GestureRecognizer cleanup

OneSequenceGestureRecognizer.addAllowedPointer() was changed to take a PointerDownEvent, like its superclass. Previously, it accepted the more general PointerEvent type, which was incorrect.

The framework only ever passes PointerDownEvent objects to addAllowedPointer(). Declaring OneSequenceGestureRecognizer.addAllowedPointer() to take the more general type was confusing, and caused OneSequenceGestureRecognizer subclasses to have to cast their argument to the right class.

The previous declaration forced OneSequenceGestureRecognizer descendants to override addAllowedPointer() like so:

class CustomGestureRecognizer extends ScaleGestureRecognizer {
  @override
  void addAllowedPointer(PointerEvent event) {
    // insert custom handling of event here...
    super.addAllowedPointer(event);
  }
}

The new method declaration will cause this code to fail with the following error message:

super.addAllowedPointer(event); The argument type 'PointerEvent' can't be assigned to the parameter type 'PointerDownEvent'.
                                #argument_type_not_assignable

Code before migration:

class CustomGestureRecognizer extends ScaleGestureRecognizer {
  @override
  void addAllowedPointer(PointerEvent event) {
    // insert custom handling of event here...
    super.addAllowedPointer(event);
  }
}

Code after migration:

class CustomGestureRecognizer extends ScaleGestureRecognizer {
  @override
  void addAllowedPointer(PointerDownEvent event) {
    // insert custom handling of event here...
    super.addAllowedPointer(event);
  }
}

Landed in version: 2.3.0-13.0.pre
In stable release: 2.5

API documentation:

• OneSequenceGestureRecognizer

Relevant PR:

• Fix addAllowedPointer() overrides

除非另有说明，本文档之所提及适用于 Flutter 的最新稳定版本，本页面最后更新时间: 2024-04-04。 查看文档源码 或者 为本页面内容提出建议。