onListen property
The callback which is called when the stream is listened to.
May be set to null, in which case no callback will happen.
Implementation
@override
ControllerCallback? get onListen => _controller.onListen;The callback which is called when the stream is listened to.
May be set to null, in which case no callback will happen.
Implementation
@override
set onListen(void Function()? onListenHandler) {
  _controller.onListen = onListenHandler;
}