GestureRecognizer cleanup

Contents

Summary

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

Context

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.

Description of change

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

Migration guide

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);
  }
}

Timeline

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

References

API documentation:

Relevant PRs: