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我想通过使用用户运动事件来旋转图像视图，然后图像必须以减速的角速度继续旋转。我能够使用 ontouchlistener 旋转图像视图。然后我尝试计算视图的速度并将其添加到视图动画中，但不幸的是应用程序在后期崩溃了。此代码中的速度部分不完整，但我不明白如何实现这部分。请帮忙！！！这是我的代码

public class MainActivity extends Activity implements OnTouchListener {

private static Bitmap imageOriginal;
private static Matrix matrix;

private ImageView bottle;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    if (imageOriginal == null) {
        imageOriginal = BitmapFactory.decodeResource(getResources(),
                R.drawable.bottle);
    }

    if (matrix == null) {
        matrix = new Matrix();
    } else {
        matrix.reset();
    }

    bottle = (ImageView) findViewById(R.id.bottle_image);
    bottle.setOnTouchListener(this);

}

private double startAngle, currentAngle;
private VelocityTracker vTracker = null;

@Override
public boolean onTouch(View v, MotionEvent event) {

    switch (event.getActionMasked()) {

    case MotionEvent.ACTION_DOWN:
        if (vTracker == null) {
            vTracker = VelocityTracker.obtain();
        } else {
            vTracker.clear();
        }
        vTracker.addMovement(event);
        startAngle = getAngle(event.getY(), event.getX());
        break;

    case MotionEvent.ACTION_MOVE:
        vTracker.addMovement(event);
        vTracker.computeCurrentVelocity(1000);
        currentAngle = getAngle(event.getY(), event.getX());
        rotateBottle(startAngle, currentAngle);
        startAngle = currentAngle;
        break;

    case MotionEvent.ACTION_UP:
        break;

    }
    return true;
}

private double getAngle(double x1, double y1) {
    double x = x1 - (bottle.getWidth() / 2);
    double y = bottle.getHeight() - y1 - (bottle.getHeight() / 2);
    switch (getQuadrant(x, y)) {
    case 1:
        return Math.asin(y / Math.hypot(x, y)) * 180 / Math.PI;
    case 2:
        return 180 - Math.asin(y / Math.hypot(x, y)) * 180 / Math.PI;
    case 3:
        return 180 + (-1 * Math.asin(y / Math.hypot(x, y)) * 180 / Math.PI);
    case 4:
        return 360 + Math.asin(y / Math.hypot(x, y)) * 180 / Math.PI;
    default:
        return 0;
    }
}

private int getQuadrant(double x, double y) {
    if (x >= 0)
        return y >= 0 ? 1 : 4;
    else
        return y >= 0 ? 2 : 3;
}

private void rotateBottle(double start, double end) {
    final RotateAnimation rotate = new RotateAnimation((float) start,
            (float) end, RotateAnimation.RELATIVE_TO_SELF, 0.5f,
            RotateAnimation.RELATIVE_TO_SELF, 0.5f);
    rotate.setDuration(0);
    rotate.setFillEnabled(true);
    rotate.setFillAfter(true);
    bottle.startAnimation(rotate);
}

}

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