Flutter 2.0 with Firebase Cloud Messaging: onMessage not called on Android

Question

I got a problem with Firebase Cloud Messaging onMessage in Flutter 2.0.

The function

FirebaseMessaging.onMessage.listen((RemoteMessage message) { ... }

is not called when receiving a message in the foreground. However, the logs say

broadcast received for message

At the first received message, I get additional warnings, like:

Accessing hidden method Landroid/os/WorkSource

But the warnings disappear on subsequent messages.

The funny thing is, that

FirebaseMessaging.onBackgroundMessage(firebaseMessagingBackgroundHandler);

works.

If I send the app to the background, I get a notification and the defined method is called.

Code

@override
void initState() {
    initializeFlutterFire()
        .then((value) => subscribeToMessages);

    super.initState();
}

Future<void> initializeFlutterFire() async {
    try {
        Firebase.initializeApp();
        setState(() {
            _initialized = true;
            print("Firebase has been initialized");
        });
    } catch (e) {
       setState(() {
           _error = true;
       });
    }
}

void subscribeToMessages() {
    // The following handler is called, when App is in the background.
    FirebaseMessaging.onBackgroundMessage(firebaseMessagingBackgroundHandler);

    // The following function is not called, when a message was received by the device.
    FirebaseMessaging.onMessage.listen((RemoteMessage message) {
        print('Got a message whilst in the foreground!');
        print('Message data: ${message.data}');

        if (message.notification != null) {
            print('Message also contained a notification: ${message.notification}');
        }
    });
}

Future<void> firebaseMessagingBackgroundHandler(RemoteMessage message) async {
    print('message from background handler');
    print("Handling a background message: ${message.messageId}");
}

I got the feeling, that there is no subscription from onMessage().listen(...) and that's why nothing is executed.

Do you have any suggestions, what I am doing wrong?

Thanks in advance, Uwe

Environment

Firebase Console Cloud Messaging

on

Huawei P20 and Samsung Galaxy Tab A 10, both on Android 10.

pubspec.yaml

firebase_core: "^1.0.1"
firebase_messaging: "^9.0.0"

android/build.gradle

dependencies {
    ...
    classpath 'com.google.gms:google-services:4.3.5'

android/app/build.gradle

apply plugin: 'com.android.application'
apply plugin: 'com.google.gms.google-services'
...

android {
    compileSdkVersion 30
    ...
    defaultConfig {
        minSdkVersion 16
        targetSdkVersion 30
        ...

AndroidManifest.xml

<activity ...>
    ...
    <intent-filter>
        <action android:name="FLUTTER_NOTIFICATION_CLICK" />
        <category android:name="android.intent.category.DEFAULT" />
    </intent-filter>
    <intent-filter>
        <action android:name="com.google.firebase.MESSAGING_EVENT"/>
    </intent-filter>
</activity>

flutter doctor

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel beta, 2.0.2, on macOS 11.2.1 20D75 darwin-x64, locale de)
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
[!] Xcode - develop for iOS and macOS
    ✗ Xcode installation is incomplete; a full installation is necessary for iOS development.
    Download at: https://developer.apple.com/xcode/download/
    Or install Xcode via the App Store.
    Once installed, run:
        sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer
        sudo xcodebuild -runFirstLaunch
[✓] Chrome - develop for the web
[✓] Android Studio
[✓] Android Studio (version 4.1)
[✓] IntelliJ IDEA Community Edition (version 2020.1.2)
[✓] VS Code (version 1.53.0)
[✓] Connected device (3 available)

! Doctor found issues in 1 category.

Solution

There is an issue with firebase_messaging 9.0.0 plugin.

If you navigate to the definition of the factory RemoteMessage.fromMap() Using Cmd+Click or Ctrl+Click while hovering over the RemoteMessage class with the mouse), in the return statement, change

contentAvailable: map['contentAvailable'], 
mutableContent: map['mutableContent'],

to

contentAvailable: map['contentAvailable'] ?? false,
to mutableContent: map['mutableContent'] ?? false,

You may have to confirm that you want to modify the package. This should get you through until the package is updated.