Android实现图片点击爆炸效果

public class Ball {
 
 public int color; //图片像素点颜色值
 public float x; //粒子圆心坐标x
 public float y; //粒子圆心坐标y
 public float r; //粒子半径
 
 public float vX;//粒子运动水平方向速度
 public float vY;//粒子运动垂直方向速度
 public float aX;//粒子运动水平方向加速度
 public float aY;//粒子运动垂直方向加速度
}

private void init() {
 mPaint = new Paint();
 mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.cat);
 
 for (int i = 0; i < mBitmap.getWidth(); i++) {
  for (int j = 0; j < mBitmap.getHeight(); j++) {
  Ball ball = new Ball();
  ball.color = mBitmap.getPixel(i,j);
  ball.x = i * d + (d/2);
  ball.y = j * d + (d/2);
  ball.r = d/2;
 
  //速度(-20,20)
  ball.vX = (float) (Math.pow(-1, Math.ceil(Math.random() * 1000)) * 20 * Math.random());
  ball.vY = rangInt(-15, 35);
 
  //加速度
  ball.aX = 0;
  ball.aY = 0.98f;
 
  mBalls.add(ball);
  }
 }
 
 mAnimator = ValueAnimator.ofFloat(0,1);
 mAnimator.setRepeatCount(-1);
 mAnimator.setDuration(2000);
 mAnimator.setInterpolator(new LinearInterpolator());
 mAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
  @Override
  public void onAnimationUpdate(ValueAnimator animation) {
  updateBall();
  invalidate();
  }
 });
 }

private void updateBall() {
 for (Ball ball:mBalls) {
  ball.x += ball.vX;
  ball.y += ball.vY;
 
  ball.vX += ball.aX;
  ball.vY += ball.aY;
 }
 }

protected void onDraw(Canvas canvas) {
 super.onDraw(canvas);
 
 canvas.translate(250,250);
 for (Ball ball:mBalls) {
  mPaint.setColor(ball.color);
  canvas.drawCircle(ball.x, ball.y, ball.r, mPaint);
 }
 }

public boolean onTouchEvent(MotionEvent event) {
 if (event.getAction() == MotionEvent.ACTION_DOWN){
  //执行动画
  mAnimator.start();
 }
 return super.onTouchEvent(event);
 }