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  • GWT (Google Web Toolkit) Designer not working on Ubuntu 12.10

    - by Marian Lux
    The GWT Desinger is not working on Ubuntu 12.10. It worked on Ubuntu 12.04. I installed the Eclipse Plugin as described on the GWT Homepate If I want to open the Design-View (for an xml-GWT-File), Eclipse crashes (prompt closing of the application). I found this two workarounds for which are for 12.04 (but on 12.04 i did not need this to get it working - it worked out of the box for me). I tried them on my 12.10 Ubuntu but they are not working. But I have to say that I can't find the "Use WebKit for rendering GWT UI (if available)"-Flag. What can I do to get the GWT Designer working? I tested it successfully again on a 12.04 Ubuntu VMware image. If I don't get a solution, I have to downgrade my Ubuntu to 12.04 again.

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  • Is there any software to clip a website, make changes to the code and republish it?

    - by user1445919
    I am working in the front end of an application and we provide the interface between the customers and several backend services. We have been using Kapow software to clip the html/jsp code we receive from the backend, make the necessary changes and publish them on the main website. I wanted to know if there is any other alternative to this software which suffices our requirement. Also, are any of those open source?

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  • Collision checking problem on a Tiled map

    - by nosferat
    I'm working on a pacman styled dungeon crawler, using the free oryx sprites. I've created the map using Tiled, separating the floor, walls and treasure in three different layers. After importing the map in libGDX, it renders fine. I also added the player character, for now it just moves into one direction, the player cannot control it yet. I wanted to add collision and I was planning to do this by checking if the player's new position is on a wall tile. Therefore as you can see in the following code snippet, I get the tile type of the appropriate tile and if it is not zero (since on that layer there is nothing except the wall tile) it is a collision and the player cannot move further: final Vector2 newPos = charController.move(warrior.getX(), warrior.getY()); if(!collided(newPos)) { warrior.setPosition(newPos.x, newPos.y); warrior.flip(charController.flipX(), charController.flipY()); } [..] private boolean collided(Vector2 newPos) { int row = (int) Math.floor((newPos.x / 32)); int col = (int) Math.floor((newPos.y / 32)); int tileType = tiledMap.layers.get(1).tiles[row][col]; if (tileType == 0) { return false; } return true; } The character only moves one tile with this code: If I reduce the col value by two it two more tiles. I think the problem will be around indexing, but I'm totally confused because the zero in the coordinate system of libGDX is in the bottom left corner of the screen, and I don't know the tiles array's indexing is similair or not. The size of the map is 19x21 tiles and looks like the following (the starting position of the player is marked with blue:

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  • get stick analogue XY position using Jinput in lwjgl

    - by oIrC
    i want to capture the movement of the analogue stick of the gamePad. is there any equivalent function to this public void mouseMoved(MouseEvent mouseEvent) { mouseEvent.getX(); //return the X coordinate of the cursor inside a component mouseEvent.getY();//return the Y coordinate of the cursor inside a component } into lwjgl.input.Controllers, i found controller.getAxisValue() but this one doesn't work as the function above. any help? thanks.

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  • how should I design Objects around this business requirement?

    - by brainydexter
    This is the business requirement: " A Holiday Package (e.g. New York NY Holiday Package) can be offered in different ways based on the Origin city: From New Delhi to NY From Bombay to NY NY itself ( Land package ) (Bold implies default selection) a. and b. User can fly from either New Delhi or Bombay to NY. c. NY is a Land package, where a user can reach NY by himself and is a standalone holidayPackage. " Let's say I have a class that represents HolidayPackage, Destination (aka City). public class HolidayPackage{ Destination holidayCity; ArrayList<BaseHolidayPackageVariant> variants; BaseHolidayPackageVariant defaultVariant; } public abstract class BaseHolidayPackageVariant { private Integer variantId; private HolidayPackage holidayPackage; private String holidayPackageType; } public class LandHolidayPackageVariant extends BaseHolidayPackageVariant{ } public class FlightHolidayPackageVariant extends BaseHolidayPackageVariant{ private Destination originCity; } What data structure/objects should I design to support: options a default within those options Sidenote: A HolidayPackage can also be offered in different ways based on Hotel selections. I'd like to follow a design which I can leverage to support that use case in the future. This is the backend design I have in mind.

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  • Problem when scaling game screen in Libgdx

    - by Nicolas Martel
    Currently, I'm able to scale the screen by applying this bit of code onto an OrthographicCamera Camera.setToOrtho(true, Gdx.graphics.getWidth() / 2, Gdx.graphics.getHeight() / 2); But something quite strange is happening with this solution, take a look at this picture of my game below Seems fine right? But upon further investigation, many components are rendered off by one pixels, and the tiles all are. Take a closer look I circled a couple of the errors. Note that the shadow of the warrior I circled appears fine for the other warriors. Also keep in mind that everything is rendered at pixel-perfect precision when I disable the scaling. I actually thought of a possible source for the problem as I'm writing this but I decided to still post this because I would assume somebody else might run into the same issue.

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  • Is implementing an interface defined in a subpackage an anti-pattern?

    - by Michael Kjörling
    Let's say I have the following: package me.my.pkg; public interface Something { /* ... couple of methods go here ... */ } and: package me.my; import me.my.pkg.Something; public class SomeClass implements Something { /* ... implementation of Something goes here ... */ /* ... some more method implementations go here too ... */ } That is, the class implementing an interface lives closer to the package hierarchy root than does the interface it implements but they both belong in the same package hierarchy. The reason for this in the particular case I have in mind is that there is a previously-existing package that groups functionality which the Something interface logically belongs to, and the logical (as in both "the one you'd expect" and "the one where it needs to go given the current architecture") implementation class exists previously and lives one level "up" from the logical placement of the interface. The implementing class does not logically belong anywhere under me.my.pkg. In my particular case, the class in question implements several interfaces, but that feels like it doesn't make any (or at least no significant) difference here. I can't decide if this is an acceptable pattern or not. Is it or is it not, and why?

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  • Movement in RPG

    - by user1264811
    I want to make an RPG game in which I move tile by tile. So when I hit up, the tile row that I am on decreases by one for example. Also, it's supposed to be a slow movement so that I can see the change in tile, i.e. I can see my sprite move from tile to tile. Currently, with the code I have, when I hit a direction on my keyboard, I move several blocks within seconds and by the time I release the button I have already gotten a nullPointerException error because I have left the map. How can I slow down the movement?

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  • Problem inserting pre-ordered values to quadtree

    - by Lucas Corrêa Feijó
    There's this string containing B, W and G (standing for black, white and gray). It defines the pre-ordered path of the quadtree I want to build. I wrote this method for filling the QuadTree class I also wrote but it doesn't work, it inserts correctly until it reaches a point in the algorithm it needs to "return". I use math quadrants convention order for insertion, such as northeast, northwest, southwest and southeast. A quadtree has all it's leafs black or white and all the other nodes gray The node used in the tree is called Node4T and has a char as data and 4 references to other nodes like itself, called, respectively NE, NW, SW, SE. public void insert(char val) { if(root==null) { root = new Node4T(val); } else { insert(root, val); } } public void insert(Node4T n, char c) { if(n.data=='G') // possible to insert { if(n.NE==null) { n.NE = new Node4T(c); return; } else { insert(n.NE,c); } if(n.NW==null) { n.NW = new Node4T(c); return; } else { insert(n.NW,c); } if(n.SW==null) { n.SW = new Node4T(c); return; } else { insert(n.SW,c); } if(n.SE==null) { n.SE = new Node4T(c); return; } else { insert(n.SE,c); } } else // impossible to insert { } } The input "GWGGWBWBGBWBWGWBWBWGGWBWBWGWBWBGBWBWGWWWB" is given a char at a time to the insert method and then the print method is called, pre-ordered, and the result is "GWGGWBWBWBWGWBWBW". How do I make it import the string correctly? Ignore the string reading process, suppose the method is called and it has to do it's job.

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  • Sending Graphics to the C drive [on hold]

    - by CodeOfGenius
    I'm trying to create image files on the users' desktop. Let's say i have a picture of an orange in my eclipse workspace in the resource folder. When somebody downloads the project, I want to take that image of an orange and put it in a folder called fruit on their desktop. Whenever i export my game it can't read the images anymore which is wierd so I prefer to try this method. Just like minecraft has its' stuff in %Appdata%, I want to put a folder with my images the game uses on the desktop. There isn't any errors, I'm just asking how do i do this.

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  • Naming your unit tests

    - by kerry
    When you create a test for your class, what kind of naming convention do you use for the tests? How thorough are your tests? I have lately switched from the conventional camel case test names to lower case letters with underscores. I have found this increases the readability and causes me to write better tests. A simple utility class: public class ArrayUtils { public static T[] gimmeASlice(T[] anArray, Integer start, Integer end) { // implementation (feeling lazy today) } } I have seen some people who would write a test like this: public class ArrayUtilsTest { @Test public void testGimmeASliceMethod() { // do some tests } } A more thorough and readable test would be: public class ArrayUtilsTest { @Test public void gimmeASlice_returns_appropriate_slice() { // ... } @Test public void gimmeASlice_throws_NullPointerException_when_passed_null() { // ... } @Test public void gimmeASlice_returns_end_of_array_when_slice_is_partly_out_of_bounds() { // ... } @Test public void gimmeASlice_returns_empty_array_when_slice_is_completely_out_of_bounds() { // ... } } Looking at this test, you have no doubt what the method is supposed to do. And, when one fails, you will know exactly what the issue is.

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  • Is it time to deprecate synchronized, wait and notify?

    - by OldCurmudgeon
    Is there a single scenario (other than compatibility with ancient JVMs) where using synchronized is preferable to using a Lock? Can anyone justify using wait or notify over the newer systems? Is there any algorithm that must use one of them in its implementation? I see a previous questions that touched on this matter but I would like to take this a little further and actually deprecate them. There are far too many traps and pitfalls and caveats with them that have been ironed out with the new facilities. I just feel it may soon be time to mark them obsolete.

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  • Ubuntu 12.04 version of Netbeans doesn't have the JavaFX plugin

    - by aliasbody
    I just want to know why does Netbeans 7.0.1 from the official Ubuntu 12.04 doesn't have all the plugins (in especial the JavaFX plugin) on it while the official Netbeans from the website (even the version with the less plugin), has it by default ? And how can we change that ? Because I love Ubuntu (even if it is extremly slow on my Asus 1215N (it is the only OS that is slow on it, but that's not very important), but I am trying to use it only with the software provided by the Original repositories without having to download manually or even use any PPA. Thanks in Advance

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  • initial Class design: access modifiers and no-arg constructors

    - by yas
    Context: Student working through Class design in personal/side project for Summer. I've never written anything implemented by others or had to maintain code. Trying to maximize encapsulation and imagining what would make code easy to maintain. Concept: Tight/Loose Class design where Tight and Loose refer to access modifiers and constructors. Tight: initially, everything, including setters, is private and a no-arg constructor is not provided (only a full constructor). Loose: not Tight Exceptions: the obvious like toString Reasoning: If code, at the very beginning, is tight, then it should be guaranteed that changes, with respect to access/creation, should never damage existing implementations. The loosening of code happens incrementally and must be thought through, justified, and safe (validated). Benefit: Existing implementing code should not break if changes are made later. Cost: Takes more time to create. Since this is my own thinking, I hope to get feedback as to whether I should push to work this way. Good idea or bad idea?

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  • Simple rendering produces minor stutter

    - by Ben
    For some reason, this game loop renders the movement of a simple rectangle with no stuttering. double currTime; double prevTime = System.nanoTime() / NANO_TO_SEC; double FPSTIMER = System.nanoTime(); double maxTimeDiff = 100.0 / 1000.0; double delta = 1.0 / 60.0; int processes = 0, frames = 0; while(true){ currTime = System.nanoTime() / NANO_TO_SEC; if(currTime - prevTime > maxTimeDiff) prevTime = currTime; if(currTime >= prevTime){ process(); processes++; prevTime += delta; if(currTime < prevTime){ render(); frames++; } } else{ try{ Thread.sleep((long) (1000 * (prevTime - currTime))); } catch(Exception e){} } if(System.nanoTime() - FPSTIMER > 1000000000.0){ System.out.println("Process: " + (1000 / processes) + "ms FPS: " + (1000 / frames) + "ms"); processes = frames = 0; FPSTIMER += 1000000000.0; } } But for this game loop, I get really minor stuttering where the movement does not look smooth. long prevTime = System.currentTimeMillis(); long prevRenderTime = 0; long currRenderTime = 0; long delta = 0; long msPerTick = 1000 / 60; int frames = 0; int ticks = 0; double FPSTIMER = System.currentTimeMillis(); while (true){ long currTime = System.currentTimeMillis(); delta += (currTime - prevTime) / msPerTick; prevTime = currTime; while (delta >= 1){ ticks++; process(); delta -= 1; } prevRenderTime = System.currentTimeMillis(); render(); frames++; currRenderTime = System.currentTimeMillis(); try{ Thread.sleep((long) ((1000 / FPS) - (currRenderTime - prevRenderTime))); } catch(Exception e){} if(System.currentTimeMillis() - FPSTIMER > 1000.0){ System.out.println("Process: " + (1000.0 / ticks) + "ms FPS: " + (1000.0 / frames) + "ms"); ticks = frames = 0; FPSTIMER += 1000.0; } Is there any critical difference that I'm missing here? The one thing I noticed is that if I uncap the fps for the second game loop, the stuttering goes away. It doesn't make sense to me. Also, the second game loop came from Notch's Minicraft code with just my thread sleeping code added in.

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  • How to determine if a 3D voxel-based room is sealed, efficiently

    - by NigelMan1010
    I've been having some issues with efficiently determining if large rooms are sealed in a voxel-based 3D rooms. I'm at a point where I have tried my hardest to solve the problem without asking for help, but not tried enough to give up, so I'm asking for help. To clarify, sealed being that there are no holes in the room. There are oxygen sealers, which check if the room is sealed, and seal depending on the oxygen input level. Right now, this is how I'm doing it: Starting at the block above the sealer tile (the vent is on the sealer's top face), recursively loop through in all 6 adjacent directions If the adjacent tile is a full, non-vacuum tile, continue through the loop If the adjacent tile is not full, or is a vacuum tile, check if it's adjacent blocks are, recursively. Each time a tile is checked, decrement a counter If the count hits zero, if the last block is adjacent to a vacuum tile, return that the area is unsealed If the count hits zero and the last block is not a vacuum tile, or the recursive loop ends (no vacuum tiles left) before the counter is zero, the area is sealed If the area is not sealed, run the loop again with some changes: Checking adjacent blocks for "breathable air" tile instead of a vacuum tile Instead of using a decrementing counter, continue until no adjacent "breathable air" tiles are found. Once loop is finished, set each checked block to a vacuum tile. Here's the code I'm using: http://pastebin.com/NimyKncC The problem: I'm running this check every 3 seconds, sometimes a sealer will have to loop through hundreds of blocks, and a large world with many oxygen sealers, these multiple recursive loops every few seconds can be very hard on the CPU. I was wondering if anyone with more experience with optimization can give me a hand, or at least point me in the right direction. Thanks a bunch.

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  • How to fire a bullet in a specific direction?

    - by Mike
    I am developing an Android game. I have problem with bullet firing. It's a space ship that has to fire bullets but right now it's firing in a random direction. I have to fire a bullet to the enemy from the only one point on the nose of the ship. Right now the bullets fire sometimes from the tailpart or other. So that's a problem. How do I give a bullet direction and how to fire it from only the head of my space ship?

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  • Making an efficient collision detection system

    - by Sri Harsha Chilakapati
    I'm very new to game development (just started 3 months ago) and I'm learning through creating a game engine. It's located here. In terms of collision, I know only brute-force detection, in which case, the game slows down if there are a number of objects. So my question is How should I program the collisions? I want them to happen automatically for every object and call the object's collision(GObject other) method on each collision. Are there any new algorithms which can make this fast? If so, can anybody shed some light on this topic?

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  • Android From Local DB (DAO) to Server sync (JSON) - Design issue

    - by Taiko
    I sync data between my local DB and a Server. I'm looking for the cleanest way to modelise all of this. I have a com.something.db package That contains a Data Helper and couple of DAO classes that represents objects stored in the db (I didn't write that part) com.something.db --public DataHelper --public Employee @DatabaseField e.g. "name" will be an actual column name in the DB -name @DatabaseField -salary etc... (all in all 50 fields) I have a com.something.sync package That contains all the implementation detail on how to send data to the server. It boils down to a ConnectionManager that is fed by different classes that implements a 'Request' interface com.something.sync --public interface ConnectionManager --package ConnectionManagerImpl --public interface Request --package LoginRequest --package GetEmployeesRequest My issue is, at some point in the sync process, I have to JSONise and de-JSONise my data (E.g. the Employee class). But I really don't feel like having the same Employee class be responsible for both his JSONisation and his actual representation inside the local database. It really doesn't feel right, because I carefully decoupled the rest, I am only stuck on this JSON thing. What should I do ? Should I write 3 Employee classes ? EmployeeDB @DatabaseField e.g. "name" will be an actual column name in the DB -name @DatabaseField -salary -etc... 50 fields EmployeeInterface -getName -getSalary -etc... 50 fields EmployeeJSON -JSON_KEY_NAME = "name" The JSON key happens to be the same as the table name, but it isn't requirement -name -JSON_KEY_SALARY = "salary" -salary -etc... 50 fields It feels like a lot of duplicates. Is there a common pattern I can use there ?

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  • WebFX: Running JavaFX as web page

    - by Bruno.Borges
    This weekend I wanted to learn JavaFX, so I decided to code an idea I had a few years ago when I first saw JavaFX Script. So I started coding a web browser that runs HTML with the awesome, HTML5 supported WebView. But this browser also offers one extra feature: it loads FXML files as if they were HTML. So instead of defining your web page with HTML and running with WebKit, you can define a web page with FXML+CSS+JS and run as a JavaFX application. The project is called WebFX and already has a prototype on GitHub. I also uploaded a video on YouTube demonstrating the idea. What do you think about using JavaFX in the future for web pages, instead of HTML?

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  • Multiple enemy array in LibGDX

    - by johnny-b
    I am trying to make a multiple enemy array, where every 30 secods a new bullet comes from a random point. And if the bullet is clicked it should disapear and a pop like an explosion should appear. And if the bullet hits the ball then the ball pops. so the bullet should change to a different sprite or texture. same with the ball pop. But all that happens is the bullet if touched pops and nothing else happens. And if modified then the bullet keeps flashing as the update is way too much. I have added COMMENTS in the code to explain more on the issues. below is the code. if more code is needed i will provide. Thank you public class GameRenderer { private GameWorld myWorld; private OrthographicCamera cam; private ShapeRenderer shapeRenderer; private SpriteBatch batcher; // Game Objects private Ball ball; private ScrollHandler scroller; private Background background; private Bullet bullet1; private BulletPop bPop; private Array<Bullet> bullets; // This is for the delay of the bullet coming one by one every 30 seconds. /** The time of the last shot fired, we set it to the current time in nano when the object is first created */ double lastShot = TimeUtils.nanoTime(); /** Convert 30 seconds into nano seconds, so 30,000 milli = 30 seconds */ double shotFreq = TimeUtils.millisToNanos(30000); // Game Assets private TextureRegion bg, bPop; private Animation bulletAnimation, ballAnimation; private Animation ballPopAnimation; public GameRenderer(GameWorld world) { myWorld = world; cam = new OrthographicCamera(); cam.setToOrtho(true, 480, 320); batcher = new SpriteBatch(); // Attach batcher to camera batcher.setProjectionMatrix(cam.combined); shapeRenderer = new ShapeRenderer(); shapeRenderer.setProjectionMatrix(cam.combined); // This is suppose to produce 10 bullets at random places on the background. bullets = new Array<Bullet>(); Bullet bullet = null; float bulletX = 00.0f; float bulletY = 00.0f; for (int i = 0; i < 10; i++) { bulletX = MathUtils.random(-10, 10); bulletY = MathUtils.random(-10, 10); bullet = new Bullet(bulletX, bulletY); AssetLoader.bullet1.flip(true, false); AssetLoader.bullet2.flip(true, false); bullets.add(bullet); } // Call helper methods to initialize instance variables initGameObjects(); initAssets(); } private void initGameObjects() { ball = GameWorld.getBall(); bullet1 = myWorld.getBullet1(); bPop = myWorld.getBulletPop(); scroller = myWorld.getScroller(); } private void initAssets() { bg = AssetLoader.bg; ballAnimation = AssetLoader.ballAnimation; bullet1Animation = AssetLoader.bullet1Animation; ballPopAnimation = AssetLoader.ballPopAnimation; } // This is to take the bullet away when clicked or touched. public void onClick() { for (int i = 0; i < bullets.size; i++) { if (bullets.get(i).getBounds().contains(0, 0)) bullets.removeIndex(i); } } private void drawBackground() { batcher.draw(bg1, background.getX(), background.getY(), background.getWidth(), backgroundMove.getHeight()); } public void render(float runTime) { Gdx.gl.glClearColor(0, 0, 0, 1); Gdx.gl.glClear(GL30.GL_COLOR_BUFFER_BIT); batcher.begin(); // Disable transparency // This is good for performance when drawing images that do not require // transparency. batcher.disableBlending(); drawBackground(); batcher.enableBlending(); // when the bullet hits the ball, it should be disposed or taken away and a ball pop sprite/texture should be put in its place if (bullet1.collides(ball)) { // draws the bPop texture but the bullet does not go just keeps going around, and the bPop texture goes. batcher.draw(AssetLoader.bPop, 195, 273); } batcher.draw(AssetLoader.ballAnimation.getKeyFrame(runTime), ball.getX(), ball.getY(), ball.getWidth(), ball.getHeight()); // this is where i am trying to make the bullets come one by one, and if removed via the onClick() then bPop animation // should play but does not??? if(TimeUtils.nanoTime() - lastShot > shotFreq){ // Create your stuff for (int i = 0; i < bullets.size; i++) { bullets.get(i); batcher.draw(AssetLoader.bullet1Animation.getKeyFrame(runTime), bullet1.getX(), bullet1.getY(), bullet1.getOriginX(), bullet1.getOriginY(), bullet1.getWidth(), bullet1.getHeight(), 1.0f, 1.0f, bullet1.getRotation()); if (bullets.removeValue(bullet1, false)) { batcher.draw(AssetLoader.ballPopAnimation.getKeyFrame(runTime), bPop1.getX(), bPop1.getY(), bPop1.getWidth(), bPop1.getHeight()); } } /* Very important to set the last shot to now, or it will mess up and go full auto */ lastShot = TimeUtils.nanoTime(); } // End SpriteBatch batcher.end(); } } Thank you

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  • Pause and Resume and get the value of a countdown timer by savedInstanceState [closed]

    - by Catherine grace Balauro
    I have developed a countdown timer and I am not sure how to pause and resume the timer as the TextView for the timer is being clicked. Click to start then click again to pause and to resume, click again the timer's text view. This is my code: Timer = (TextView)this.findViewById(R.id.time); //TIMER Timer.setOnClickListener(TimerClickListener); counter = new MyCount(600000, 1000); }//end of create private OnClickListener TimerClickListener = new OnClickListener() { public void onClick(View v) { updateTimeTask(); } private void updateTimeTask() { if (decision==0){ counter.start(); decision=1;} else if(decision==2){ counter.onResume1(); decision=1; } else{ counter.onPause1(); decision=2; }//end if }; }; class MyCount extends CountDownTimer { public MyCount(long millisInFuture, long countDownInterval) { super(millisInFuture, countDownInterval); }//MyCount public void onResume1(){ onResume(); } public void onPause1() { onPause();} public void onFinish() { Timer.setText("00:00"); p1++; if (p1<=4){ TextView PScore = (TextView) findViewById(R.id.pscore); PScore.setText(p1 + ""); }//end if }//finish public void onTick(long millisUntilFinished) { Integer milisec = new Integer(new Double(millisUntilFinished).intValue()); Integer cd_secs = milisec / 1000; Integer minutes = (cd_secs % 3600) / 60; Integer seconds = (cd_secs % 3600) % 60; Timer.setText(String.format("%02d", minutes) + ":" + String.format("%02d", seconds)); //long timeLeft = millisUntilFinished / 1000; }//on tick }//class MyCount protected void onResume() { super.onResume(); //handler.removeCallbacks(updateTimeTask); //handler.postDelayed(updateTimeTask, 1000); }//onResume @Override protected void onPause() { super.onPause(); //do stuff }//onPause I am only beginner in android programming and I don't know how to get the value of the countdown timer using savedInstanceState. How do I do this?

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  • I've been told that Exceptions should only be used in exceptional cases. How do I know if my case is exceptional?

    - by tieTYT
    My specific case here is that the user can pass in a string into the application, the application parses it and assigns it to structured objects. Sometimes the user may type in something invalid. For example, their input may describe a person but they may say their age is "apple". Correct behavior in that case is roll back the transaction and to tell the user an error occurred and they'll have to try again. There may be a requirement to report on every error we can find in the input, not just the first. In this case, I argued we should throw an exception. He disagreed, saying, "Exceptions should be exceptional: It's expected that the user may input invalid data, so this isn't an exceptional case" I didn't really know how to argue that point, because by definition of the word, he seems to be right. But, it's my understanding that this is why Exceptions were invented in the first place. It used to be you had to inspect the result to see if an error occurred. If you failed to check, bad things could happen without you noticing. Without exceptions every level of the stack needs to check the result of the methods they call and if a programmer forgets to check in one of these levels, the code could accidentally proceed and save invalid data (for example). Seems more error prone that way. Anyway, feel free to correct anything I've said here. My main question is if someone says Exceptions should be exceptional, how do I know if my case is exceptional?

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  • I am trying to figure out the best way to understand how to cache domain objects

    - by Brett Ryan
    I've always done this wrong, I'm sure a lot of others have too, hold a reference via a map and write through to DB etc.. I need to do this right, and I just don't know how to go about it. I know how I want my objects to be cached but not sure on how to achieve it. What complicates things is that I need to do this for a legacy system where the DB can change without notice to my application. So in the context of a web application, let's say I have a WidgetService which has several methods: Widget getWidget(); Collection<Widget> getAllWidgets(); Collection<Widget> getWidgetsByCategory(String categoryCode); Collection<Widget> getWidgetsByContainer(Integer parentContainer); Collection<Widget> getWidgetsByStatus(String status); Given this, I could decide to cache by method signature, i.e. getWidgetsByCategory("AA") would have a single cache entry, or I could cache widgets individually, which would be difficult I believe; OR, a call to any method would then first cache ALL widgets with a call to getAllWidgets() but getAllWidgets() would produce caches that match all the keys for the other method invocations. For example, take the following untested theoretical code. Collection<Widget> getAllWidgets() { Entity entity = cache.get("ALL_WIDGETS"); Collection<Widget> res; if (entity == null) { res = loadCache(); } else { res = (Collection<Widget>) entity.getValue(); } return res } Collection<Widget> loadCache() { // Get widgets from underlying DB Collection<Widget> res = db.getAllWidgets(); cache.put("ALL_WIDGETS", res); Map<String, List<Widget>> byCat = new HashMap<>(); for (Widget w : res) { // cache by different types of method calls, i.e. by category if (!byCat.containsKey(widget.getCategory()) { byCat.put(widget.getCategory(), new ArrayList<Widget>); } byCat.get(widget.getCatgory(), widget); } cacheCategories(byCat); return res; } Collection<Widget> getWidgetsByCategory(String categoryCode) { CategoryCacheKey key = new CategoryCacheKey(categoryCode); Entity ent = cache.get(key); if (entity == null) { loadCache(); } ent = cache.get(key); return ent == null ? Collections.emptyList() : (Collection<Widget>)ent.getValue(); } NOTE: I have not worked with a cache manager, the above code illustrates cache as some object that may hold caches by key/value pairs, though it's not modelled on any specific implementation. Using this I have the benefit of being able to cache all objects in the different ways they will be called with only single objects on the heap, whereas if I were to cache the method call invocation via say Spring It would (I believe) cache multiple copies of the objects. I really wish to try and understand the best ways to cache domain objects before I go down the wrong path and make it harder for myself later. I have read the documentation on the Ehcache website and found various articles of interest, but nothing to give a good solid technique. Since I'm working with an ERP system, some DB calls are very complicated, not that the DB is slow, but the business representation of the domain objects makes it very clumsy, coupled with the fact that there are actually 11 different DB's where information can be contained that this application is consolidating in a single view, this makes caching quite important.

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  • Regex to String generation

    - by Mifmif
    Let's say that we have a regex and an index i , if we suppose that the set of string that match our regex are sorted in a lexicographical order, how could we get the i element of this list ? Edit : I added this simple example for more explanation : input : regex="[a-c]{1,2}"; index=4; in this case the ordered list of string that matches this regex contains those elements : a aa ab ac b ba bb bc c ca cb cc output : the 4th element which is ac ps: it's known that the string list that match the regex have infinite element, this doesn't have an impact on the proccess of extracting the element in the given index.

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