何时调用GestureDetector中的OnTaCancel?

我们每天都使用GestureDetector的onTap,但什么时候会调用ONTACancel?

我阅读了实现代码,注意到OnTaCancel评论:

  /// The pointer that previously triggered [onTapDown] will not end up causing
  /// a tap.
  ///
  /// This is called after [onTapDown], and instead of [onTapUp] and [onTap], if
  /// the tap gesture did not win.
  ///
  /// See also:
  ///
  ///  * [kPrimaryButton], the button this callback responds to.
  final GestureTapCancelCallback? onTapCancel;

我还是搞不懂一个叫“风景”的onTapCancel,有人能给我举个例子吗?非常感谢:)