up method

PointerUpEvent up ({Duration timeStamp: Duration.zero })

Create a PointerUpEvent.

By default, the time stamp on the event is Duration.zero. You can give a specific time stamp by passing the timeStamp argument.

The object is no longer usable after this method has been called.

Implementation 

PointerUpEvent up({ Duration timeStamp = Duration.zero }) {
  assert(isDown);
  _isDown = false;
  return PointerUpEvent(
    timeStamp: timeStamp,
    pointer: pointer,
    position: location
  );
}