我正在尝试设置我的移动的应用程序，以便当用户收到FCM消息时，当他们点击它时，我可以使用消息中的数据将它们路由到适当的屏幕。
我的FCM消息看起来像这样：

const fcmMessage = {
                notification: {
                    title: title,
                    body: message
                },
                data:{
                    type:'Chat',
                    Name: 'Mike',
                    body:'test'
                },
                android: {
                    notification: {
                        title:title,
                        body: message,
                        channel_id:'high_importance_channel'
                    }
                },
                token: msgToken,
            };

然后在我的main（）方法中，我按照下面的代码片段初始化Flutter_Local_notifications。
问题是当我点击通知时，有效负载总是空字符串？这些是执行此操作的代码行。为什么NotificationResponse.payload是空字符串？最终，我需要访问FCM消息中的“data”对象。

void onDidReceiveNotificationResponse(NotificationResponse notificationResponse) async {
  print(notificationResponse.payload);
}

下面是完整的main（）方法。

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();

  // Set the background messaging handler early on, as a named top-level function
  FirebaseMessaging.onBackgroundMessage(_firebaseMessagingBackgroundHandler);

  if (!kIsWeb) {
    channel = const AndroidNotificationChannel(
      'high_importance_channel', // id
      'High Importance Notifications', // title/
      importance: Importance.high,
    );
  }

flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();

var initializationSettingsAndroid =
      AndroidInitializationSettings('@mipmap/ic_launcher');
  var initializationSettingsIOs = DarwinInitializationSettings();
  var initSettings = InitializationSettings(
      android: initializationSettingsAndroid, iOS: initializationSettingsIOs);

  void onDidReceiveNotificationResponse(NotificationResponse notificationResponse) async {
    print(notificationResponse.payload);
}
   
  await flutterLocalNotificationsPlugin.initialize(initSettings,onDidReceiveNotificationResponse: onDidReceiveNotificationResponse,);
            
  /// Create an Android Notification Channel.
  /// We use this channel in the `AndroidManifest.xml` file to override the
  /// default FCM channel to enable heads up notifications.
  await flutterLocalNotificationsPlugin
      .resolvePlatformSpecificImplementation<
          AndroidFlutterLocalNotificationsPlugin>()
      ?.createNotificationChannel(channel);

  await FirebaseMessaging.instance.setForegroundNotificationPresentationOptions(
    alert: true,
    badge: true,
    sound: true,
  );

  FirebaseMessaging.onMessage.listen((RemoteMessage message) {
    print('Got a message whilst in the foreground!');
    print('Message data: ${message.data}');

    if (message.notification != null) {
      RemoteNotification? notification = message.notification;
      AndroidNotification? android = message.notification?.android;
      FlutterLocalNotificationsPlugin s = FlutterLocalNotificationsPlugin();
      s.show(
        notification.hashCode,
        notification?.title,
        notification?.body,
        NotificationDetails(
          android: AndroidNotificationDetails(channel.id, channel.name,
              icon: 'launch_background',
              channelDescription: channel.description,
              importance: Importance.max,
              priority: Priority.high,
              ongoing: true,
              styleInformation: BigTextStyleInformation('')),
        ),
      );
    }
  });

  runApp(MyApp());
}

更新，找到了我需要的。在LocalNotification show方法中，我们可以添加payload属性并将其设置为消息的任何部分。
对于我的用例，我对www.example.com进行编码message.data，然后在didReceive方法中，我可以解码回JSON对象并根据需要使用。

s.show(
        payload: jsonEncode(message.data),
        notification.hashCode,
        notification?.title,
        notification?.body,
        NotificationDetails(
          android: AndroidNotificationDetails(channel.id, channel.name,
              icon: 'launch_background',
              channelDescription: channel.description,
              importance: Importance.max,
              priority: Priority.high,
              ongoing: true,
              styleInformation: BigTextStyleInformation('')),
        ),
      );