I edited this code to migrate Rect instances from the onDraw method. I tested it on several devices.
public class BallBouncesActivity extends Activity { BallBounces ball; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ball = new BallBounces(this); setContentView(ball); } } class BallBounces extends SurfaceView implements SurfaceHolder.Callback { GameThread thread; int screenW; //Device screen width. int screenH; //Devices screen height. int ballX; //Ball x position. int ballY; //Ball y position. int initialY ; float dY; //Ball vertical speed. int ballW; int ballH; int bgrW; int bgrH; int angle; int bgrScroll; int dBgrY; //Background scroll speed. float acc; Bitmap ball, bgr, bgrReverse; boolean reverseBackroundFirst; boolean ballFingerMove; Rect toRect1, fromRect1; Rect toRect2, fromRect2; //Measure frames per second. long now; int framesCount=0; int framesCountAvg=0; long framesTimer=0; Paint fpsPaint=new Paint(); //Frame speed long timeNow; long timePrev = 0; long timePrevFrame = 0; long timeDelta; public BallBounces(Context context) { super(context); ball = BitmapFactory.decodeResource(getResources(), R.drawable.rocket); //Load a ball image. bgr = BitmapFactory.decodeResource(getResources(), R.drawable.sky_bgr); //Load a background. ballW = ball.getWidth(); ballH = ball.getHeight(); toRect1 = new Rect(0, 0, bgr.getWidth(), bgr.getHeight()); fromRect1 = new Rect(0, 0, bgr.getWidth(), bgr.getHeight()); toRect2 = new Rect(0, 0, bgr.getWidth(), bgr.getHeight()); fromRect2 = new Rect(0, 0, bgr.getWidth(), bgr.getHeight()); //Create a flag for the onDraw method to alternate background with its mirror image. reverseBackroundFirst = false; //Initialise animation variables. acc = 0.2f; //Acceleration dY = 0; //vertical speed initialY = 100; //Initial vertical position angle = 0; //Start value for the rotation angle bgrScroll = 0; //Background scroll position dBgrY = 1; //Scrolling background speed fpsPaint.setTextSize(30); //Set thread getHolder().addCallback(this); setFocusable(true); } @Override public void onSizeChanged (int w, int h, int oldw, int oldh) { super.onSizeChanged(w, h, oldw, oldh); //This event-method provides the real dimensions of this custom view. screenW = w; screenH = h; bgr = Bitmap.createScaledBitmap(bgr, w, h, true); //Scale background to fit the screen. bgrW = bgr.getWidth(); bgrH = bgr.getHeight(); //Create a mirror image of the background (horizontal flip) - for a more circular background. Matrix matrix = new Matrix(); //Like a frame or mould for an image. matrix.setScale(-1, 1); //Horizontal mirror effect. bgrReverse = Bitmap.createBitmap(bgr, 0, 0, bgrW, bgrH, matrix, true); //Create a new mirrored bitmap by applying the matrix. ballX = (int) (screenW /2) - (ballW / 2) ; //Centre ball X into the centre of the screen. ballY = -50; //Centre ball height above the screen. } //*************************************** //************* TOUCH ***************** //*************************************** @Override public synchronized boolean onTouchEvent(MotionEvent ev) { switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: { ballX = (int) ev.getX() - ballW/2; ballY = (int) ev.getY() - ballH/2; ballFingerMove = true; break; } case MotionEvent.ACTION_MOVE: { ballX = (int) ev.getX() - ballW/2; ballY = (int) ev.getY() - ballH/2; break; } case MotionEvent.ACTION_UP: ballFingerMove = false; dY = 0; break; } return true; } @Override public void onDraw(Canvas canvas) { super.onDraw(canvas); //Draw scrolling background. fromRect1.set(0, 0, bgrW - bgrScroll, bgrH); toRect1.set(bgrScroll, 0, bgrW, bgrH); fromRect2.set(bgrW - bgrScroll, 0, bgrW, bgrH); toRect2.set(0, 0, bgrScroll, bgrH); // Rect fromRect1 = new Rect(0, 0, bgrW - bgrScroll, bgrH); // Rect toRect1 = new Rect(bgrScroll, 0, bgrW, bgrH); // // Rect fromRect2 = new Rect(bgrW - bgrScroll, 0, bgrW, bgrH); // Rect toRect2 = new Rect(0, 0, bgrScroll, bgrH); if (!reverseBackroundFirst) { canvas.drawBitmap(bgr, fromRect1, toRect1, null); canvas.drawBitmap(bgrReverse, fromRect2, toRect2, null); } else{ canvas.drawBitmap(bgr, fromRect2, toRect2, null); canvas.drawBitmap(bgrReverse, fromRect1, toRect1, null); } //Next value for the background position. if ( (bgrScroll += dBgrY) >= bgrW) { bgrScroll = 0; reverseBackroundFirst = !reverseBackroundFirst; } //Compute roughly the ball speed and location. if (!ballFingerMove) { ballY += (int) dY; //Increase or decrease vertical position. if (ballY > (screenH - ballH)) { dY=(-1)*dY; //Reverse speed when bottom hit. } dY+= acc; //Increase or decrease speed. } //Increase rotating angle if (angle++ >360) angle =0; //DRAW BALL //Rotate method one /* Matrix matrix = new Matrix(); matrix.postRotate(angle, (ballW / 2), (ballH / 2)); //Rotate it. matrix.postTranslate(ballX, ballY); //Move it into x, y position. canvas.drawBitmap(ball, matrix, null); //Draw the ball with applied matrix. */// Rotate method two canvas.save(); //Save the position of the canvas matrix. canvas.rotate(angle, ballX + (ballW / 2), ballY + (ballH / 2)); //Rotate the canvas matrix. canvas.drawBitmap(ball, ballX, ballY, null); //Draw the ball by applying the canvas rotated matrix. canvas.restore(); //Rotate the canvas matrix back to its saved position - only the ball bitmap was rotated not all canvas. //*/ //Measure frame rate (unit: frames per second). now=System.currentTimeMillis(); canvas.drawText(framesCountAvg+" fps", 40, 70, fpsPaint); framesCount++; if(now-framesTimer>1000) { framesTimer=now; framesCountAvg=framesCount; framesCount=0; } } @Override public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { } @Override public void surfaceCreated(SurfaceHolder holder) { thread = new GameThread(getHolder(), this); thread.setRunning(true); thread.start(); } @Override public void surfaceDestroyed(SurfaceHolder holder) { boolean retry = true; thread.setRunning(false); while (retry) { try { thread.join(); retry = false; } catch (InterruptedException e) { } } } class GameThread extends Thread { private SurfaceHolder surfaceHolder; private BallBounces gameView; private boolean run = false; public GameThread(SurfaceHolder surfaceHolder, BallBounces gameView) { this.surfaceHolder = surfaceHolder; this.gameView = gameView; } public void setRunning(boolean run) { this.run = run; } public SurfaceHolder getSurfaceHolder() { return surfaceHolder; } @Override public void run() { Canvas c; while (run) { c = null; //limit frame rate to max 60fps timeNow = System.currentTimeMillis(); timeDelta = timeNow - timePrevFrame; if ( timeDelta < 16) { try { Thread.sleep(16 - timeDelta); } catch(InterruptedException e) { } } timePrevFrame = System.currentTimeMillis(); try { c = surfaceHolder.lockCanvas(null); synchronized (surfaceHolder) { //call methods to draw and process next fame gameView.onDraw(c); } } finally { if (c != null) { surfaceHolder.unlockCanvasAndPost(c); } } } } } }
If you notice, there is a code for measuring frame rate:
now=System.currentTimeMillis(); canvas.drawText(framesCountAvg+" fps", 40, 70, fpsPaint); framesCount++; if(now-framesTimer>1000) { framesTimer=now; framesCountAvg=framesCount; framesCount=0; }
I see that on both of my Galaxy Nexus devices running Android 4.0 and 4.2, it is 22-24 frames per second. On my HTC Desire running Android 2.2, it looks more like 60 frames per second.
You will also notice that I do not highlight anything in the onDraw method. I also do not create new Paint objects. I really don’t understand how this works, therefore, it is so slower on my Galaxy Nexus devices. There is a lot of stuttering, and the ball moves very slowly.
Does anyone know if there is a setting that I can cancel, or a known issue with re-drawing on the Galaxy Nexus? This happens with my Galaxy Nexus that runs 4.0 and the one that runs 4.2, so I'm not sure if it depends on the OS. I disabled the window and transition animation in the developer settings. Do I affect two-dimensional acceleration.