title: android: difference between ACTION_UP and ACTION_POINTER_UP
body: <p>from the android doc alone i dont really understand the difference between ACTION_UP and ACTION_POINTER_UP.
  <a href="http://developer.android.com/reference/android/view/MotionEvent.html#ACTION_DOWN" rel="noreferrer">http://developer.android.com/reference/android/view/MotionEvent.html#ACTION_DOWN</a></p>
  
  <p>basically i want to capture the event when one finger is released from the screen (even if another one may still be touching it)</p>
  
  <p>thanks!</p>