When does onTapCancel in GestureDetector gets called?

December 4, 2021

We use GestureDetector’s onTap every day, but when does onTapCancel gets called?

I read the implemention code, and noticed that onTapCancel comment:

  /// 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;

Still can’t figure out a scenary onTapCancel gets called, can anyone give me an example? Thanks in adavance 🙂

>Solution :

It is typically called when the tap that caused onTapDown will not cause onTapUp. For instance, you press down on a GestureDetector, but then move your finger away from it, and let go.