Firebase团队删除了Firebase消息传递.configure（）：
原因：configure()的以前实现在多次调用时（注册不同的处理程序或删除处理程序）会导致意外的副作用。此更改允许开发人员更明确地注册和删除处理程序，而不会通过流影响其他人。

使用FirebaseMessaging.onMessage方法获取消息

FirebaseMessaging.onMessage.listen((RemoteMessage message) {
      RemoteNotification notification = message.notification;
      AndroidNotification android = message.notification?.android;
    });

使用FirebaseMessaging.onMessageOpenedApp替换onLaunch和onResume处理程序。

FirebaseMessaging.onMessageOpenedApp.listen((RemoteMessage message) {
      print('A new onMessageOpenedApp event was published!');
      Navigator.pushNamed(context, '/message',
          arguments: MessageArguments(message, true));
    });

请检查以下示例。
https://github.com/FirebaseExtended/flutterfire/blob/master/packages/firebase_messaging/firebase_messaging/example/lib/main.dart

@override
  void initState() {
    super.initState();
    FirebaseMessaging.instance
        .getInitialMessage()
        .then((RemoteMessage message) {
      if (message != null) {
        Navigator.pushNamed(context, '/message',
            arguments: MessageArguments(message, true));
      }
    });

    FirebaseMessaging.onMessage.listen((RemoteMessage message) {
      RemoteNotification notification = message.notification;
      AndroidNotification android = message.notification?.android;

      if (notification != null && android != null) {
        flutterLocalNotificationsPlugin.show(
            notification.hashCode,
            notification.title,
            notification.body,
            NotificationDetails(
              android: AndroidNotificationDetails(
                channel.id,
                channel.name,
                channel.description,
                // TODO add a proper drawable resource to android, for now using
                //      one that already exists in example app.
                icon: 'launch_background',
              ),
            ));
      }
    });

    FirebaseMessaging.onMessageOpenedApp.listen((RemoteMessage message) {
      print('A new onMessageOpenedApp event was published!');
      Navigator.pushNamed(context, '/message',
          arguments: MessageArguments(message, true));
    });
  }

根据Jitesh的回答，对我来说，需要实现getInitialMessage，以便在应用程序终止时（替代onLaunch）使导航工作

// workaround for onLaunch: When the app is completely closed (not in the background) and opened directly from the push notification
    FirebaseMessaging.instance.getInitialMessage().then((RemoteMessage message) {
      print('getInitialMessage data: ${message.data}');
      _serialiseAndNavigate(message);
    });

    // onMessage: When the app is open and it receives a push notification
    FirebaseMessaging.onMessage.listen((RemoteMessage message) {
      print("onMessage data: ${message.data}");
    });

    // replacement for onResume: When the app is in the background and opened directly from the push notification.
    FirebaseMessaging.onMessageOpenedApp.listen((RemoteMessage message) {
      print('onMessageOpenedApp data: ${message.data}');
      _serialiseAndNavigate(message);
    });

更新一个：
***FirebaseMessagingService***对于在应用程序开始时就开始使用非常重要。为此，您需要遵循以下操作：首先声明此函数：

Future<void> _firebaseMessagingBackgroundHandler(RemoteMessage message) async {
  debugPrint("Firebase Messaging firebase is initialized");
  await Firebase.initializeApp();
}

并在app的main（）{}中调用此函数：

FirebaseMessaging.onBackgroundMessage(_firebaseMessagingBackgroundHandler);

然后，您将能够使用以下功能：

FirebaseMessaging.onMessage方法获取消息

FirebaseMessaging.onMessage.listen((RemoteMessage message) {
      RemoteNotification notification = message.notification;
      AndroidNotification android = message.notification?.android;
    });

FirebaseMessaging.onMessageOpenedApp作为onLaunch和onResume处理程序的替代。

FirebaseMessaging.onMessageOpenedApp.listen((RemoteMessage message) {
      print('A new onMessageOpenedApp event was published!');
      Navigator.pushNamed(context, '/message',
          arguments: MessageArguments(message, true));
    });

事件处理：

事件处理经过重新设计，为开发人员提供了更直观的API。基于前台的事件现在可以通过流访问：

FirebaseMessaging.onMessage当Flutter示例在前台时收到传入FCM有效载荷时，返回调用的Stream，其中包含[RemoteMessage]。
FirebaseMessaging.onMessageOpenedApp返回用户按下通过FCM显示的通知时调用的[Stream]。这将替换以前的onLaunch和onResume处理程序。
**FirebaseMessaging.onBackgroundMessage（）**设置应用在后台或终止时触发的后台消息处理程序。IosNotificationSettings：