Android双击放大和缩小列表视图

Question

我使用自定义列表视图来放大和缩小，这是listview：

public class CustomListView extends ListView {

private static final int INVALID_POINTER_ID = -1;
private int mActivePointerId = INVALID_POINTER_ID;
private ScaleGestureDetector mScaleDetector;

private float mScaleFactor = 1.f;
private float maxWidth = 0.0f;
private float maxHeight = 0.0f;
private float mLastTouchX;
private float mLastTouchY;
private float mPosX;
private float mPosY;
private float width;
private float height;

public CustomListView(Context context) {
    super(context);
    mScaleDetector = new ScaleGestureDetector(getContext(),
            new ScaleListener());
}

public CustomListView(Context context, AttributeSet attrs) {
    super(context, attrs);
    mScaleDetector = new ScaleGestureDetector(getContext(),
            new ScaleListener());
}

public CustomListView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    mScaleDetector = new ScaleGestureDetector(getContext(),
            new ScaleListener());
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    width = MeasureSpec.getSize(widthMeasureSpec);
    height = MeasureSpec.getSize(heightMeasureSpec);
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
}

@Override
public boolean onTouchEvent(@NonNull MotionEvent ev) {
    super.onTouchEvent(ev);
    final int action = ev.getAction();
    mScaleDetector.onTouchEvent(ev);
    switch (action & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN: {
            final float x = ev.getX();
            final float y = ev.getY();

            mLastTouchX = x;
            mLastTouchY = y;

            mActivePointerId = ev.getPointerId(0);
            break;
        }

        case MotionEvent.ACTION_MOVE: {
            final int pointerIndex = ev.findPointerIndex(mActivePointerId);
            final float x = ev.getX(pointerIndex);
            final float y = ev.getY(pointerIndex);
            final float dx = x - mLastTouchX;
            final float dy = y - mLastTouchY;

            mPosX += dx;
            mPosY += dy;

            if (mPosX > 0.0f)
                mPosX = 0.0f;
            else if (mPosX < maxWidth)
                mPosX = maxWidth;

            if (mPosY > 0.0f)
                mPosY = 0.0f;
            else if (mPosY < maxHeight)
                mPosY = maxHeight;

            mLastTouchX = x;
            mLastTouchY = y;

            invalidate();
            break;
        }

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

        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 = ev.getPointerId(pointerIndex);
            if (pointerId == mActivePointerId) {
                final int newPointerIndex = pointerIndex == 0 ? 1 : 0;
                mLastTouchX = ev.getX(newPointerIndex);
                mLastTouchY = ev.getY(newPointerIndex);
                mActivePointerId = ev.getPointerId(newPointerIndex);
            }
            break;
        }
    }

    return true;
}

@Override
public void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.save(Canvas.MATRIX_SAVE_FLAG);
    canvas.translate(mPosX, mPosY);
    canvas.scale(mScaleFactor, mScaleFactor);
    canvas.restore();
}

@Override
protected void dispatchDraw(@NonNull Canvas canvas) {
    canvas.save(Canvas.MATRIX_SAVE_FLAG);
    if (mScaleFactor == 1.0f) {
        mPosX = 0.0f;
        mPosY = 0.0f;
    }
    canvas.translate(mPosX, mPosY);
    canvas.scale(mScaleFactor, mScaleFactor);
    super.dispatchDraw(canvas);
    canvas.restore();
    invalidate();
}

private class ScaleListener extends
        ScaleGestureDetector.SimpleOnScaleGestureListener {
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        mScaleFactor *= detector.getScaleFactor();
        mScaleFactor = Math.max(1.0f, Math.min(mScaleFactor, 4.0f));
        maxWidth = width - (width * mScaleFactor);
        maxHeight = height - (height * mScaleFactor);
        invalidate();
        return true;
    }
}

有了这个，listview可以捏合放大和缩小。
我想再做一件事，双击放大，然后再点按两次以缩小列表视图 怎么做？