Your view needs to implement the onTouchEvent() method, and that method needs to pass the event along to the onTouchEvent() method of the GestureDetector object.
@Override
public boolean onTouchEvent(MotionEvent event)
{
Log.v(DEBUG_TAG,"OnTouchEvent !!!");
boolean result = gestureScanner.onTouchEvent(event);//return the double tap events
return result;
}