[firebase_messaging] background messaging documentation prob

[mobileink]

Describe the bug
It took me about three hours to figure out why my background message handler wasn't working. The documentation says "Define a top level Dart method to handle background messages." This is confusing, since there are no top level "methods", only top-level functions. Naturally I defined a handler in my class (it works for onMessage, ought to work for onBackgroundMessage, right?) and had to dig through the flutter source to figure out the problem.

To Reproduce
Steps to reproduce the behavior:

1. Define your onBackgroundMessage callback the same way you define your onMessage handler, as a method in the class that calls _firebaseMessaging.configure
2. Result:
   The following NoSuchMethodError was thrown building Builder:
   I/flutter (25669): The method 'toRawHandle' was called on null.
   I/flutter (25669): Receiver: null
   I/flutter (25669): Tried calling: toRawHandle()

Expected behavior

The documentation should be amended to indicate that the handler must be either a top level function, or a static method.

Thanks for the plugin!

Can you be more specific on how exactly you solved the problem. Tried making the handler static and it broke during compile time

[kleinpetr]

I have the same problem. Can you update the documentation? I am confused by this

1. Add an Application.java class to your app (where??)
2. Set name property of application in AndroidManifest.xml (where??, how??)
3. Define a top level Dart method to handle background messages (where?? at the same time when I configured onMessage callback?)

Thank you for help.

[serendipity1004]

Yes I have the same question as @kleinpetr

[mobileink]

On Mon, Sep 23, 2019 at 12:05 PM kleinpetr ***@***.***> wrote: I have the same problem. Can you update the documentation? I am confused by this 1. Add an Application.java class to your app *(where??)* 2. Set name property of application in AndroidManifest.xml *(where??, how??)* 3. Define a top level Dart method to handle background messages *(where?? at the same time when I configured onMessage callback?)* Thank you for help.

Here's what worked for me (with names changed to protect the innocent): In android/app/src/main/AndroidManifest.xml: <application android:name="org.your.app.Application" In android/app/src/main/java/org/your/app/Application.java: package org.your.app; import io.flutter.app.FlutterApplication; import io.flutter.plugin.common.PluginRegistry; import io.flutter.plugin.common.PluginRegistry.PluginRegistrantCallback; import io.flutter.plugins.GeneratedPluginRegistrant; import io.flutter.plugins.firebasemessaging.FlutterFirebaseMessagingService; public class Application extends FlutterApplication implements PluginRegistrantCallback { @OverRide public void onCreate() { super.onCreate(); FlutterFirebaseMessagingService.setPluginRegistrant(this); } @OverRide public void registerWith(PluginRegistry registry) { GeneratedPluginRegistrant.registerWith(registry); } } Note that there is also android/app/src/main/java/org/your/app/MainActivity.java, which is generated by Flutter (I think). In you flutter code (assume main.dart), follow the basic instructions for initializing Firebase etc. from the example at https://github.com/FirebaseExtended/flutterfire/blob/master/packages/firebase_messaging/example/lib/main.dart At the top level (i.e. not within a class definition) add: Future<dynamic> _backgroundMessageHandler(Map<String, dynamic> message) { print("_backgroundMessageHandler"); if (message.containsKey('data')) { // Handle data message final dynamic data = message['data']; print("_backgroundMessageHandler data: ${data}"); } if (message.containsKey('notification')) { // Handle notification message final dynamic notification = message['notification']; print("_backgroundMessageHandler notification: ${notification}"); } I added the "_" prefix to keep this function private to main.dart. It can still be passed to _firebaseMessaging.configure, since it is a named function. You can also define it within the same class in which you call _firebaseMessaging.configure, but ONLY if it is marked static. If it is a non-static method, Flutter (or Dart) will treat it as an anonymous closure, which cannot be used as a callback (a cb must be either a function object or a static method). See the comment in GetCallbackFromHandle in https://github.com/flutter/engine/blob/master/lib/ui/dart_runtime_hooks.cc. Then pass the callback in your call to configure (you also need to provide callbacks to onLaunch and onResume; these can be : _firebaseMessaging.configure( onMessage: myForegroundMessageHandler, onBackgroundMessage: _backgroundMessageHandler, ... The callbacks must have type MessageHandler defined in firebase_messaging.dart in the package: typedef Future<dynamic> MessageHandler(Map<String, dynamic> message); That takes care of the frontend. The backend must also be properly configured, and you must send your message (either a data message or a notification message with a data payload) from your server, not from the FB console. In particular, for notification+data, you must pass "FLUTTER_NOTIFICATION_CLICK" as value for the click_notification key of the android config stanza. Which means you need to set a platform-specific field. The details are at https://firebase.google.com/docs/cloud-messaging/concept-options#when_to_use_platform-specific_fields; sample server code is at https://firebase.google.com/docs/cloud-messaging/send-message#example_notification_message_with_platform-specific_delivery_options but you need to add a call to setClickAction on the AndroidConfig.Builder ( https://firebase.google.com/docs/reference/admin/java/reference/com/google/firebase/messaging/AndroidNotification.Builder.html ) e.g. .setClickAction("FLUTTER_NOTIFICATION_CLICK") HTH, Gregg <

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[kleinpetr]

I can't configure firebase at the main.dart because I have some logic about this. For example I am initing the FCM only if user is logged, etc. So I have to configure firebase inside a class. You said the background callback must be static, OK I set static method, but still not working.

main.dart
initState(){
  ....
  HelperClass.initFCM(some dependencies);
}

helperClass.dart
class HelperClass
{
final FirebaseMessaging _firebaseMessaging = FirebaseMessaging();

  static Future<dynamic> backgroundMessageHandler(Map<String, dynamic> message) {
  print("_backgroundMessageHandler");
  if (message.containsKey('data')) {
    // Handle data message
    final dynamic data = message['data'];
    print("_backgroundMessageHandler data: ${data}");
  }

  if (message.containsKey('notification')) {
    // Handle notification message
    final dynamic notification = message['notification'];
    print("_backgroundMessageHandler notification: ${notification}");
  }

  Future<void> initFCM(...){
    _firebaseMessaging.configure(
      .....,
      onBackgroundMessage: backgroundMessageHandler,
      .....
      );
  }
}

Okay I don't know how I managed to get mine to work honestly. I just followed all the instructions and commented out the onBackgroundMessage because it was giving fatal compile time errors.

firebaseMessaging.configure(
//onBackgroundMessage: _backgroundMessageHandler,

  onMessage: _messageHandler,

  onLaunch: _lauchHandler,

  onResume: _resumeHandler,
);

like that but I'm confused why my _backgroundMessageHander top-level function gets triggered even on app terminated or forground.

I also made sure that all my handlers including message, resume, and launch are top-level functions. (NOT IN ANY CLASS). I hope this helps someone because I've been struggling with this for days.

[mobileink]

On Wed, Sep 25, 2019 at 2:24 AM kleinpetr ***@***.***> wrote: I dont understand the part of AndroidManifest.xml. Can I use MainActivity.java generated by Flutter or rewrite this file by Application.java from tutorial. Or add Application.java within MainActivity.java. But how can I set in AnroidManifest.xml ?? <application android:name="cz.example.myapp.Application"></application> <application android:name="io.flutter.app.FlutterApplication" android:label="MyApp" ***@***.***/ic_launcher"> <!-- <meta-data android:name="com.google.android.geo.API_KEY" android:value="AIzaSyBmpFHEI4rZ7eIenkwaEDYvXGYMxt60yNM"/> --> <activity android:name=".MainActivity" android:launchMode="singleTop" ***@***.***/LaunchTheme" android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode" android:hardwareAccelerated="true" android:windowSoftInputMode="adjustResize"> <!-- disable splashScreen --> <meta-data android:name="io.flutter.app.android.SplashScreenUntilFirstFrame" android:value="false" /> This is not working

We cannot help you with "this is not working." If you can give specifics we can try.

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[kleinpetr]

What do you mean top-level handler? I need working with variables and methods from the class in fcm calbacks.. is there some chance ro declare onBackgroundMessage callback the same way as other callbacks??

[luckycreationsindia]

Please update example of firebase_messaging where it handles background messages. Seriously it's very confusing or anyone please upload demo working project for handling onBackground messages.

[ektelat]

we can't understand this point

[kleinpetr]

@ektelat It means you need to use your custom Application class instead of the default flutter Application class

You have this in manifets (probably)
<application android:name="io.flutter.app.FlutterApplication" android:label="Name app" android:icon="@mipmap/ic_launcher">

And you need replace io.flutter.app.FlutterApplication to your Application class for example com.yourdomain.Application or or .Application (maybe)

[ektelat]

@kleinpetr
i changed it as you told me but the app can't be installed all the time it crashed

stop here....

[kleinpetr]

@ektelat show me your Application.java please

[ektelat]

@kleinpetr i get my mistake, i just copy the same example of flutter document so it's with
package io.flutter.plugins.firebasemessagingexample;
i changed it and it's installing now put after it's loaded unfortinatlly it crash again.
after i removed onBackgroundMessage from messaging configure

it's work now.

so what to do with: onBackgroundMessage i need it

here the myBackgroundMessageHandler:

what is my problem??