简单多点测试

public class HorizontalReversePinchDetector { 
 
    public boolean onTouchEvent(MotionEvent e) { 
 
        int pointerCount = e.getPointerCount(); 
 
        if(pointerCount != 2) { 
            Log.d(GESTURE, "not pinching - exactly 2 fingers are needed but have " + pointerCount); 
            clearPinch(); 
            return false; 
        } 
 
        int firstIndex = e.getX(0) < e.getX(1) ? 0: 1; 
        int secondIndex = e.getX(0) < e.getX(1) ? 1: 0; 
 
        Finger currentLeftFinger = new Finger(e.getX(firstIndex), e.getY(firstIndex)); 
        Finger currentRightFinger = new Finger(e.getX(secondIndex), e.getY(secondIndex)); 
 
        float yDifference = Math.abs(currentLeftFinger.getY() - currentRightFinger.getY()); 
        if(yDifference > 80) { 
            Log.d(GESTURE, "not pinching - fingers too vertically-oriented"); 
            clearPinch(); 
            return false; 
        } 
 
        if(initialLeftFinger == null) { 
            initialLeftFinger = currentLeftFinger; 
            initialRightFinger = currentRightFinger; 
            Log.d(GESTURE, "not pinching, but might be starting a pinch..."); 
            return false; 
        } 
 
        float leftFingerDistance = initialLeftFinger.getX() - currentLeftFinger.getX(); 
        float rightFingerDistance = currentRightFinger.getX() - initialRightFinger.getX(); 
 
        float xDistanceBetweenFingers = Math.abs(currentLeftFinger.getX() - currentRightFinger.getX()); 
        if(xDistanceBetweenFingers < minimumDistanceBetweenFingers) { 
            Log.d(GESTURE, "pinching, but fingers are not far enough apart..."); 
            return true; 
        } 
 
        if(leftFingerDistance < minimumDistanceForEachFinger) { 
            Log.d(GESTURE, "pinching, but left finger has not moved enough..."); 
            return true; 
        } 
        if(rightFingerDistance < minimumDistanceForEachFinger) { 
            Log.d(GESTURE, "pinching, but right finger has not moved enough..."); 
            return true; 
        } 
 
        pinchCompleted(); 
        return true; 
    } 
 
    private void pinchCompleted() { 
        Log.d(GESTURE, "pinch completed"); 
        if(pinchListener != null) pinchListener.onPinch(); 
        clearPinch(); 
    } 
 
    public static interface OnPinchListener { 
        void onPinch(); 
    } 
 
    private void clearPinch() { 
        initialLeftFinger = null; 
        initialRightFinger = null; 
    } 
 
    public void setPinchListener(OnPinchListener pinchListener) { 
        this.pinchListener = pinchListener; 
    } 
 
    private static class Finger { 
 
        private Finger(float x, float y) { 
            this.x = x; 
            this.y = y; 
        } 
 
        public float getX() { 
            return x; 
        } 
 
        public float getY() { 
            return y; 
        } 
 
        private float x; 
        private float y; 
    } 
 
    private Finger initialLeftFinger; 
    private Finger initialRightFinger; 
    private OnPinchListener pinchListener; 
    private static final float minimumDistanceForEachFinger = 30; 
    private static final float minimumDistanceBetweenFingers = 50; 
}