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POAndroid draw using SurfaceView and Thread
 

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  1. POAndroid draw using SurfaceView and Thread
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    <p>I am trying to draw a ball to my screen using 3 classes. I have read a little about this and I found a code snippet that works using the 3 classes on one page, <a href="https://web.archive.org/web/20121204020009/http://www.droidnova.com/playing-with-graphics-in-android-part-ii,160.html" rel="nofollow noreferrer">Playing with graphics in Android</a></p> <p>I altered the code so that I have a ball that is moving and shifts direction when hitting the wall like the picture below <strong>(this is using the code in the link)</strong>.</p> <p><img src="https://i.stack.imgur.com/SPy4V.png" alt="moving ball screenshot"></p> <p>Now I like to separate the classes into 3 different pages for not making everything so crowded, everything is set up the same way.</p> <p><strong>Here are the 3 classes I have.</strong></p> <ol> <li>BallActivity.java</li> <li>Ball.java</li> <li>BallThread.java</li> </ol> <hr> <pre><code>package com.brick.breaker; import android.app.Activity; import android.os.Bundle; import android.view.Window; import android.view.WindowManager; public class BallActivity extends Activity { private Ball ball; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN); ball = new Ball(this); setContentView(ball); } @Override protected void onPause() { super.onPause(); setContentView(null); ball = null; finish(); } } </code></pre> <hr> <pre><code>package com.brick.breaker; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Canvas; import android.view.SurfaceHolder; import android.view.SurfaceView; public class Ball extends SurfaceView implements SurfaceHolder.Callback { private BallThread ballThread = null; private Bitmap bitmap; private float x, y; private float vx, vy; public Ball(Context context) { super(context); bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ball); x = 50.0f; y = 50.0f; vx = 10.0f; vy = 10.0f; getHolder().addCallback(this); ballThread = new BallThread(getHolder(), this); } protected void onDraw(Canvas canvas) { update(canvas); canvas.drawBitmap(bitmap, x, y, null); } public void update(Canvas canvas) { checkCollisions(canvas); x += vx; y += vy; } public void checkCollisions(Canvas canvas) { if(x - vx &lt; 0) { vx = Math.abs(vx); } else if(x + vx &gt; canvas.getWidth() - getBitmapWidth()) { vx = -Math.abs(vx); } if(y - vy &lt; 0) { vy = Math.abs(vy); } else if(y + vy &gt; canvas.getHeight() - getBitmapHeight()) { vy = -Math.abs(vy); } } public int getBitmapWidth() { if(bitmap != null) { return bitmap.getWidth(); } else { return 0; } } public int getBitmapHeight() { if(bitmap != null) { return bitmap.getHeight(); } else { return 0; } } public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { } public void surfaceCreated(SurfaceHolder holder) { ballThread.setRunnable(true); ballThread.start(); } public void surfaceDestroyed(SurfaceHolder holder) { boolean retry = true; ballThread.setRunnable(false); while(retry) { try { ballThread.join(); retry = false; } catch(InterruptedException ie) { //Try again and again and again } break; } ballThread = null; } } </code></pre> <hr> <pre><code>package com.brick.breaker; import android.graphics.Canvas; import android.view.SurfaceHolder; public class BallThread extends Thread { private SurfaceHolder sh; private Ball ball; private Canvas canvas; private boolean run = false; public BallThread(SurfaceHolder _holder,Ball _ball) { sh = _holder; ball = _ball; } public void setRunnable(boolean _run) { run = _run; } public void run() { while(run) { canvas = null; try { canvas = sh.lockCanvas(null); synchronized(sh) { ball.onDraw(canvas); } } finally { if(canvas != null) { sh.unlockCanvasAndPost(canvas); } } } } public Canvas getCanvas() { if(canvas != null) { return canvas; } else { return null; } } } </code></pre> <hr> <p><strong>Here is a picture that shows the outcome of these classes.</strong></p> <p><img src="https://i.stack.imgur.com/FVLXB.png" alt="enter image description here"></p> <p>I've tried to figure this out but since I am pretty new to Android development I thought I could ask for help.</p> <p>Does any one know what is causing the ball to be draw like that? The code is pretty much the same as the one in the link and I have tried to experiment to find a solution but no luck.</p>
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