stream_listen_once.dart

StreamSubscription? subscription;
final eventBus = EventBus();

@override
void initState() {
  super.initState();

  /// initialize subscription
  subscription = eventBus.listenOnce((event) {

    /// check for your event type
    if (event is MyEvent) {
      var data = event.data;
    }
  });
}

/// cancel subscription
@override
void dispose() {
  subscription?.cancel();
  super.dispose();
}

class MyEvent {
  MyData? data;

  MyEvent(this.data);
}

extension EventBusExt<T> on EventBus {
  /// Safely listen messages for ONE TIME ONLY
  StreamSubscription listenOnce(void Function(dynamic event)? onData) {
    return eventBus.streamController.stream.listen(onData);
  }
}