onDragCancel method

void onDragCancel()

Implementation

void onDragCancel() {
  // _hold might be null if the drag started.
  // _drag might be null if the drag activity ended and called _disposeDrag.
  assert(_hold == null || _drag == null);
  _hold?.cancel();
  _drag?.cancel();
  assert(_hold == null);
  assert(_drag == null);
}