. For example, I know that all of the methods in the WinJS library related to working with classes can be found in the WinJS.Class namespace. Namespaces make it easier to understand the functionality available in a library. If you are building a simple JavaScript application then you won’t have much reason to care about namespaces. If you need to use multiple libraries written by different people then namespaces become very important. Using WinJS.Namespace.define() In the WinJS library, the most basic method of creating a namespace is to use the WinJS.Namespace.define() method. This method enables you to declare a namespace (of arbitrary depth). The WinJS.Namespace.define() method has the following parameters: · name – A string representing the name of the new namespace. You can add nested namespace by using dot notation · members – An optional collection of objects to add to the new namespace For example, the following code sample declares two new namespaces named CompanyA and CompanyB.Controls. Both namespaces contain a ShoppingCart object which has a checkout() method: // Create CompanyA namespace with ShoppingCart WinJS.Namespace.define("CompanyA"); CompanyA.ShoppingCart = { checkout: function (){ return "Checking out from A"; } }; // Create CompanyB.Controls namespace with ShoppingCart WinJS.Namespace.define( "CompanyB.Controls", { ShoppingCart: { checkout: function(){ return "Checking out from B"; } } } ); // Call CompanyA ShoppingCart checkout method console.log(CompanyA.ShoppingCart.checkout()); // Writes "Checking out from A" // Call CompanyB.Controls checkout method console.log(CompanyB.Controls.ShoppingCart.checkout()); // Writes "Checking out from B" In the code above, the CompanyA namespace is created by calling WinJS.Namespace.define(“CompanyA”). Next, the ShoppingCart is added to this namespace. The namespace is defined and an object is added to the namespace in separate lines of code. A different approach is taken in the case of the CompanyB.Controls namespace. The namespace is created and the ShoppingCart object is added to the namespace with the following single line of code: WinJS.Namespace.define( "CompanyB.Controls", { ShoppingCart: { checkout: function(){ return "Checking out from B"; } } } ); Notice that CompanyB.Controls is a nested namespace. The top level namespace CompanyB contains the namespace Controls. You can declare a nested namespace using dot notation and the WinJS library handles the details of creating one namespace within the other. After the namespaces have been defined, you can use either of the two shopping cart controls. You call CompanyA.ShoppingCart.checkout() or you can call CompanyB.Controls.ShoppingCart.checkout(). Using WinJS.Namespace.defineWithParent() The WinJS.Namespace.defineWithParent() method is similar to the WinJS.Namespace.define() method. Both methods enable you to define a new namespace. The difference is that the defineWithParent() method enables you to add a new namespace to an existing namespace. The WinJS.Namespace.defineWithParent() method has the following parameters: · parentNamespace – An object which represents a parent namespace · name – A string representing the new namespace to add to the parent namespace · members – An optional collection of objects to add to the new namespace The following code sample demonstrates how you can create a root namespace named CompanyA and add a Controls child namespace to the CompanyA parent namespace: WinJS.Namespace.define("CompanyA"); WinJS.Namespace.defineWithParent(CompanyA, "Controls", { ShoppingCart: { checkout: function () { return "Checking out"; } } } ); console.log(CompanyA.Controls.ShoppingCart.checkout()); // Writes "Checking out" One significant advantage of using the defineWithParent() method over the define() method is the defineWithParent() method is strongly-typed. In other words, you use an object to represent the base namespace instead of a string. If you misspell the name of the object (CompnyA) then you get a runtime error. Using the Module Pattern When you are building a JavaScript library, you want to be able to create both public and private methods. Some methods, the public methods, are intended to be used by consumers of your JavaScript library. The public methods act as your library’s public API. Other methods, the private methods, are not intended for public consumption. Instead, these methods are internal methods required to get the library to function. You don’t want people calling these internal methods because you might need to change them in the future. JavaScript does not support access modifiers. You can’t mark an object or method as public or private. Anyone gets to call any method and anyone gets to interact with any object. The only mechanism for encapsulating (hiding) methods and objects in JavaScript is to take advantage of functions. In JavaScript, a function determines variable scope. A JavaScript variable either has global scope – it is available everywhere – or it has function scope – it is available only within a function. If you want to hide an object or method then you need to place it within a function. For example, the following code contains a function named doSomething() which contains a nested function named doSomethingElse(): function doSomething() { console.log("doSomething"); function doSomethingElse() { console.log("doSomethingElse"); } } doSomething(); // Writes "doSomething" doSomethingElse(); // Throws ReferenceError You can call doSomethingElse() only within the doSomething() function. The doSomethingElse() function is encapsulated in the doSomething() function. The WinJS library takes advantage of function encapsulation to hide all of its internal methods. All of the WinJS methods are defined within self-executing anonymous functions. Everything is hidden by default. Public methods are exposed by explicitly adding the public methods to namespaces defined in the global scope. Imagine, for example, that I want a small library of utility methods. I want to create a method for calculating sales tax and a method for calculating the expected ship date of a product. The following library encapsulates the implementation of my library in a self-executing anonymous function: (function (global) { // Public method which calculates tax function calculateTax(price) { return calculateFederalTax(price) + calculateStateTax(price); } // Private method for calculating state tax function calculateStateTax(price) { return price * 0.08; } // Private method for calculating federal tax function calculateFederalTax(price) { return price * 0.02; } // Public method which returns the expected ship date function calculateShipDate(currentDate) { currentDate.setDate(currentDate.getDate() + 4); return currentDate; } // Export public methods WinJS.Namespace.define("CompanyA.Utilities", { calculateTax: calculateTax, calculateShipDate: calculateShipDate } ); })(this); // Show expected ship date var shipDate = CompanyA.Utilities.calculateShipDate(new Date()); console.log(shipDate); // Show price + tax var price = 12.33; var tax = CompanyA.Utilities.calculateTax(price); console.log(price + tax); In the code above, the self-executing anonymous function contains four functions: calculateTax(), calculateStateTax(), calculateFederalTax(), and calculateShipDate(). The following statement is used to expose only the calcuateTax() and the calculateShipDate() functions: // Export public methods WinJS.Namespace.define("CompanyA.Utilities", { calculateTax: calculateTax, calculateShipDate: calculateShipDate } ); Because the calculateTax() and calcuateShipDate() functions are added to the CompanyA.Utilities namespace, you can call these two methods outside of the self-executing function. These are the public methods of your library which form the public API. The calculateStateTax() and calculateFederalTax() methods, on the other hand, are forever hidden within the black hole of the self-executing function. These methods are encapsulated and can never be called outside of scope of the self-executing function. These are the internal methods of your library. Summary The goal of this blog entry was to describe why and how you use namespaces with the WinJS library. You learned how to define namespaces using both the WinJS.Namespace.define() and WinJS.Namespace.defineWithParent() methods. We also discussed how to hide private members and expose public members using the module pattern.

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  • Metro: Promises

    - by Stephen.Walther
    The goal of this blog entry is to describe the Promise class in the WinJS library. You can use promises whenever you need to perform an asynchronous operation such as retrieving data from a remote website or a file from the file system. Promises are used extensively in the WinJS library. Asynchronous Programming Some code executes immediately, some code requires time to complete or might never complete at all. For example, retrieving the value of a local variable is an immediate operation. Retrieving data from a remote website takes longer or might not complete at all. When an operation might take a long time to complete, you should write your code so that it executes asynchronously. Instead of waiting for an operation to complete, you should start the operation and then do something else until you receive a signal that the operation is complete. An analogy. Some telephone customer service lines require you to wait on hold – listening to really bad music – until a customer service representative is available. This is synchronous programming and very wasteful of your time. Some newer customer service lines enable you to enter your telephone number so the customer service representative can call you back when a customer representative becomes available. This approach is much less wasteful of your time because you can do useful things while waiting for the callback. There are several patterns that you can use to write code which executes asynchronously. The most popular pattern in JavaScript is the callback pattern. When you call a function which might take a long time to return a result, you pass a callback function to the function. For example, the following code (which uses jQuery) includes a function named getFlickrPhotos which returns photos from the Flickr website which match a set of tags (such as “dog” and “funny”): function getFlickrPhotos(tags, callback) { $.getJSON( "http://api.flickr.com/services/feeds/photos_public.gne?jsoncallback=?", { tags: tags, tagmode: "all", format: "json" }, function (data) { if (callback) { callback(data.items); } } ); } getFlickrPhotos("funny, dogs", function(data) { $.each(data, function(index, item) { console.log(item); }); }); The getFlickr() function includes a callback parameter. When you call the getFlickr() function, you pass a function to the callback parameter which gets executed when the getFlicker() function finishes retrieving the list of photos from the Flickr web service. In the code above, the callback function simply iterates through the results and writes each result to the console. Using callbacks is a natural way to perform asynchronous programming with JavaScript. Instead of waiting for an operation to complete, sitting there and listening to really bad music, you can get a callback when the operation is complete. Using Promises The CommonJS website defines a promise like this (http://wiki.commonjs.org/wiki/Promises): “Promises provide a well-defined interface for interacting with an object that represents the result of an action that is performed asynchronously, and may or may not be finished at any given point in time. By utilizing a standard interface, different components can return promises for asynchronous actions and consumers can utilize the promises in a predictable manner.” A promise provides a standard pattern for specifying callbacks. In the WinJS library, when you create a promise, you can specify three callbacks: a complete callback, a failure callback, and a progress callback. Promises are used extensively in the WinJS library. The methods in the animation library, the control library, and the binding library all use promises. For example, the xhr() method included in the WinJS base library returns a promise. The xhr() method wraps calls to the standard XmlHttpRequest object in a promise. The following code illustrates how you can use the xhr() method to perform an Ajax request which retrieves a file named Photos.txt: var options = { url: "/data/photos.txt" }; WinJS.xhr(options).then( function (xmlHttpRequest) { console.log("success"); var data = JSON.parse(xmlHttpRequest.responseText); console.log(data); }, function(xmlHttpRequest) { console.log("fail"); }, function(xmlHttpRequest) { console.log("progress"); } ) The WinJS.xhr() method returns a promise. The Promise class includes a then() method which accepts three callback functions: a complete callback, an error callback, and a progress callback: Promise.then(completeCallback, errorCallback, progressCallback) In the code above, three anonymous functions are passed to the then() method. The three callbacks simply write a message to the JavaScript Console. The complete callback also dumps all of the data retrieved from the photos.txt file. Creating Promises You can create your own promises by creating a new instance of the Promise class. The constructor for the Promise class requires a function which accepts three parameters: a complete, error, and progress function parameter. For example, the code below illustrates how you can create a method named wait10Seconds() which returns a promise. The progress function is called every second and the complete function is not called until 10 seconds have passed: (function () { "use strict"; var app = WinJS.Application; function wait10Seconds() { return new WinJS.Promise(function (complete, error, progress) { var seconds = 0; var intervalId = window.setInterval(function () { seconds++; progress(seconds); if (seconds > 9) { window.clearInterval(intervalId); complete(); } }, 1000); }); } app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { wait10Seconds().then( function () { console.log("complete") }, function () { console.log("error") }, function (seconds) { console.log("progress:" + seconds) } ); } } app.start(); })(); All of the work happens in the constructor function for the promise. The window.setInterval() method is used to execute code every second. Every second, the progress() callback method is called. If more than 10 seconds have passed then the complete() callback method is called and the clearInterval() method is called. When you execute the code above, you can see the output in the Visual Studio JavaScript Console. Creating a Timeout Promise In the previous section, we created a custom Promise which uses the window.setInterval() method to complete the promise after 10 seconds. We really did not need to create a custom promise because the Promise class already includes a static method for returning promises which complete after a certain interval. The code below illustrates how you can use the timeout() method. The timeout() method returns a promise which completes after a certain number of milliseconds. WinJS.Promise.timeout(3000).then( function(){console.log("complete")}, function(){console.log("error")}, function(){console.log("progress")} ); In the code above, the Promise completes after 3 seconds (3000 milliseconds). The Promise returned by the timeout() method does not support progress events. Therefore, the only message written to the console is the message “complete” after 10 seconds. Canceling Promises Some promises, but not all, support cancellation. When you cancel a promise, the promise’s error callback is executed. For example, the following code uses the WinJS.xhr() method to perform an Ajax request. However, immediately after the Ajax request is made, the request is cancelled. // Specify Ajax request options var options = { url: "/data/photos.txt" }; // Make the Ajax request var request = WinJS.xhr(options).then( function (xmlHttpRequest) { console.log("success"); }, function (xmlHttpRequest) { console.log("fail"); }, function (xmlHttpRequest) { console.log("progress"); } ); // Cancel the Ajax request request.cancel(); When you run the code above, the message “fail” is written to the Visual Studio JavaScript Console. Composing Promises You can build promises out of other promises. In other words, you can compose promises. There are two static methods of the Promise class which you can use to compose promises: the join() method and the any() method. When you join promises, a promise is complete when all of the joined promises are complete. When you use the any() method, a promise is complete when any of the promises complete. The following code illustrates how to use the join() method. A new promise is created out of two timeout promises. The new promise does not complete until both of the timeout promises complete: WinJS.Promise.join([WinJS.Promise.timeout(1000), WinJS.Promise.timeout(5000)]) .then(function () { console.log("complete"); }); The message “complete” will not be written to the JavaScript Console until both promises passed to the join() method completes. The message won’t be written for 5 seconds (5,000 milliseconds). The any() method completes when any promise passed to the any() method completes: WinJS.Promise.any([WinJS.Promise.timeout(1000), WinJS.Promise.timeout(5000)]) .then(function () { console.log("complete"); }); The code above writes the message “complete” to the JavaScript Console after 1 second (1,000 milliseconds). The message is written to the JavaScript console immediately after the first promise completes and before the second promise completes. Summary The goal of this blog entry was to describe WinJS promises. First, we discussed how promises enable you to easily write code which performs asynchronous actions. You learned how to use a promise when performing an Ajax request. Next, we discussed how you can create your own promises. You learned how to create a new promise by creating a constructor function with complete, error, and progress parameters. Finally, you learned about several advanced methods of promises. You learned how to use the timeout() method to create promises which complete after an interval of time. You also learned how to cancel promises and compose promises from other promises.

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  • Metro: Creating a Master/Detail View with a WinJS ListView Control

    - by Stephen.Walther
    The goal of this blog entry is to explain how you can create a simple master/detail view by using the WinJS ListView and Template controls. In particular, I explain how you can use a ListView control to display a list of movies and how you can use a Template control to display the details of the selected movie. Creating a master/detail view requires completing the following four steps: Create the data source – The data source contains the list of movies. Declare the ListView control – The ListView control displays the entire list of movies. It is the master part of the master/detail view. Declare the Details Template control – The Details Template control displays the details for the selected movie. It is the details part of the master/detail view. Handle the selectionchanged event – You handle the selectionchanged event to display the details for a movie when a new movie is selected. Creating the Data Source There is nothing special about our data source. We initialize a WinJS.Binding.List object to represent a list of movies: (function () { "use strict"; var movies = new WinJS.Binding.List([ { title: "Star Wars", director: "Lucas"}, { title: "Shrek", director: "Adamson" }, { title: "Star Trek", director: "Abrams" }, { title: "Spiderman", director: "Raimi" }, { title: "Memento", director: "Nolan" }, { title: "Minority Report", director: "Spielberg" } ]); // Expose the data source WinJS.Namespace.define("ListViewDemos", { movies: movies }); })(); The data source is exposed to the rest of our application with the name ListViewDemos.movies. Declaring the ListView Control The ListView control is declared with the following markup: <div id="movieList" data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource: ListViewDemos.movies.dataSource, itemTemplate: select('#masterItemTemplate'), tapBehavior: 'directSelect', selectionMode: 'single', layout: { type: WinJS.UI.ListLayout } }"> </div> The data-win-options attribute is used to set the following properties of the ListView control: itemDataSource – The ListView is bound to the list of movies which we created in the previous section. Notice that the ListView is bound to ListViewDemos.movies.dataSource and not just ListViewDemos.movies. itemTemplate – The item template contains the template used for rendering each item in the ListView. The markup for this template is included below. tabBehavior – This enumeration determines what happens when you tap or click on an item in the ListView. The possible values are directSelect, toggleSelect, invokeOnly, none. Because we want to handle the selectionchanged event, we set tapBehavior to the value directSelect. selectionMode – This enumeration determines whether you can select multiple items or only a single item. The possible values are none, single, multi. In the code above, this property is set to the value single. layout – You can use ListLayout or GridLayout with a ListView. If you want to display a vertical ListView, then you should select ListLayout. You must associate a ListView with an item template if you want to render anything interesting. The ListView above is associated with an item template named #masterItemTemplate. Here’s the markup for the masterItemTemplate: <div id="masterItemTemplate" data-win-control="WinJS.Binding.Template"> <div class="movie"> <span data-win-bind="innerText:title"></span> </div> </div> This template simply renders the title of each movie. Declaring the Details Template Control The details part of the master/detail view is created with the help of a Template control. Here’s the markup used to declare the Details Template control: <div id="detailsTemplate" data-win-control="WinJS.Binding.Template"> <div> <div> Title: <span data-win-bind="innerText:title"></span> </div> <div> Director: <span data-win-bind="innerText:director"></span> </div> </div> </div> The Details Template control displays the movie title and director.   Handling the selectionchanged Event The ListView control can raise two types of events: the iteminvoked and selectionchanged events. The iteminvoked event is raised when you click on a ListView item. The selectionchanged event is raised when one or more ListView items are selected. When you set the tapBehavior property of the ListView control to the value “directSelect” then tapping or clicking a list item raised both the iteminvoked and selectionchanged event. Tapping a list item causes the item to be selected and the item appears with a checkmark. In our code, we handle the selectionchanged event to update the movie details Template when you select a new movie. Here’s the code from the default.js file used to handle the selectionchanged event: var movieList = document.getElementById("movieList"); var detailsTemplate = document.getElementById("detailsTemplate"); var movieDetails = document.getElementById("movieDetails"); // Setup selectionchanged handler movieList.winControl.addEventListener("selectionchanged", function (evt) { if (movieList.winControl.selection.count() > 0) { movieList.winControl.selection.getItems().then(function (items) { // Clear the template container movieDetails.innerHTML = ""; // Render the template detailsTemplate.winControl.render(items[0].data, movieDetails); }); } }); The code above sets up an event handler (listener) for the selectionchanged event. The event handler first verifies that an item has been selected in the ListView (selection.count() > 0). Next, the details for the movie are rendered using the movie details Template (we created this Template in the previous section). The Complete Code For the sake of completeness, I’ve included the complete code for the master/detail view below. I’ve included both the default.html, default.js, and movies.js files. Here is the final code for the default.html file: <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>ListViewMasterDetail</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- ListViewMasterDetail references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> <script type="text/javascript" src="js/movies.js"></script> <style type="text/css"> body { font-size: xx-large; } .movie { padding: 5px; } #masterDetail { display: -ms-box; } #movieList { width: 300px; margin: 20px; } #movieDetails { margin: 20px; } </style> </head> <body> <!-- Templates --> <div id="masterItemTemplate" data-win-control="WinJS.Binding.Template"> <div class="movie"> <span data-win-bind="innerText:title"></span> </div> </div> <div id="detailsTemplate" data-win-control="WinJS.Binding.Template"> <div> <div> Title: <span data-win-bind="innerText:title"></span> </div> <div> Director: <span data-win-bind="innerText:director"></span> </div> </div> </div> <!-- Master/Detail --> <div id="masterDetail"> <!-- Master --> <div id="movieList" data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource: ListViewDemos.movies.dataSource, itemTemplate: select('#masterItemTemplate'), tapBehavior: 'directSelect', selectionMode: 'single', layout: { type: WinJS.UI.ListLayout } }"> </div> <!-- Detail --> <div id="movieDetails"></div> </div> </body> </html> Here is the default.js file: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { WinJS.UI.processAll(); var movieList = document.getElementById("movieList"); var detailsTemplate = document.getElementById("detailsTemplate"); var movieDetails = document.getElementById("movieDetails"); // Setup selectionchanged handler movieList.winControl.addEventListener("selectionchanged", function (evt) { if (movieList.winControl.selection.count() > 0) { movieList.winControl.selection.getItems().then(function (items) { // Clear the template container movieDetails.innerHTML = ""; // Render the template detailsTemplate.winControl.render(items[0].data, movieDetails); }); } }); } }; app.start(); })();   Here is the movies.js file: (function () { "use strict"; var movies = new WinJS.Binding.List([ { title: "Star Wars", director: "Lucas"}, { title: "Shrek", director: "Adamson" }, { title: "Star Trek", director: "Abrams" }, { title: "Spiderman", director: "Raimi" }, { title: "Memento", director: "Nolan" }, { title: "Minority Report", director: "Spielberg" } ]); // Expose the data source WinJS.Namespace.define("ListViewDemos", { movies: movies }); })();   Summary The purpose of this blog entry was to describe how to create a simple master/detail view by taking advantage of the WinJS ListView control. We handled the selectionchanged event of the ListView control to display movie details when you select a movie in the ListView.

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  • Metro: Understanding Observables

    - by Stephen.Walther
    The goal of this blog entry is to describe how the Observer Pattern is implemented in the WinJS library. You learn how to create observable objects which trigger notifications automatically when their properties are changed. Observables enable you to keep your user interface and your application data in sync. For example, by taking advantage of observables, you can update your user interface automatically whenever the properties of a product change. Observables are the foundation of declarative binding in the WinJS library. The WinJS library is not the first JavaScript library to include support for observables. For example, both the KnockoutJS library and the Microsoft Ajax Library (now part of the Ajax Control Toolkit) support observables. Creating an Observable Imagine that I have created a product object like this: var product = { name: "Milk", description: "Something to drink", price: 12.33 }; Nothing very exciting about this product. It has three properties named name, description, and price. Now, imagine that I want to be notified automatically whenever any of these properties are changed. In that case, I can create an observable product from my product object like this: var observableProduct = WinJS.Binding.as(product); This line of code creates a new JavaScript object named observableProduct from the existing JavaScript object named product. This new object also has a name, description, and price property. However, unlike the properties of the original product object, the properties of the observable product object trigger notifications when the properties are changed. Each of the properties of the new observable product object has been changed into accessor properties which have both a getter and a setter. For example, the observable product price property looks something like this: price: { get: function () { return this.getProperty(“price”); } set: function (value) { this.setProperty(“price”, value); } } When you read the price property then the getProperty() method is called and when you set the price property then the setProperty() method is called. The getProperty() and setProperty() methods are methods of the observable product object. The observable product object supports the following methods and properties: · addProperty(name, value) – Adds a new property to an observable and notifies any listeners. · backingData – An object which represents the value of each property. · bind(name, action) – Enables you to execute a function when a property changes. · getProperty(name) – Returns the value of a property using the string name of the property. · notify(name, newValue, oldValue) – A private method which executes each function in the _listeners array. · removeProperty(name) – Removes a property and notifies any listeners. · setProperty(name, value) – Updates a property and notifies any listeners. · unbind(name, action) – Enables you to stop executing a function in response to a property change. · updateProperty(name, value) – Updates a property and notifies any listeners. So when you create an observable, you get a new object with the same properties as an existing object. However, when you modify the properties of an observable object, then you can notify any listeners of the observable that the value of a particular property has changed automatically. Imagine that you change the value of the price property like this: observableProduct.price = 2.99; In that case, the following sequence of events is triggered: 1. The price setter calls the setProperty(“price”, 2.99) method 2. The setProperty() method updates the value of the backingData.price property and calls the notify() method 3. The notify() method executes each function in the collection of listeners associated with the price property Creating Observable Listeners If you want to be notified when a property of an observable object is changed, then you need to register a listener. You register a listener by using the bind() method like this: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price observableProduct.price = 2.99; } }; app.start(); })(); In the code above, the bind() method is used to associate the price property with a function. When the price property is changed, the function logs the new value of the price property to the Visual Studio JavaScript console. The price property is associated with the function using the following line of code: // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); Coalescing Notifications If you make multiple changes to a property – one change immediately following another – then separate notifications won’t be sent. Instead, any listeners are notified only once. The notifications are coalesced into a single notification. For example, in the following code, the product price property is updated three times. However, only one message is written to the JavaScript console. Only the last value assigned to the price property is written to the JavaScript Console window: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price observableProduct.price = 3.99; observableProduct.price = 2.99; observableProduct.price = 1.99; Only the last value assigned to price, the value 1.99, appears in the console: If there is a time delay between changes to a property then changes result in different notifications. For example, the following code updates the price property every second: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Add 1 to price every second window.setInterval(function () { observableProduct.price += 1; }, 1000); In this case, separate notification messages are logged to the JavaScript Console window: If you need to prevent multiple notifications from being coalesced into one then you can take advantage of promises. I discussed WinJS promises in a previous blog entry: http://stephenwalther.com/blog/archive/2012/02/22/windows-web-applications-promises.aspx Because the updateProperty() method returns a promise, you can create different notifications for each change in a property by using the following code: // Change the price observableProduct.updateProperty("price", 3.99) .then(function () { observableProduct.updateProperty("price", 2.99) .then(function () { observableProduct.updateProperty("price", 1.99); }); }); In this case, even though the price is immediately changed from 3.99 to 2.99 to 1.99, separate notifications for each new value of the price property are sent. Bypassing Notifications Normally, if a property of an observable object has listeners and you change the property then the listeners are notified. However, there are certain situations in which you might want to bypass notification. In other words, you might need to change a property value silently without triggering any functions registered for notification. If you want to change a property without triggering notifications then you should change the property by using the backingData property. The following code illustrates how you can change the price property silently: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price silently observableProduct.backingData.price = 5.99; console.log(observableProduct.price); // Writes 5.99 The price is changed to the value 5.99 by changing the value of backingData.price. Because the observableProduct.price property is not set directly, any listeners associated with the price property are not notified. When you change the value of a property by using the backingData property, the change in the property happens synchronously. However, when you change the value of an observable property directly, the change is always made asynchronously. Summary The goal of this blog entry was to describe observables. In particular, we discussed how to create observables from existing JavaScript objects and bind functions to observable properties. You also learned how notifications are coalesced (and ways to prevent this coalescing). Finally, we discussed how you can use the backingData property to update an observable property without triggering notifications. In the next blog entry, we’ll see how observables are used with declarative binding to display the values of properties in an HTML document.

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  • Metro: Using Templates

    - by Stephen.Walther
    The goal of this blog post is to describe how templates work in the WinJS library. In particular, you learn how to use a template to display both a single item and an array of items. You also learn how to load a template from an external file. Why use Templates? Imagine that you want to display a list of products in a page. The following code is bad: var products = [ { name: "Tesla", price: 80000 }, { name: "VW Rabbit", price: 200 }, { name: "BMW", price: 60000 } ]; var productsHTML = ""; for (var i = 0; i < products.length; i++) { productsHTML += "<h1>Product Details</h1>" + "<div>Product Name: " + products[i].name + "</div>" + "<div>Product Price: " + products[i].price + "</div>"; } document.getElementById("productContainer").innerHTML = productsHTML; In the code above, an array of products is displayed by creating a for..next loop which loops through each element in the array. A string which represents a list of products is built through concatenation. The code above is a designer’s nightmare. You cannot modify the appearance of the list of products without modifying the JavaScript code. A much better approach is to use a template like this: <div id="productTemplate"> <h1>Product Details</h1> <div> Product Name: <span data-win-bind="innerText:name"></span> </div> <div> Product Price: <span data-win-bind="innerText:price"></span> </div> </div> A template is simply a fragment of HTML that contains placeholders. Instead of displaying a list of products by concatenating together a string, you can render a template for each product. Creating a Simple Template Let’s start by using a template to render a single product. The following HTML page contains a template and a placeholder for rendering the template: <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Application1</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- Application1 references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> </head> <body> <!-- Product Template --> <div id="productTemplate"> <h1>Product Details</h1> <div> Product Name: <span data-win-bind="innerText:name"></span> </div> <div> Product Price: <span data-win-bind="innerText:price"></span> </div> </div> <!-- Place where Product Template is Rendered --> <div id="productContainer"></div> </body> </html> In the page above, the template is defined in a DIV element with the id productTemplate. The contents of the productTemplate are not displayed when the page is opened in the browser. The contents of a template are automatically hidden when you convert the productTemplate into a template in your JavaScript code. Notice that the template uses data-win-bind attributes to display the product name and price properties. You can use both data-win-bind and data-win-bindsource attributes within a template. To learn more about these attributes, see my earlier blog post on WinJS data binding: http://stephenwalther.com/blog/archive/2012/02/26/windows-web-applications-declarative-data-binding.aspx The page above also includes a DIV element named productContainer. The rendered template is added to this element. Here’s the code for the default.js script which creates and renders the template: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { var product = { name: "Tesla", price: 80000 }; var productTemplate = new WinJS.Binding.Template(document.getElementById("productTemplate")); productTemplate.render(product, document.getElementById("productContainer")); } }; app.start(); })(); In the code above, a single product object is created with the following line of code: var product = { name: "Tesla", price: 80000 }; Next, the productTemplate element from the page is converted into an actual WinJS template with the following line of code: var productTemplate = new WinJS.Binding.Template(document.getElementById("productTemplate")); The template is rendered to the templateContainer element with the following line of code: productTemplate.render(product, document.getElementById("productContainer")); The result of this work is that the product details are displayed: Notice that you do not need to call WinJS.Binding.processAll(). The Template render() method takes care of the binding for you. Displaying an Array in a Template If you want to display an array of products using a template then you simply need to create a for..next loop and iterate through the array calling the Template render() method for each element. (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { var products = [ { name: "Tesla", price: 80000 }, { name: "VW Rabbit", price: 200 }, { name: "BMW", price: 60000 } ]; var productTemplate = new WinJS.Binding.Template(document.getElementById("productTemplate")); var productContainer = document.getElementById("productContainer"); var i, product; for (i = 0; i < products.length; i++) { product = products[i]; productTemplate.render(product, productContainer); } } }; app.start(); })(); After each product in the array is rendered with the template, the result is appended to the productContainer element. No changes need to be made to the HTML page discussed in the previous section to display an array of products instead of a single product. The same product template can be used in both scenarios. Rendering an HTML TABLE with a Template When using the WinJS library, you create a template by creating an HTML element in your page. One drawback to this approach of creating templates is that your templates are part of your HTML page. In order for your HTML page to validate, the HTML within your templates must also validate. This means, for example, that you cannot enclose a single HTML table row within a template. The following HTML is invalid because you cannot place a TR element directly within the body of an HTML document:   <!-- Product Template --> <tr> <td data-win-bind="innerText:name"></td> <td data-win-bind="innerText:price"></td> </tr> This template won’t validate because, in a valid HTML5 document, a TR element must appear within a THEAD or TBODY element. Instead, you must create the entire TABLE element in the template. The following HTML page illustrates how you can create a template which contains a TR element: <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Application1</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- Application1 references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> </head> <body> <!-- Product Template --> <div id="productTemplate"> <table> <tbody> <tr> <td data-win-bind="innerText:name"></td> <td data-win-bind="innerText:price"></td> </tr> </tbody> </table> </div> <!-- Place where Product Template is Rendered --> <table> <thead> <tr> <th>Name</th><th>Price</th> </tr> </thead> <tbody id="productContainer"> </tbody> </table> </body> </html>   In the HTML page above, the product template includes TABLE and TBODY elements: <!-- Product Template --> <div id="productTemplate"> <table> <tbody> <tr> <td data-win-bind="innerText:name"></td> <td data-win-bind="innerText:price"></td> </tr> </tbody> </table> </div> We discard these elements when we render the template. The only reason that we include the TABLE and THEAD elements in the template is to make the HTML page validate as valid HTML5 markup. Notice that the productContainer (the target of the template) in the page above is a TBODY element. We want to add the rows rendered by the template to the TBODY element in the page. The productTemplate is rendered in the default.js file: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { var products = [ { name: "Tesla", price: 80000 }, { name: "VW Rabbit", price: 200 }, { name: "BMW", price: 60000 } ]; var productTemplate = new WinJS.Binding.Template(document.getElementById("productTemplate")); var productContainer = document.getElementById("productContainer"); var i, product, row; for (i = 0; i < products.length; i++) { product = products[i]; productTemplate.render(product).then(function (result) { row = WinJS.Utilities.query("tr", result).get(0); productContainer.appendChild(row); }); } } }; app.start(); })(); When the product template is rendered, the TR element is extracted from the rendered template by using the WinJS.Utilities.query() method. Next, only the TR element is added to the productContainer: productTemplate.render(product).then(function (result) { row = WinJS.Utilities.query("tr", result).get(0); productContainer.appendChild(row); }); I discuss the WinJS.Utilities.query() method in depth in a previous blog entry: http://stephenwalther.com/blog/archive/2012/02/23/windows-web-applications-query-selectors.aspx When everything gets rendered, the products are displayed in an HTML table: You can see the actual HTML rendered by looking at the Visual Studio DOM Explorer window:   Loading an External Template Instead of embedding a template in an HTML page, you can place your template in an external HTML file. It makes sense to create a template in an external file when you need to use the same template in multiple pages. For example, you might need to use the same product template in multiple pages in your application. The following HTML page does not contain a template. It only contains a container that will act as a target for the rendered template: <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Application1</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- Application1 references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> </head> <body> <!-- Place where Product Template is Rendered --> <div id="productContainer"></div> </body> </html> The template is contained in a separate file located at the path /templates/productTemplate.html:   Here’s the contents of the productTemplate.html file: <!-- Product Template --> <div id="productTemplate"> <h1>Product Details</h1> <div> Product Name: <span data-win-bind="innerText:name"></span> </div> <div> Product Price: <span data-win-bind="innerText:price"></span> </div> </div> Notice that the template file only contains the template and not the standard opening and closing HTML elements. It is an HTML fragment. If you prefer, you can include all of the standard opening and closing HTML elements in your external template – these elements get stripped away automatically: <html> <head><title>product template</title></head> <body> <!-- Product Template --> <div id="productTemplate"> <h1>Product Details</h1> <div> Product Name: <span data-win-bind="innerText:name"></span> </div> <div> Product Price: <span data-win-bind="innerText:price"></span> </div> </div> </body> </html> Either approach – using a fragment or using a full HTML document  — works fine. Finally, the following default.js file loads the external template, renders the template for each product, and appends the result to the product container: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { var products = [ { name: "Tesla", price: 80000 }, { name: "VW Rabbit", price: 200 }, { name: "BMW", price: 60000 } ]; var productTemplate = new WinJS.Binding.Template(null, { href: "/templates/productTemplate.html" }); var productContainer = document.getElementById("productContainer"); var i, product, row; for (i = 0; i < products.length; i++) { product = products[i]; productTemplate.render(product, productContainer); } } }; app.start(); })(); The path to the external template is passed to the constructor for the Template class as one of the options: var productTemplate = new WinJS.Binding.Template(null, {href:"/templates/productTemplate.html"}); When a template is contained in a page then you use the first parameter of the WinJS.Binding.Template constructor to represent the template – instead of null, you pass the element which contains the template. When a template is located in an external file, you pass the href for the file as part of the second parameter for the WinJS.Binding.Template constructor. Summary The goal of this blog entry was to describe how you can use WinJS templates to render either a single item or an array of items to a page. We also explored two advanced topics. You learned how to render an HTML table by extracting the TR element from a template. You also learned how to place a template in an external file.

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  • Change the Default Number of Rows of Tiles on the Windows 8 UI (Metro) Screen

    - by Lori Kaufman
    By default, Windows 8 automatically sets the number of rows of tiles to fit your screen, depending on your monitor size and resolution. However, you can tell Windows 8 to display a certain number of rows of tiles at all times, despite the screen resolution. To do this, we will make a change to the registry. If you are not already on the Desktop, click the Desktop tile on the Start screen. NOTE: Before making changes to the registry, be sure you back it up. We also recommend creating a restore point you can use to restore your system if something goes wrong. HTG Explains: Why Do Hard Drives Show the Wrong Capacity in Windows? Java is Insecure and Awful, It’s Time to Disable It, and Here’s How What Are the Windows A: and B: Drives Used For?

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  • My app 'Howzzat Book–Windows 8 Metro App is in the store now

    - by nmarun
    I’m just so excited that my application Howzzat Book passed all certifications and is now in the Windows Store. Here’s the email from MIcrosoft that I received: “Your app is in the Windows Store! Congratulations! Howzzat Book, release 1 is now in the Windows Store. Use this link to your app’s listing in the Windows Store to let others know about your app.” Link for Howzzat Book Now, since they’ve just added it to the store, it might take some time to be available for download. So if you don’t find...(read more)

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  • Metro: Grouping Items in a ListView Control

    - by Stephen.Walther
    The purpose of this blog entry is to explain how you can group list items when displaying the items in a WinJS ListView control. In particular, you learn how to group a list of products by product category. Displaying a grouped list of items in a ListView control requires completing the following steps: Create a Grouped data source from a List data source Create a Grouped Header Template Declare the ListView control so it groups the list items Creating the Grouped Data Source Normally, you bind a ListView control to a WinJS.Binding.List object. If you want to render list items in groups, then you need to bind the ListView to a grouped data source instead. The following code – contained in a file named products.js — illustrates how you can create a standard WinJS.Binding.List object from a JavaScript array and then return a grouped data source from the WinJS.Binding.List object by calling its createGrouped() method: (function () { "use strict"; // Create List data source var products = new WinJS.Binding.List([ { name: "Milk", price: 2.44, category: "Beverages" }, { name: "Oranges", price: 1.99, category: "Fruit" }, { name: "Wine", price: 8.55, category: "Beverages" }, { name: "Apples", price: 2.44, category: "Fruit" }, { name: "Steak", price: 1.99, category: "Other" }, { name: "Eggs", price: 2.44, category: "Other" }, { name: "Mushrooms", price: 1.99, category: "Other" }, { name: "Yogurt", price: 2.44, category: "Other" }, { name: "Soup", price: 1.99, category: "Other" }, { name: "Cereal", price: 2.44, category: "Other" }, { name: "Pepsi", price: 1.99, category: "Beverages" } ]); // Create grouped data source var groupedProducts = products.createGrouped( function (dataItem) { return dataItem.category; }, function (dataItem) { return { title: dataItem.category }; }, function (group1, group2) { return group1.charCodeAt(0) - group2.charCodeAt(0); } ); // Expose the grouped data source WinJS.Namespace.define("ListViewDemos", { products: groupedProducts }); })(); Notice that the createGrouped() method requires three functions as arguments: groupKey – This function associates each list item with a group. The function accepts a data item and returns a key which represents a group. In the code above, we return the value of the category property for each product. groupData – This function returns the data item displayed by the group header template. For example, in the code above, the function returns a title for the group which is displayed in the group header template. groupSorter – This function determines the order in which the groups are displayed. The code above displays the groups in alphabetical order: Beverages, Fruit, Other. Creating the Group Header Template Whenever you create a ListView control, you need to create an item template which you use to control how each list item is rendered. When grouping items in a ListView control, you also need to create a group header template. The group header template is used to render the header for each group of list items. Here’s the markup for both the item template and the group header template: <div id="productTemplate" data-win-control="WinJS.Binding.Template"> <div class="product"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> </div> <div id="productGroupHeaderTemplate" data-win-control="WinJS.Binding.Template"> <div class="productGroupHeader"> <h1 data-win-bind="innerText: title"></h1> </div> </div> You should declare the two templates in the same file as you declare the ListView control – for example, the default.html file. Declaring the ListView Control The final step is to declare the ListView control. Here’s the required markup: <div data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource:ListViewDemos.products.dataSource, itemTemplate:select('#productTemplate'), groupDataSource:ListViewDemos.products.groups.dataSource, groupHeaderTemplate:select('#productGroupHeaderTemplate'), layout: {type: WinJS.UI.GridLayout} }"> </div> In the markup above, six properties of the ListView control are set when the control is declared. First the itemDataSource and itemTemplate are specified. Nothing new here. Next, the group data source and group header template are specified. Notice that the group data source is represented by the ListViewDemos.products.groups.dataSource property of the grouped data source. Finally, notice that the layout of the ListView is changed to Grid Layout. You are required to use Grid Layout (instead of the default List Layout) when displaying grouped items in a ListView. Here’s the entire contents of the default.html page: <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>ListViewDemos</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- ListViewDemos references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> <script src="/js/products.js" type="text/javascript"></script> <style type="text/css"> .product { width: 200px; height: 100px; border: white solid 1px; font-size: x-large; } </style> </head> <body> <div id="productTemplate" data-win-control="WinJS.Binding.Template"> <div class="product"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> </div> <div id="productGroupHeaderTemplate" data-win-control="WinJS.Binding.Template"> <div class="productGroupHeader"> <h1 data-win-bind="innerText: title"></h1> </div> </div> <div data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource:ListViewDemos.products.dataSource, itemTemplate:select('#productTemplate'), groupDataSource:ListViewDemos.products.groups.dataSource, groupHeaderTemplate:select('#productGroupHeaderTemplate'), layout: {type: WinJS.UI.GridLayout} }"> </div> </body> </html> Notice that the default.html page includes a reference to the products.js file: <script src=”/js/products.js” type=”text/javascript”></script> The default.html page also contains the declarations of the item template, group header template, and ListView control. Summary The goal of this blog entry was to explain how you can group items in a ListView control. You learned how to create a grouped data source, a group header template, and declare a ListView so that it groups its list items.

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  • Metro: Dynamically Switching Templates with a WinJS ListView

    - by Stephen.Walther
    Imagine that you want to display a list of products using the WinJS ListView control. Imagine, furthermore, that you want to use different templates to display different products. In particular, when a product is on sale, you want to display the product using a special “On Sale” template. In this blog entry, I explain how you can switch templates dynamically when displaying items with a ListView control. In other words, you learn how to use more than one template when displaying items with a ListView control. Creating the Data Source Let’s start by creating the data source for the ListView. Nothing special here – our data source is a list of products. Two of the products, Oranges and Apples, are on sale. (function () { "use strict"; var products = new WinJS.Binding.List([ { name: "Milk", price: 2.44 }, { name: "Oranges", price: 1.99, onSale: true }, { name: "Wine", price: 8.55 }, { name: "Apples", price: 2.44, onSale: true }, { name: "Steak", price: 1.99 }, { name: "Eggs", price: 2.44 }, { name: "Mushrooms", price: 1.99 }, { name: "Yogurt", price: 2.44 }, { name: "Soup", price: 1.99 }, { name: "Cereal", price: 2.44 }, { name: "Pepsi", price: 1.99 } ]); WinJS.Namespace.define("ListViewDemos", { products: products }); })(); The file above is saved with the name products.js and referenced by the default.html page described below. Declaring the Templates and ListView Control Next, we need to declare the ListView control and the two Template controls which we will use to display template items. The markup below appears in the default.html file: <!-- Templates --> <div id="productItemTemplate" data-win-control="WinJS.Binding.Template"> <div class="product"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> </div> <div id="productOnSaleTemplate" data-win-control="WinJS.Binding.Template"> <div class="product onSale"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> (On Sale!) </div> </div> <!-- ListView --> <div id="productsListView" data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource: ListViewDemos.products.dataSource, layout: { type: WinJS.UI.ListLayout } }"> </div> In the markup above, two Template controls are declared. The first template is used when rendering a normal product and the second template is used when rendering a product which is on sale. The second template, unlike the first template, includes the text “(On Sale!)”. The ListView control is bound to the data source which we created in the previous section. The ListView itemDataSource property is set to the value ListViewDemos.products.dataSource. Notice that we do not set the ListView itemTemplate property. We set this property in the default.js file. Switching Between Templates All of the magic happens in the default.js file. The default.js file contains the JavaScript code used to switch templates dynamically. Here’s the entire contents of the default.js file: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { WinJS.UI.processAll().then(function () { var productsListView = document.getElementById("productsListView"); productsListView.winControl.itemTemplate = itemTemplateFunction; });; } }; function itemTemplateFunction(itemPromise) { return itemPromise.then(function (item) { // Select either normal product template or on sale template var itemTemplate = document.getElementById("productItemTemplate"); if (item.data.onSale) { itemTemplate = document.getElementById("productOnSaleTemplate"); }; // Render selected template to DIV container var container = document.createElement("div"); itemTemplate.winControl.render(item.data, container); return container; }); } app.start(); })(); In the code above, a function is assigned to the ListView itemTemplate property with the following line of code: productsListView.winControl.itemTemplate = itemTemplateFunction;   The itemTemplateFunction returns a DOM element which is used for the template item. Depending on the value of the product onSale property, the DOM element is generated from either the productItemTemplate or the productOnSaleTemplate template. Using Binding Converters instead of Multiple Templates In the previous sections, I explained how you can use different templates to render normal products and on sale products. There is an alternative approach to displaying different markup for normal products and on sale products. Instead of creating two templates, you can create a single template which contains separate DIV elements for a normal product and an on sale product. The following default.html file contains a single item template and a ListView control bound to the template. <!-- Template --> <div id="productItemTemplate" data-win-control="WinJS.Binding.Template"> <div class="product" data-win-bind="style.display: onSale ListViewDemos.displayNormalProduct"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> <div class="product onSale" data-win-bind="style.display: onSale ListViewDemos.displayOnSaleProduct"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> (On Sale!) </div> </div> <!-- ListView --> <div id="productsListView" data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource: ListViewDemos.products.dataSource, itemTemplate: select('#productItemTemplate'), layout: { type: WinJS.UI.ListLayout } }"> </div> The first DIV element is used to render a normal product: <div class="product" data-win-bind="style.display: onSale ListViewDemos.displayNormalProduct"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> The second DIV element is used to render an “on sale” product: <div class="product onSale" data-win-bind="style.display: onSale ListViewDemos.displayOnSaleProduct"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> (On Sale!) </div> Notice that both templates include a data-win-bind attribute. These data-win-bind attributes are used to show the “normal” template when a product is not on sale and show the “on sale” template when a product is on sale. These attributes set the Cascading Style Sheet display attribute to either “none” or “block”. The data-win-bind attributes take advantage of binding converters. The binding converters are defined in the default.js file: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { WinJS.UI.processAll(); } }; WinJS.Namespace.define("ListViewDemos", { displayNormalProduct: WinJS.Binding.converter(function (onSale) { return onSale ? "none" : "block"; }), displayOnSaleProduct: WinJS.Binding.converter(function (onSale) { return onSale ? "block" : "none"; }) }); app.start(); })(); The ListViewDemos.displayNormalProduct binding converter converts the value true or false to the value “none” or “block”. The ListViewDemos.displayOnSaleProduct binding converter does the opposite; it converts the value true or false to the value “block” or “none” (Sadly, you cannot simply place a NOT operator before the onSale property in the binding expression – you need to create both converters). The end result is that you can display different markup depending on the value of the product onSale property. Either the contents of the first or second DIV element are displayed: Summary In this blog entry, I’ve explored two approaches to displaying different markup in a ListView depending on the value of a data item property. The bulk of this blog entry was devoted to explaining how you can assign a function to the ListView itemTemplate property which returns different templates. We created both a productItemTemplate and productOnSaleTemplate and displayed both templates with the same ListView control. We also discussed how you can create a single template and display different markup by using binding converters. The binding converters are used to set a DIV element’s display property to either “none” or “block”. We created a binding converter which displays normal products and a binding converter which displays “on sale” products.

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  • Metro: Creating a Master/Detail View with a WinJS ListView Control

    - by Stephen.Walther
    The goal of this blog entry is to explain how you can create a simple master/detail view by using the WinJS ListView and Template controls. In particular, I explain how you can use a ListView control to display a list of movies and how you can use a Template control to display the details of the selected movie. Creating a master/detail view requires completing the following four steps: Create the data source – The data source contains the list of movies. Declare the ListView control – The ListView control displays the entire list of movies. It is the master part of the master/detail view. Declare the Details Template control – The Details Template control displays the details for the selected movie. It is the details part of the master/detail view. Handle the selectionchanged event – You handle the selectionchanged event to display the details for a movie when a new movie is selected. Creating the Data Source There is nothing special about our data source. We initialize a WinJS.Binding.List object to represent a list of movies: (function () { "use strict"; var movies = new WinJS.Binding.List([ { title: "Star Wars", director: "Lucas"}, { title: "Shrek", director: "Adamson" }, { title: "Star Trek", director: "Abrams" }, { title: "Spiderman", director: "Raimi" }, { title: "Memento", director: "Nolan" }, { title: "Minority Report", director: "Spielberg" } ]); // Expose the data source WinJS.Namespace.define("ListViewDemos", { movies: movies }); })(); The data source is exposed to the rest of our application with the name ListViewDemos.movies. Declaring the ListView Control The ListView control is declared with the following markup: <div id="movieList" data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource: ListViewDemos.movies.dataSource, itemTemplate: select('#masterItemTemplate'), tapBehavior: 'directSelect', selectionMode: 'single', layout: { type: WinJS.UI.ListLayout } }"> </div> The data-win-options attribute is used to set the following properties of the ListView control: itemDataSource – The ListView is bound to the list of movies which we created in the previous section. Notice that the ListView is bound to ListViewDemos.movies.dataSource and not just ListViewDemos.movies. itemTemplate – The item template contains the template used for rendering each item in the ListView. The markup for this template is included below. tabBehavior – This enumeration determines what happens when you tap or click on an item in the ListView. The possible values are directSelect, toggleSelect, invokeOnly, none. Because we want to handle the selectionchanged event, we set tapBehavior to the value directSelect. selectionMode – This enumeration determines whether you can select multiple items or only a single item. The possible values are none, single, multi. In the code above, this property is set to the value single. layout – You can use ListLayout or GridLayout with a ListView. If you want to display a vertical ListView, then you should select ListLayout. You must associate a ListView with an item template if you want to render anything interesting. The ListView above is associated with an item template named #masterItemTemplate. Here’s the markup for the masterItemTemplate: <div id="masterItemTemplate" data-win-control="WinJS.Binding.Template"> <div class="movie"> <span data-win-bind="innerText:title"></span> </div> </div> This template simply renders the title of each movie. Declaring the Details Template Control The details part of the master/detail view is created with the help of a Template control. Here’s the markup used to declare the Details Template control: <div id="detailsTemplate" data-win-control="WinJS.Binding.Template"> <div> <div> Title: <span data-win-bind="innerText:title"></span> </div> <div> Director: <span data-win-bind="innerText:director"></span> </div> </div> </div> The Details Template control displays the movie title and director.   Handling the selectionchanged Event The ListView control can raise two types of events: the iteminvoked and selectionchanged events. The iteminvoked event is raised when you click on a ListView item. The selectionchanged event is raised when one or more ListView items are selected. When you set the tapBehavior property of the ListView control to the value “directSelect” then tapping or clicking a list item raised both the iteminvoked and selectionchanged event. Tapping a list item causes the item to be selected and the item appears with a checkmark. In our code, we handle the selectionchanged event to update the movie details Template when you select a new movie. Here’s the code from the default.js file used to handle the selectionchanged event: var movieList = document.getElementById("movieList"); var detailsTemplate = document.getElementById("detailsTemplate"); var movieDetails = document.getElementById("movieDetails"); // Setup selectionchanged handler movieList.winControl.addEventListener("selectionchanged", function (evt) { if (movieList.winControl.selection.count() > 0) { movieList.winControl.selection.getItems().then(function (items) { // Clear the template container movieDetails.innerHTML = ""; // Render the template detailsTemplate.winControl.render(items[0].data, movieDetails); }); } }); The code above sets up an event handler (listener) for the selectionchanged event. The event handler first verifies that an item has been selected in the ListView (selection.count() > 0). Next, the details for the movie are rendered using the movie details Template (we created this Template in the previous section). The Complete Code For the sake of completeness, I’ve included the complete code for the master/detail view below. I’ve included both the default.html, default.js, and movies.js files. Here is the final code for the default.html file: <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>ListViewMasterDetail</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- ListViewMasterDetail references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> <script type="text/javascript" src="js/movies.js"></script> <style type="text/css"> body { font-size: xx-large; } .movie { padding: 5px; } #masterDetail { display: -ms-box; } #movieList { width: 300px; margin: 20px; } #movieDetails { margin: 20px; } </style> </head> <body> <!-- Templates --> <div id="masterItemTemplate" data-win-control="WinJS.Binding.Template"> <div class="movie"> <span data-win-bind="innerText:title"></span> </div> </div> <div id="detailsTemplate" data-win-control="WinJS.Binding.Template"> <div> <div> Title: <span data-win-bind="innerText:title"></span> </div> <div> Director: <span data-win-bind="innerText:director"></span> </div> </div> </div> <!-- Master/Detail --> <div id="masterDetail"> <!-- Master --> <div id="movieList" data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource: ListViewDemos.movies.dataSource, itemTemplate: select('#masterItemTemplate'), tapBehavior: 'directSelect', selectionMode: 'single', layout: { type: WinJS.UI.ListLayout } }"> </div> <!-- Detail --> <div id="movieDetails"></div> </div> </body> </html> Here is the default.js file: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { WinJS.UI.processAll(); var movieList = document.getElementById("movieList"); var detailsTemplate = document.getElementById("detailsTemplate"); var movieDetails = document.getElementById("movieDetails"); // Setup selectionchanged handler movieList.winControl.addEventListener("selectionchanged", function (evt) { if (movieList.winControl.selection.count() > 0) { movieList.winControl.selection.getItems().then(function (items) { // Clear the template container movieDetails.innerHTML = ""; // Render the template detailsTemplate.winControl.render(items[0].data, movieDetails); }); } }); } }; app.start(); })();   Here is the movies.js file: (function () { "use strict"; var movies = new WinJS.Binding.List([ { title: "Star Wars", director: "Lucas"}, { title: "Shrek", director: "Adamson" }, { title: "Star Trek", director: "Abrams" }, { title: "Spiderman", director: "Raimi" }, { title: "Memento", director: "Nolan" }, { title: "Minority Report", director: "Spielberg" } ]); // Expose the data source WinJS.Namespace.define("ListViewDemos", { movies: movies }); })();   Summary The purpose of this blog entry was to describe how to create a simple master/detail view by taking advantage of the WinJS ListView control. We handled the selectionchanged event of the ListView control to display movie details when you select a movie in the ListView.

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  • Metro: Grouping Items in a ListView Control

    - by Stephen.Walther
    The purpose of this blog entry is to explain how you can group list items when displaying the items in a WinJS ListView control. In particular, you learn how to group a list of products by product category. Displaying a grouped list of items in a ListView control requires completing the following steps: Create a Grouped data source from a List data source Create a Grouped Header Template Declare the ListView control so it groups the list items Creating the Grouped Data Source Normally, you bind a ListView control to a WinJS.Binding.List object. If you want to render list items in groups, then you need to bind the ListView to a grouped data source instead. The following code – contained in a file named products.js — illustrates how you can create a standard WinJS.Binding.List object from a JavaScript array and then return a grouped data source from the WinJS.Binding.List object by calling its createGrouped() method: (function () { "use strict"; // Create List data source var products = new WinJS.Binding.List([ { name: "Milk", price: 2.44, category: "Beverages" }, { name: "Oranges", price: 1.99, category: "Fruit" }, { name: "Wine", price: 8.55, category: "Beverages" }, { name: "Apples", price: 2.44, category: "Fruit" }, { name: "Steak", price: 1.99, category: "Other" }, { name: "Eggs", price: 2.44, category: "Other" }, { name: "Mushrooms", price: 1.99, category: "Other" }, { name: "Yogurt", price: 2.44, category: "Other" }, { name: "Soup", price: 1.99, category: "Other" }, { name: "Cereal", price: 2.44, category: "Other" }, { name: "Pepsi", price: 1.99, category: "Beverages" } ]); // Create grouped data source var groupedProducts = products.createGrouped( function (dataItem) { return dataItem.category; }, function (dataItem) { return { title: dataItem.category }; }, function (group1, group2) { return group1.charCodeAt(0) - group2.charCodeAt(0); } ); // Expose the grouped data source WinJS.Namespace.define("ListViewDemos", { products: groupedProducts }); })(); Notice that the createGrouped() method requires three functions as arguments: groupKey – This function associates each list item with a group. The function accepts a data item and returns a key which represents a group. In the code above, we return the value of the category property for each product. groupData – This function returns the data item displayed by the group header template. For example, in the code above, the function returns a title for the group which is displayed in the group header template. groupSorter – This function determines the order in which the groups are displayed. The code above displays the groups in alphabetical order: Beverages, Fruit, Other. Creating the Group Header Template Whenever you create a ListView control, you need to create an item template which you use to control how each list item is rendered. When grouping items in a ListView control, you also need to create a group header template. The group header template is used to render the header for each group of list items. Here’s the markup for both the item template and the group header template: <div id="productTemplate" data-win-control="WinJS.Binding.Template"> <div class="product"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> </div> <div id="productGroupHeaderTemplate" data-win-control="WinJS.Binding.Template"> <div class="productGroupHeader"> <h1 data-win-bind="innerText: title"></h1> </div> </div> You should declare the two templates in the same file as you declare the ListView control – for example, the default.html file. Declaring the ListView Control The final step is to declare the ListView control. Here’s the required markup: <div data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource:ListViewDemos.products.dataSource, itemTemplate:select('#productTemplate'), groupDataSource:ListViewDemos.products.groups.dataSource, groupHeaderTemplate:select('#productGroupHeaderTemplate'), layout: {type: WinJS.UI.GridLayout} }"> </div> In the markup above, six properties of the ListView control are set when the control is declared. First the itemDataSource and itemTemplate are specified. Nothing new here. Next, the group data source and group header template are specified. Notice that the group data source is represented by the ListViewDemos.products.groups.dataSource property of the grouped data source. Finally, notice that the layout of the ListView is changed to Grid Layout. You are required to use Grid Layout (instead of the default List Layout) when displaying grouped items in a ListView. Here’s the entire contents of the default.html page: <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>ListViewDemos</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- ListViewDemos references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> <script src="/js/products.js" type="text/javascript"></script> <style type="text/css"> .product { width: 200px; height: 100px; border: white solid 1px; font-size: x-large; } </style> </head> <body> <div id="productTemplate" data-win-control="WinJS.Binding.Template"> <div class="product"> <span data-win-bind="innerText:name"></span> <span data-win-bind="innerText:price"></span> </div> </div> <div id="productGroupHeaderTemplate" data-win-control="WinJS.Binding.Template"> <div class="productGroupHeader"> <h1 data-win-bind="innerText: title"></h1> </div> </div> <div data-win-control="WinJS.UI.ListView" data-win-options="{ itemDataSource:ListViewDemos.products.dataSource, itemTemplate:select('#productTemplate'), groupDataSource:ListViewDemos.products.groups.dataSource, groupHeaderTemplate:select('#productGroupHeaderTemplate'), layout: {type: WinJS.UI.GridLayout} }"> </div> </body> </html> Notice that the default.html page includes a reference to the products.js file: <script src=”/js/products.js” type=”text/javascript”></script> The default.html page also contains the declarations of the item template, group header template, and ListView control. Summary The goal of this blog entry was to explain how you can group items in a ListView control. You learned how to create a grouped data source, a group header template, and declare a ListView so that it groups its list items.

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