如何为ImageView设置捏合

Question

我有imageView。我使用MotionEvent移动我的ImageView。如何为imageView设置缩放缩放功能。我没有使用任何GestureDetection功能。我需要用两根手指进行简单的捏合。

代码：

imageView.setOnTouchListener(new View.OnTouchListener() {

    @Override
    public boolean onTouch(View v,MotionEvent event) {
        // TODO Auto-generated method stub
        layoutParams = (RelativeLayout.LayoutParams) imageView.getLayoutParams();

            switch(event.getAction())
             {
              case MotionEvent.ACTION_DOWN :
     {
    parms = (RelativeLayout.LayoutParams) imageView.getLayoutParams();


      dx = event.getRawX() - parms.leftMargin;
  dy = event.getRawY() - parms.topMargin;
        }
 break;
case MotionEvent.ACTION_MOVE :
    {
 x = event.getRawX();
 y = event.getRawY();
parms.leftMargin = (int) (x-dx);
    parms.topMargin = (int) (y - dy);
                                    imageView.setLayoutParams(parms);
     }
     break;
    case MotionEvent.ACTION_UP :
    {


 }
    break;
 }

 return false;
}
});

    }

        });