java.lang.RuntimeException: Unable to create service error when receiving a firebase messaging message

Question

I'm setting up FirebaseMessaging and when I receive the message I do get the prints I setup in the .onMessage callback:

I/flutter (27328): New FCM onMessage message : Instance of 'RemoteMessage' 
I/flutter (27328): 
I/flutter (27328): New FCM onMessage message id: 0:1653641357492638%dad60691dad60691
W/com.xxx.foods(27328): Accessing hidden method Landroid/os/WorkSource;->add(I)Z (unsupported,test-api, reflection, allowed)
I/flutter (27328): New FCM onMessage message sentTime: 2022-05-27 10:49:17.485
W/com.xxx.foods(27328): Accessing hidden method Landroid/os/WorkSource;->add(ILjava/lang/String;)Z (unsupported,test-api, reflection, allowed)
W/com.xxx.foods(27328): Accessing hidden method Landroid/os/WorkSource;->get(I)I (unsupported, reflection, allowed)
W/com.xxx.foods(27328): Accessing hidden method Landroid/os/WorkSource;->getName(I)Ljava/lang/String; (unsupported, reflection, allowed)
I/flutter (27328): New FCM onMessage message notification title: a
I/flutter (27328): New FCM onMessage message notification body: a

but then the app crashes with the error:

D/AndroidRuntime(27328): Shutting down VM E/AndroidRuntime(27328): FATAL EXCEPTION: main E/AndroidRuntime(27328): Process: com.xxx.foods, PID: 27328 E/AndroidRuntime(27328): java.lang.RuntimeException: Unable to create service com.example.xxx.java.MyFirebaseMessagingService: java.lang.ClassNotFoundException: Didn't find class "com.example.xxx.java.MyFirebaseMessagingService" on path: DexPathList[[zip file "/data/app/~~LYrL5kv915DhEfzUSgPwZg==/com.xxx.foods-dIN5_0rsX6Wo-G0jfKtL2Q==/base.apk"],nativeLibraryDirectories=[/data/app/~~LYrL5kv915DhEfzUSgPwZg==/com.xxx.foods-dIN5_0rsX6Wo-G0jfKtL2Q==/lib/arm64, /data/app/~~LYrL5kv915DhEfzUSgPwZg==/com.xxx.foods-dIN5_0rsX6Wo-G0jfKtL2Q==/base.apk!/lib/arm64-v8a, /system/lib64, /system_ext/lib64]] E/AndroidRuntime(27328):  at android.app.ActivityThread.handleCreateService(ActivityThread.java:4619) E/AndroidRuntime(27328):    at android.app.ActivityThread.access$1800(ActivityThread.java:265) E/AndroidRuntime(27328):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2122) E/AndroidRuntime(27328):    at android.os.Handler.dispatchMessage(Handler.java:106) E/AndroidRuntime(27328):    at android.os.Looper.loopOnce(Looper.java:210) E/AndroidRuntime(27328):     at android.os.Looper.loop(Looper.java:299) E/AndroidRuntime(27328):     at android.app.ActivityThread.main(ActivityThread.java:8166) E/AndroidRuntime(27328):   at java.lang.reflect.Method.invoke(Native Method) E/AndroidRuntime(27328):  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:556) E/AndroidRuntime(27328):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1037) E/AndroidRuntime(27328): Caused by: java.lang.ClassNotFoundException: Didn't find class "com.example.xxx.java.MyFirebaseMessagingService" on path: DexPathList[[zip file "/data/app/~~LYrL5kv915DhEfzUSgPwZg==/com.xxx.foods-dIN5_0rsX6Wo-G0jfKtL2Q==/base.apk"],nativeLibraryDirectories=[/data/app/~~LYrL5kv915DhEfzUSgPwZg==/com.xxx.foods-dIN5_0rsX6Wo-G0jfKtL2Q==/lib/arm64, /data/app/~~LYrL5kv915DhEfzUSgPwZg==/com.xxx.foods-dIN5_0rsX6Wo-G0jfKtL2Q==/base.apk!/lib/arm64-v8a, /system/lib64, /system_ext/lib64]] E/AndroidRuntime(27328):     at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:218) E/AndroidRuntime(27328):     at java.lang.ClassLoader.loadClass(ClassLoader.java:379) E/AndroidRuntime(27328):   at java.lang.ClassLoader.loadClass(ClassLoader.java:312) E/AndroidRuntime(27328):   at android.app.AppComponentFactory.instantiateService(AppComponentFactory.java:129) E/AndroidRuntime(27328):    at androidx.core.app.CoreComponentFactory.instantiateService(CoreComponentFactory.java:75) E/AndroidRuntime(27328):     at android.app.ActivityThread.handleCreateService(ActivityThread.java:4588) E/AndroidRuntime(27328):    ... 9 more D/OOMEventManagerFK(27328): checkEventAndDumpForJE: 0 I/Process (27328): Sending signal. PID: 27328 SIG: 9 Lost connection to device

In my android/app/main/AndroidManifest.xml I setup a service as described in the docs:

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.xxx">
    <!-- io.flutter.app.FlutterApplication is an android.app.Application that
         calls FlutterMain.startInitialization(this); in its onCreate method.
         In most cases you can leave this as-is, but you if you want to provide
         additional functionality it is fine to subclass or reimplement
         FlutterApplication and put your custom class here. -->

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

    <application
        android:name="io.flutter.app.FlutterApplication"
        android:label="xxx"
        android:icon="@mipmap/ic_launcher">

        <activity
            android:name=".MainActivity"
            android:exported="true"
            android:launchMode="singleTop"
            android:theme="@style/LaunchTheme"
            android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
            android:hardwareAccelerated="true"
            android:windowSoftInputMode="adjustResize">
            <!-- Specifies an Android theme to apply to this Activity as soon as
                 the Android process has started. This theme is visible to the user
                 while the Flutter UI initializes. After that, this theme continues
                 to determine the Window background behind the Flutter UI. -->
            <meta-data
              android:name="io.flutter.embedding.android.NormalTheme"
              android:resource="@style/NormalTheme"
              />
            <!-- Displays an Android View that continues showing the launch screen
                 Drawable until Flutter paints its first frame, then this tutorial
                 screen fades out. A tutorial screen is useful to avoid any visual
                 gap between the end of Android's launch screen and the painting of
                 Flutter's first frame. -->
            <meta-data
              android:name="io.flutter.embedding.android.SplashScreenDrawable"
              android:resource="@drawable/launch_background"
              />
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>
        </activity>
        <service
            android:name=".java.MyFirebaseMessagingService"
            android:exported="false">
            <intent-filter>
                <action android:name="com.google.firebase.MESSAGING_EVENT" />
            </intent-filter>
        </service>

        <!-- Don't delete the meta-data below.
             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
        <meta-data
            android:name="flutterEmbedding"
            android:value="2" />
    </application>
</manifest>

and in MainActivity.kt I setup FlutterFragmentedActivity:

package com.example.xxx

//import io.flutter.embedding.android.FlutterActivity
import io.flutter.embedding.android.FlutterFragmentActivity
import io.flutter.embedding.engine.FlutterEngine
import io.flutter.plugins.GeneratedPluginRegistrant
import androidx.annotation.NonNull;

//class MainActivity: FlutterActivity() {
//}
class MainActivity: FlutterFragmentActivity() {
    override fun configureFlutterEngine(@NonNull flutterEngine: FlutterEngine) {
        GeneratedPluginRegistrant.registerWith(flutterEngine);
    }
}

Is there something else I should setup?

I initialise it like so:

  print('New FCM firebaseMessagingBackgroundHandler message : ${message.toString()} \n\n');
  print('New FCM firebaseMessagingBackgroundHandler message id: ${message.messageId}');
  print('New FCM firebaseMessagingBackgroundHandler message sentTime: ${message.sentTime}');

  print('New FCM firebaseMessagingBackgroundHandler message notification title: ${message.notification.title}');
  print('New FCM firebaseMessagingBackgroundHandler message notification body: ${message.notification.body}');
  await Firebase.initializeApp();
}

void main() async {
  // set the publishable key for Stripe - this is mandatory
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  FirebaseMessaging.onBackgroundMessage(firebaseMessagingBackgroundHandler);

...

but then, as I need to send a Bloc event when receiving a message, I set FirebaseMessaging in the next screen which would have the Bloc available in the tree:

class _ShowSplashScreenWidgetState extends State<ShowSplashScreenWidget> {
  final FirebaseMessaging _firebaseMessaging = FirebaseMessaging.instance;
  String fcmToken;

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

    /// FCM setup

    _firebaseMessaging.requestPermission(sound: true, badge: true, alert: true, provisional: false, carPlay: false, criticalAlert: false);

    _firebaseMessaging.getToken().then((token) {
      print(' _firebaseMessaging.getToken token: $token');

      if (mounted) {
        setState(() {
          fcmToken = token;
        });
      } else {
        fcmToken = token;
      }
    });

    FirebaseMessaging.onMessage.listen((message) {
      print('New FCM onMessage message : ${message.toString()} \n\n');
      print('New FCM onMessage message id: ${message.messageId}');
      print('New FCM onMessage message sentTime: ${message.sentTime}');

      print('New FCM onMessage message notification title: ${message.notification.title}');
      print('New FCM onMessage message notification body: ${message.notification.body}');

      NotificationModel notification = NotificationModel(
          id: message.messageId, read: false, date: message.sentTime, title: message.notification.title, body: message.notification.body);
      // BlocProvider.of<NotificationBloc>(context).add(SaveNotification(notification: notification));
    });

    FirebaseMessaging.onMessageOpenedApp.listen((message) {
      print('New FCM onMessageOpenedApp message : ${message.toString()} \n\n');
      print('New FCM onMessageOpenedApp message id: ${message.messageId}');
      print('New FCM onMessageOpenedApp message sentTime: ${message.sentTime}');

      print('New FCM onMessageOpenedApp message notification title: ${message.notification.title}');
      print('New FCM onMessageOpenedApp message notification body: ${message.notification.body}');
      NotificationModel notification = NotificationModel(
          id: message.messageId, read: false, date: message.sentTime, title: message.notification.title, body: message.notification.body);
      BlocProvider.of<NotificationBloc>(context).add(SaveNotification(notification: notification));
    });

....

Answer 1

Do you have the class java.MyFirebaseMessagingService? plus, in newer versions of FCM, you don't have to initialize a service class neither in your Manifest or your code, simple, remove MyFirebaseMessagingService service tag from your AndroidManifest.xml