handleNonAllowedPointer method
- PointerDownEvent event
 
override
    Handles a pointer being added that's not allowed by this recognizer.
Subclasses can override this method and reject the gesture.
See:
Implementation
@override
void handleNonAllowedPointer(PointerDownEvent event) {
  if (!_gestureAccepted) {
    super.handleNonAllowedPointer(event);
  }
}