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  • Thread used for ServiceConnection callback (Android)

    - by Jannick
    Hi I'm developing an activity that binds to a local service (in onCreate of the activity): bindService(new Intent(this, CommandService.class), svcConn, BIND_AUTO_CREATE); I would like to be able to call methods through the IBinder in my lifecycle methods, but can not be sure that onServiceConnected have been called prior to these. I'm thinking of handling this by adding a queue of sorts in the ServiceConnection implementation, so that the method calls (Command pattern) will be executed once the connection is established. My questions are then: Is this stupid, any better ways? :) Are there any specification for which thread will be used to execute the ServiceConnection callbacks? More to the point, do I need to worry about synchronizing a queue datastructure? Edit - something like: public void onServiceConnected(ComponentName name, IBinder service) { dispatchService = (DispatchAsync)service; for(ExecutionTask task : queue){ dispatchService.execute(task.getCommand(), task); } }

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  • How can I measure TForm deserialization time in Delphi?

    - by mjustin
    For performance tests I need a way to measure the time needed for a form to load its definition from the DFM. All existing forms inherit a custom form class. To capture the current time, this base class needs overriden methods as "extension points": before the beginning of the deserialization process after the completion of deserialization (can be implemented by overriding the Loaded procedure) the moment just before the execution of the OnFormCreate event Which TObject (or TComponent) methods are best suited? Maybe there are other extension points in the form creation process, please feel free to make suggestions.

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  • How can unit testing make parameter validation redundant?

    - by Johann Gerell
    We have a convention to validate all parameters of constructors and public functions/methods. For mandatory parameters of reference type, we mainly check for non-null and that's the chief validation in constructors, where we set up mandatory dependencies of the type. The number one reason why we do this is to catch that error early and not get a null reference exception a few hours down the line without knowing where or when the faulty parameter was introduced. As we start transitioning to more and more TDD, some team members feel the validation is redundant. Uncle Bob, who is a vocal advocate of TDD, strongly advices against doing parameter validation. His main argument seems to be "I have a suite of unit tests that makes sure everything works". But I can for the life of it just not see in what way unit tests can prevent our developers from calling these methods with bad parameters in production code. Please, unit testers out there, if you could explain this to me in a rational way with concrete examples, I'd be more than happy to seize this parameter validation!

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  • No GPS Update retrieved? Problem in Code?

    - by poeschlorn
    Hello mates, I've got a serious problem with my GPS on my Nexus One: I wrote a kind of hello world with GPS, but the Toast that should be displayed isn't :( I don't know what I'm doing wrong...maybe you could help me getting this work. Here's my code: package gps.test; import android.app.Activity; import android.content.Context; import android.location.Location; import android.location.LocationListener; import android.location.LocationManager; import android.os.Bundle; import android.widget.Toast; public class GPS extends Activity { private LocationManager lm; private LocationListener locationListener; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); // ---use the LocationManager class to obtain GPS locations--- lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE); locationListener = new MyLocationListener(); lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 100, 1, locationListener); } private class MyLocationListener implements LocationListener { @Override public void onLocationChanged(Location loc) { if (loc != null) { Toast.makeText( getBaseContext(), "Location changed : Lat: " + loc.getLatitude() + " Lng: " + loc.getLongitude(), Toast.LENGTH_SHORT).show(); } } @Override public void onProviderDisabled(String provider) { // TODO Auto-generated method stub } @Override public void onProviderEnabled(String provider) { // TODO Auto-generated method stub } @Override public void onStatusChanged(String provider, int status, Bundle extras) { // TODO Auto-generated method stub } } } Theoretically there should be a new toast every 100 milliseconds, shouldn't it? Or at least, when I change my position by one meter!? I've no idea why it doesn't. I must admit I'm new to the topic, maybe I've missed something? It would be great if you could give me a hint :) nice greetings, poeschlorn

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  • How to decide between using PLINQ and LINQ at runtime?

    - by Hamish Grubijan
    Or decide between a parallel and a sequential operation in general. It is hard to know without testing whether parallel or sequential implementation is best due to overhead. Obviously it will take some time to train "the decider" which method to use. I would say that this method cannot be perfect, so it is probabilistic in nature. The x,y,z do influence "the decider". I think a very naive implementation would be to give both 1/2 chance at the beginning and then start favoring them according to past performance. This disregards x,y,z, however. I suspect that this question would be better answered by academics than practitioners. Anyhow, please share your heuristic, your experience if any, your tips on this. Sample code: public interface IComputer { decimal Compute(decimal x, decimal y, decimal z); } public class SequentialComputer : IComputer { public decimal Compute( ... // sequential implementation } public class ParallelComputer : IComputer { public decimal Compute( ... // parallel implementation } public class HybridComputer : IComputer { private SequentialComputer sc; private ParallelComputer pc; private TheDecider td; // Helps to decide between the two. public HybridComputer() { sc = new SequentialComputer(); pc = new ParallelComputer(); td = TheDecider(); } public decimal Compute(decimal x, decimal y, decimal z) { decimal result; decimal time; if (td.PickOneOfTwo() == 0) { // Time this and save result into time. result = sc.Compute(...); } else { // Time this and save result into time. result = pc.Compute(); } td.Train(time); return result; } }

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  • GPS not update location after close and reopen app on android

    - by mrmamon
    After I closed my app for a while then reopen it again,my app will not update location or sometime it will take long time( about 5min) before update. How can I fix it? This is my code private LocationManager lm; private LocationListener locationListener; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE); locationListener = new mLocationListener(); lm.requestLocationUpdates( LocationManager.GPS_PROVIDER, 0, 0, locationListener); } private class myLocationListener implements LocationListener { @Override public void onLocationChanged(Location loc) { if (loc != null) { TextView gpsloc = (TextView) findViewById(R.id.widget28); gpsloc.setText("Lat:"+loc.getLatitude()+" Lng:"+ loc.getLongitude()); } } @Override public void onProviderDisabled(String provider) { // TODO Auto-generated method stub TextView gpsloc = (TextView) findViewById(R.id.widget28); gpsloc.setText("GPS OFFLINE."); } @Override public void onProviderEnabled(String provider) { // TODO Auto-generated method stub } @Override public void onStatusChanged(String provider, int status, Bundle extras) { // TODO Auto-generated method stub } }

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  • How to avoid exceptions catches copy-paste in .NET

    - by Budda
    Working with .NET framework I have a service with a set of methods that can generates several types of exceptions: MyException2, MyExc1, Exception... To provide proper work for all methods, each of them contains following sections: void Method1(...) { try { ... required functionality } catch(MyException2 exc) { ... process exception of MyException2 type } catch(MyExc1 exc) { ... process exception of MyExc1 type } catch(Exception exc) { ... process exception of Exception type } ... process and return result if necessary } It is very boring to have exactly same stuff in EACH service method with exactly same exceptions processing functionality... Is there any possibility to "group" these catch-sections and use only one line (something similar to C++ macros)? Probably something new in .NET 4.0 is related to this topic? Thanks. P.S. Any thoughts are welcome.

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  • Query String to Object with strongly typed properties

    - by Kamar
    Let’s say we track 20 query string parameters in our site. Each request which comes will have only a subset of those 20 parameters. But we definitely look for all/most of the parameters which comes in each request. We do not want to loop through the collection each time we are looking for a particular parameter initially or somewhere down the pipeline in the code. So we loop once through the query string collection, convert string values to their respective types (enums, int, string etc.), populate to QueryString object which is added to the context. After that wherever its needed we will have a strongly typed properties in the QueryString object which is easy to use and we maintain a standard. public class QueryString { public int Key1{ get; private set; } public SomeType Key2{ get; private set; } private QueryString() { } public static QueryString GetQueryString() { QueryString l_QS = new QueryString(); foreach (string l_Key in HttpContext.Current.Request.QueryString.AllKeys) { switch (l_Key) { case "key1": l_QS.Key1= DoSomething(l_Key, HttpContext.Current.Request.QueryString[l_Key]); break; case "key2": l_QS.Key2 = DoAnotherThing(l_Key, HttpContext.Current.Request.QueryString[l_Key]); break; } } return l_QS; } } Any other solution to achieve this?

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  • Calling this[int index] via reflection

    - by tkutter
    I try to implement a reflection-based late-bound library to Microsoft Office. The properties and methods of the Offce COM objects are called the following way: Type type = Type.GetTypeFromProgID("Word.Application"); object comObject = Activator.CreateInstance(type); type.InvokeMember(<METHOD NAME>, <BINDING FLAGS>, null, comObject, new object[] { <PARAMS>}); InvokeMember is the only possible way because Type.GetMethod / GetProperty works improperly with the COM objects. Methods and properties can be called using InvokeMember but now I have to solve the following problem: Method in the office-interop wrapper: Excel.Workbooks wb = excel.Workbooks; Excel.Workbook firstWb = wb[0]; respectively foreach(Excel.Workbook w in excel.Workbooks) // doSmth. How can I call the this[int index] operator of Excel.Workbooks via reflection?

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  • Connecting data to a GUI - OOP

    - by tau
    I have an application with several graphs and tables on it. I worked fast and just made classes like Graph and Table that each contained a request object (pseudo-code): class Graph { private request; public function setDateRange(dateRange) { request.setDateRange(dateRange); } public function refresh() { request.getData(function() { //refresh the display }); } } Upon a GUI event (say, someone changes the date range dropdown), I'd just call the setters on the Graph instance and then refresh it. Well, when I added other GUI elements like tables and whatnot, they all basically had similar methods (setDateRange and other things common to the request). What are some more elegant OOP ways of doing this? The application is very simple and I don't want to over-architect it, but I also don't want to have a bunch of classes with basically the same methods that are just routing to a request object. I also don't want to set up each GUI class as inheriting from the request class, but I'm open to any ideas really.

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  • How to test code built to save/restore Lifecycle of an Activity?

    - by Pentium10
    How can I test all of the following methods code? I want to play scenarios when all of them are happening to see if my code works for save/restore process of an activity. So what should I do in the Emulator to get all methods tested? public class Activity extends ApplicationContext { protected void onCreate(Bundle savedInstanceState); protected void onStart(); protected void onRestart(); protected void onResume(); protected void onPause(); protected void onStop(); protected void onDestroy(); }

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  • java: retrieving the "canonical value" from a Set<T> where T has a custom equals()

    - by Jason S
    I have a class Foo which overrides equals() and hashCode() properly. I would like to also would like to use a HashSet<Foo> to keep track of "canonical values" e.g. I have a class that I would like to write like this, so that if I have two separate objects that are equivalent I can coalesce them into references to the same object: class Canonicalizer<T> { final private Set<T> values = new HashSet<T>(); public T findCanonicalValue(T value) { T canonical = this.values.get(value); if (canonical == null) { // not in the set, so put it there for the future this.values.add(value); return value; } else { return canonical; } } } except that Set doesn't have a "get" method that would return the actual value stored in the set, just the "contains" method that returns true or false. (I guess that it assumes that if you have an object that is equal to a separate object in the set, you don't need to retrieve the one in the set) Is there a convenient way to do this? The only other thing I can think of is to use a map and a list: class Canonicalizer<T> { // warning: neglects concurrency issues final private Map<T, Integer> valueIndex = new HashMap<T, Integer>(); final private List<T> values = new ArrayList<T>(); public T findCanonicalValue(T value) { Integer i = this.valueIndex.get(value); if (i == null) { // not in the set, so put it there for the future i = this.values.size(); this.values.add(value); this.valueIndex.put(value, i); return value; } else { // in the set return this.values.get(i); } } }

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  • Modifying annotation attribute value at runtime in java

    - by Lici
    Hi folks: some methods in our model pojos have been annotated like this: @Column(name="cli_clipping_id", updatable=false, columnDefinition = "varchar(" + ModelUtils.ID_LENGTH + ") COLLATE utf8_bin") columnDefinition attribute is database vendor dependant, so when trying to drop schema in HSQLDB using Hibernate it fails: [ERROR] 16 jun 12:58:42.480 PM main [org.hibernate.tool.hbm2ddl.SchemaExport] Unexpected token: COLLATE in statement [create table cms.edi_editorial_obj (edi_uuid varchar(23) COLLATE ] To fix this, i'm thinking on this solution (but don't want to spend time if it isn't possible) , at runtime, for each method column annotated: Get @Column annotation Create a copy of the column annotation, setting columnDefinition null using javaassist. set column method annotation to the copy column annotation object overriding the old one (i don't know it this is possible) Is it possible to "hack" these methods this way? Any help would be much appreciated ...

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  • How do I keep track of the session for each servlet request, until I use it? Singletons wont work?

    - by corgrath
    For each servlet request I get, I pass, perhaps, 10 methods before I am at where I need to check something in the session and I need the HttpSession. The only way I can get the HttpSession is from the HttpServletRequest, correct? How do I keep track of the session for each servlet request? Unfortuantly I cannot simple make a singleton (ex, SessionInformation.instance().getAttribute("name")) because that session would then be used over all requests. Is there a way to store the session globally for each request without having to pass it (or it's information) down all the methods just in case I need it?

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  • Should my validator have access to my entire model?

    - by wb
    As the title states I'm wondering if it's a good idea for my validation class to have access to all properties from my model. Ideally, I would like to do that because some fields require 10+ other fields to verify whether it is valid or not. I could but would rather not have functions with 10+ parameters. Or would that make the model and validator too coupled with one another? Here is a little example of what I mean. This code however does not work because it give an infinite loop! Class User Private m_UserID Private m_Validator Public Sub Class_Initialize() End Sub Public Property Let Validator(value) Set m_Validator = value m_Validator.Initialize(Me) End Property Public Property Get Validator() Validator = m_Validator End Property Public Property Let UserID(value) m_UserID = value End property Public Property Get UserID() UserID = m_Validator.IsUserIDValid() End property End Class Class Validator Private m_User Public Sub Class_Initialize() End Sub Public Sub Initialize(value) Set m_User = value End Sub Public Function IsUserIDValid() IsUserIDValid = m_User.UserID > 13 End Function End Class Dim mike : Set mike = New User mike.UserID = 123456 mike.Validator = New Validator Response.Write mike.UserID If I'm right and it is a good idea, how can I go a head and fix the infinite loop with the get property UserID? Thank you.

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  • Method for exporting drawn flash/flex UIComponent to vector based print file

    - by eshowcase
    Hi, I am creating a flex application where I am using the built in graphics package of flex 3 to draw shapes and things to a UIComponent. I want to be able to export this vector image UIComponent to a vector based file, pdf, eps etc. Are there any tools, libraries, or methods for doing so? I looked at AlivePDF - which works very slick, but its output is effectively a snapshot of the UIComponent drawn out as a bitmap to the PDF. I want true vector output, as this image is for print, needs to be able to scale and be color correct. I read somewhere that it may be possible with Adobe Live Cycle, but in looking at the documentation I'm not sure how to use it. Another possibility is to submit the final image parameters to a server-side PHP script that would re-generate the image in SVG format. But as I understand SVG is not ideal for print, and this is lots of extra work. Any thoughts, ideas, methods? Thanks!

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  • WPF validation on Enter Key Up

    - by Martin
    I'm trying to validate a UI change when Enter key is pressed. The UI element is a textbox, which is data binded to a string. My problem is that the data binding hasn't updated TestText when Enter key is Up. It is only updated when I press the button which brings up a message box. /// <summary> /// Interaction logic for Window1.xaml /// </summary> public partial class Window1 : Window, INotifyPropertyChanged { String _testText = new StringBuilder("One").ToString(); public string TestText { get { return _testText; } set { if (value != _testText) { _testText = value; OnPropertyChanged("TestText"); } } } public Window1() { InitializeComponent(); myGrid.DataContext = this; } private void OnPropertyChanged(string property) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(property)); } } public event PropertyChangedEventHandler PropertyChanged; private void onKeyUp(object sender, KeyEventArgs e) { if (e.Key != System.Windows.Input.Key.Enter) return; System.Diagnostics.Trace.WriteLine(TestText); } private void button1_Click(object sender, RoutedEventArgs e) { MessageBox.Show(TestText); } } Window XAML: Window x:Class="VerificationTest.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="Window1" Height="300" Width="300" KeyUp="onKeyUp" TextBox XAML: TextBox Name="myTextBox" Text="{Binding TestText}" Button XAML: Button Name="button1" Click="button1_Click"

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  • problem with drag and drop for the winform using c#

    - by karthik
    I dont have the title bar in my winform, so i need to code drag and drop for the entire form. I am using the below code to do it, which works fine. I have two panels in my form, PanelA and PanelB. During the startup i show PanelA where the drag and drop works perfectly. Later when the user clicks the button in PannelA, i need to make PanelA visible false and show the PanelB My drag and drop is not working when the PanelB is loaded in form. Whats the problem here ? private void SerialPortScanner_MouseUp(object sender, MouseEventArgs e) { this.drag = false; } private void SerialPortScanner_MouseDown(object sender, MouseEventArgs e) { this.drag = true; this.start_point = new Point(e.X, e.Y); } private void SerialPortScanner_MouseMove(object sender, MouseEventArgs e) { if (this.drag) { Point p1 = new Point(e.X, e.Y); Point p2 = this.PointToScreen(p1); Point p3 = new Point(p2.X - this.start_point.X, p2.Y - this.start_point.Y); this.Location = p3; } }

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  • Message Handlers and the WeakReference issue

    - by user1058647
    The following message Handler works fine receiving messages from my service... private Handler handler = new Handler() { public void handleMessage(Message message) { Object path = message.obj; if (message.arg1 == 5 && path != null) //5 means its a single mapleg to plot on the map { String myString = (String) message.obj; Gson gson = new Gson(); MapPlot mapleg = gson.fromJson(myString, MapPlot.class); myMapView.getOverlays().add(new DirectionPathOverlay(mapleg.fromPoint, mapleg.toPoint)); mc.animateTo(mapleg.toPoint); } else { if (message.arg1 == RESULT_OK && path != null) { Toast.makeText(PSActivity.this, "Service Started" + path.toString(), Toast.LENGTH_LONG).show(); } else { Toast.makeText(PSActivity.this,"Service error" + String.valueOf(message.arg1), Toast.LENGTH_LONG).show(); } } }; }; However, even though it tests out alright in the AVD (I'm feeding it a large KML file via DDMS) the "object path = message.obj;" line has a WARNING saying "this Handler class should be static else leaks might occur". But if I say "static Handler handler = new Handler()" it won't compile complaining that I "cannot make a static reference to a non-static field myMapView. If I can't make such references, I can't do anything useful. This led me into several hours of googling around on this issue and learning more about weakReferences than I ever wanted to know. The often found reccomendation I find is that I should replace... private Handler handler = new Handler() with static class handler extends Handler { private final WeakReference<PSActivity> mTarget; handler(PSActivity target) { mTarget = new WeakReference<PSActivity>(target); } But this won't compile still complaining that I can't make a static reference to a non-dtatic field. So, my question a week or to ago was "how can I write a message handler for android so my service can send data to my activity. Even though I have working code, the question still stands with the suffix "without leaking memory". Thanks, Gary

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  • Dynamic Dispatch without Virtual Functions

    - by Kristopher Johnson
    I've got some legacy code that, instead of virtual functions, uses a kind field to do dynamic dispatch. It looks something like this: // Base struct shared by all subtypes // Plain-old data; can't use virtual functions struct POD { int kind; int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); }; enum Kind { Kind_Derived1, Kind_Derived2, Kind_Derived3 }; struct Derived1: POD { Derived1(): kind(Kind_Derived1) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; struct Derived2: POD { Derived2(): kind(Kind_Derived2) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; struct Derived3: POD { Derived3(): kind(Kind_Derived3) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; and then the POD class's function members are implemented like this: int POD::GetFoo() { // Call kind-specific function switch (kind) { case Kind_Derived1: { Derived1 *pDerived1 = static_cast<Derived1*>(this); return pDerived1->GetFoo(); } case Kind_Derived2: { Derived2 *pDerived2 = static_cast<Derived2*>(this); return pDerived2->GetFoo(); } case Kind_Derived3: { Derived3 *pDerived3 = static_cast<Derived3*>(this); return pDerived3->GetFoo(); } default: throw UnknownKindException(kind, "GetFoo"); } } POD::GetBar(), POD::GetBaz(), POD::GetXyzzy(), and other members are implemented similarly. This example is simplified. The actual code has about a dozen different subtypes of POD, and a couple dozen methods. New subtypes of POD and new methods are added pretty frequently, and so every time we do that, we have to update all these switch statements. The typical way to handle this would be to declare the function members virtual in the POD class, but we can't do that because the objects reside in shared memory. There is a lot of code that depends on these structs being plain-old-data, so even if I could figure out some way to have virtual functions in shared-memory objects, I wouldn't want to do that. So, I'm looking for suggestions as to the best way to clean this up so that all the knowledge of how to call the subtype methods is centralized in one place, rather than scattered among a couple dozen switch statements in a couple dozen functions. What occurs to me is that I can create some sort of adapter class that wraps a POD and uses templates to minimize the redundancy. But before I start down that path, I'd like to know how others have dealt with this.

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  • Determine when a NSOpenPanel will close

    - by Martin
    I'm trying to determine when an NSOpenPanel is closing before it actually closes. I need to do this so I can overlay another window with a screenshot of the open panel on top of it to be animated. Unfortunately, all the notifications that you seem to be able to access seem to fire AFTER the window's already been closed. This leads to a jarring stutter before you start your transition. I've tried: - using NSWindow delegate methods on the open panel (apparently, none of the NSWindow delegate methods work) - monitoring panel:userEnteredFilename:confirmed: (not called) - showing the dialog with a callback (callback happens AFTER the panel disappears)

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  • WPF Prism's delegatecommand not refreshing

    - by gkar
    I am building wpf edit form, that has two buttons, BeginEdit and Save And the form is bound to ViewModel that inherits from Prism's NotificationObject. There is a property called IsReadOnly And there are two commands that are Prism's DelegateCommands BeginEdit command and save command The code is here private DelegateCommand _beginEdit; public DelegateCommand BeginEdit { get { return _beginEdit ?? (_beginEdit = new DelegateCommand(() => this.IsReadOnly = false , () => IsReadOnly)); } } private bool _isReadOnly; public bool IsReadOnly { get { return _isReadOnly; } set { _isReadOnly = value; RaisePropertyChanged("IsReadOnly"); } } private DelegateCommand _saveEdit; public DelegateCommand SaveEdit { get { return _saveEdit ?? (_saveEdit = new DelegateCommand(() => this.IsReadOnly = true , () => !IsReadOnly)); } } So, as you see, the command will set IsReadOnly property to true or false, and CanExecute should get its value from the same property as well. It works when I start the form. But after I press BeginEdit, the buttons stays as the same, and the canExecute is not reflecting the new value of IsReadOnly

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  • Need to create a string token dynamically base on which method is calling it

    - by sa
    This is a minimal code. I have the string Str which is used by various methods. I want to in getId method be able to do 2 things Assign class="PDP" to it and Give it a value3 So the final string looks like <tr class='PDP' id='{2}'> <td {0}</td><td>{1}</td></tr> But please note that I will need different values for class in different methods so some Str will have PDP, another will have PTM etc. Is there a clean way to achieve this . private const string Str = "<tr><td >{0}</td><td>{1}</td></tr>"; public static string getId() { string field=string.Format(str, value1,value2, found=true? value3:""); }

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  • Are there any garanties in JLS about order of execution static initialization blocks?

    - by Roman
    I wonder if it's reliable to use a construction like: private static final Map<String, String> engMessages; private static final Map<String, String> rusMessages; static { engMessages = new HashMap<String, String> () {{ put ("msgname", "value"); }}; rusMessages = new HashMap<String, String> () {{ put ("msgname", "????????"); }}; } private static Map<String, String> msgSource; static { msgSource = engMessages; } public static String msg (String msgName) { return msgSource.get (msgName); } Is there a possibility that I'll get NullPointerException because msgSource initialization block will be executed before the block which initializes engMessages? (about why don't I do msgSource initialization at the end of upper init. block: just the matter of taste; I'll do so if the described construction is unreliable)

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  • Why won't WPF databindings show text when ToString() has a collaborating object?

    - by Jay
    In a simple form, I bind to a number of different objects -- some go in listboxes; some in textblocks. A couple of these objects have collaborating objects upon which the ToString() method calls when doing its work -- typically a formatter of some kind. When I step through the code I see that when the databinding is being set up, ToString() is called the collaborating object is not null and returns the expected result when inspected in the debugger, the objects return the expected result from ToString() BUT the text does not show up in the form. The only common thread I see is that these use a collaborating object, whereas the other bindings that show up as expected simply work from properties and methods of the containing object. If this is confusing, here is the gist in code: public class ThisThingWorks { private SomeObject some_object; public ThisThingWorks(SomeObject s) { some_object = s; } public override string ToString() { return some_object.name; } } public class ThisDoesntWork { private Formatter formatter; private SomeObject some_object; public ThisDoesntWork(SomeObject o, Formatter f) { formatter = f; some_object = o; } public override string ToString() { return formatter.Format(some_object.name); } } Again, let me reiterate -- the ToString() method works in every other context -- but when I bind to the object in WPF and expect it to display the result of ToString(), I get nothing. Update: The issue seems to be what I see as a buggy behaviour in the TextBlock binding. If I bind the Text property to a property of the DataContext that is declared as an interface type, ToString() is never called. If I change the property declaration to an implementation of the interface, it works as expected. Other controls, like Label work fine when binding the Content property to a DataContext property declared as either the implementation or the interface. Because this is so far removed from the title and content of this question, I've created a new question here: http://stackoverflow.com/questions/2917878/why-doesnt-textblock-databinding-call-tostring-on-a-property-whose-compile-tim

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