How to set pinch for ImageView

Question

I have imageView. I used move my ImageView using MotionEvent. How to set pinch zoom functionality for imageView. I didn't use any GestureDetection functionality. I need simple pinch with two fingers.

code:

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;
}
});

    }

        });