如何在android flip动画中为图像视图添加触摸放大功能

public class ZoomableImageView extends ImageView implements View.OnTouchListener {
    private static final int INVALID_POINTER_ID = -1;

    private float mLastTouchX;
    private float mLastTouchY;
    private int mActivePointerId = INVALID_POINTER_ID;
    private ScaleGestureDetector mScaleDetector;
    private float mScaleFactor = 1.f;

    public ZoomableImageView(Context context) {
        super(context);
        init(context);
    }

    public ZoomableImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(context);
    }

    private void init(Context context) {
        mScaleDetector = new ScaleGestureDetector(context, new ScaleListener());
        setOnTouchListener(this);
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        mScaleDetector.onTouchEvent(event);

        final int action = event.getAction();
        switch (action & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN: {
                final float x = event.getX();
                final float y = event.getY();

                mLastTouchX = x;
                mLastTouchY = y;
                mActivePointerId = event.getPointerId(0);
                break;
            }

            case MotionEvent.ACTION_MOVE: {
                final int pointerIndex = event.findPointerIndex(mActivePointerId);
                final float x = event.getX(pointerIndex);
                final float y = event.getY(pointerIndex);

                final float dx = x - mLastTouchX;
                final float dy = y - mLastTouchY;

                // 移动图像视图
                setTranslationX(getTranslationX() + dx);
                setTranslationY(getTranslationY() + dy);

                mLastTouchX = x;
                mLastTouchY = y;

                break;
            }

            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_CANCEL: {
                mActivePointerId = INVALID_POINTER_ID;
                break;
            }

            case MotionEvent.ACTION_POINTER_UP: {
                final int pointerIndex = (action & MotionEvent.ACTION_POINTER_INDEX_MASK)
                        >> MotionEvent.ACTION_POINTER_INDEX_SHIFT;
                final int pointerId = event.getPointerId(pointerIndex);
                if (pointerId == mActivePointerId) {
                    // 当前活动的指针抬起时，切换到另一个指针
                    final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
                    mLastTouchX = event.getX(newPointerIndex);
                    mLastTouchY = event.getY(newPointerIndex);
                    mActivePointerId = event.getPointerId(newPointerIndex);
                }
                break;
            }
        }

        return true;
    }

    private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
        @Override
        public boolean onScale(ScaleGestureDetector detector) {
            mScaleFactor *= detector.getScaleFactor();
            mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 10.0f));

            // 缩放图像视图
            setScaleX(mScaleFactor);
            setScaleY(mScaleFactor);

            return true;
        }
    }
}

<com.example.ZoomableImageView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:src="@drawable/image" />