1. override
void rejectGesture(int pointer)

Called when this member loses the arena for the given pointer id.

Source 

@override
void rejectGesture(int pointer) {
  super.rejectGesture(pointer);
  if (pointer == primaryPointer) {
    assert(state == GestureRecognizerState.defunct);
    if (onTapCancel != null)
      invokeCallback/*<Null>*/('onTapCancel', onTapCancel); // ignore: STRONG_MODE_INVALID_CAST_FUNCTION_EXPR, https://github.com/dart-lang/sdk/issues/27504
    _reset();
  }
}