onDecrease property Null safety

VoidCallback? onDecrease

The handler for SemanticsAction.decrease.

This is a request to decrease the value represented by the widget. For example, this action might be recognized by a slider control.

VoiceOver users on iOS can trigger this action by swiping down with one finger. TalkBack users on Android can trigger this action by pressing the volume down button.


VoidCallback? get onDecrease => _onDecrease;
void onDecrease=(VoidCallback? handler)


set onDecrease(VoidCallback? handler) {
  if (_onDecrease == handler)
  final bool hadValue = _onDecrease != null;
  _onDecrease = handler;
  if ((handler != null) != hadValue)