我们每天都使用手势检测器的onTap，但是onTap取消什么时候被调用呢？
我阅读了实现代码，并注意到onTapCancel注解：

/// 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;

还是想不出TapCancel被调用时的场景，有人能给予我举个例子吗？