我正在听FirebaseMessaging.onMessage。print语句按预期工作，但我想添加RemoteMessage的streamController不工作。

FirebaseMessaging.onMessage.listen((message) {
    _streamController.add(message);
    print(message.notification?.body ?? 'empty body'); // working perfectly
        });

这里是streamcontroller

final StreamController<RemoteMessage> _streamController = StreamController();

  Stream<RemoteMessage> notificationStream() {
    return _streamController.stream;
  }

这是我听流的地方：

class _HomePageState extends State<HomePage> {
  late Stream<RemoteMessage> _stream;
  @override
  void initState() {
    _stream = NotificationService().notificationStream();
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Home'),
      ),
      body: StreamBuilder(
        stream: _stream,
        builder: (context, snapshot) {
          if (snapshot.hasData) return Text(snapshot.data!.notification!.body!);
          return const Text('empty snapshot');
        },
      ),
    );
  }
}