我已编辑这段代码，将矩形实例化移出onDraw方法。我已在多个设备上进行了测试。
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's screen width.
int screenH; //Devices's 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's position.
if ( (bgrScroll += dBgrY) >= bgrW) {
bgrScroll = 0;
reverseBackroundFirst = !reverseBackroundFirst;
}
//Compute roughly the ball's 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);
}
}
}
}
}
}
如果您注意到了，那么有测量帧率的代码：
now=System.currentTimeMillis();
canvas.drawText(framesCountAvg+" fps", 40, 70, fpsPaint);
framesCount++;
if(now-framesTimer>1000) {
framesTimer=now;
framesCountAvg=framesCount;
framesCount=0;
}
我注意到在我的两个Galaxy Nexus设备上，运行Android 4.0和4.2，帧率约为22-24fps。而在运行Android 2.2的HTC Desire上，则达到了更高的60fps。
同时，您可能还会注意到，在onDraw方法中，我没有分配任何内容。我也没有创建新的Paint对象。但是我真的不明白为什么在我的Galaxy Nexus设备上运行会如此缓慢，有很多卡顿，小球移动得非常缓慢。
请问是否有人知道在Galaxy Nexus上重新绘制存在问题或者有一些设置需要更改？这种情况发生在我的运行4.0和4.2版本的Galaxy Nexus上，所以我不确定它是否与操作系统相关。我已经在开发者选项中关闭了窗口和转换动画效果。无论我是否强制启用2D加速都没有区别。