shouldDispatchEvent method Null safety

  1. @override
bool shouldDispatchEvent()
override

Whether a key down event, and likewise its accompanying key up event, should be dispatched.

Certain events on some platforms should not be dispatched to listeners according to Flutter's event model. For example, on macOS, Fn keys are skipped to be consistent with other platform. On Win32, events dispatched for IME (VK_PROCESSKEY) are also skipped.

This method will be called upon every down events. By default, this method always return true. Subclasses should override this method to define the filtering rule for the platform. If this method returns false for an event message, the event will not be dispatched to listeners, but respond with "handled: true" immediately. Moreover, the following up event with the same physical key will also be skipped.

Implementation

@override
bool shouldDispatchEvent() {
  // In Win32 API, down events related to IME operations use VK_PROCESSKEY as
  // keyCode. This event, as well as the following key up event (which uses a
  // normal keyCode), should be skipped, because the effect of IME operations
  // will be handled by the text input API.
  return keyCode != _vkProcessKey;
}