[firebase_messaging] iOS is not receiving apns payload and not showing notification when it is in background or killed

[FernandoUFS]

Describe the bug
A couple days ago I notice that my application stopped showing notifications from firebase just on iOS. I send a POST request to https://fcm.googleapis.com/fcm/send containing the payload, when the app is on background nothing happens, when I open the app the method onMessage is executed with few fields shown below.

The notification was working from about 2 months since first implementation, it was shown when the app was in background, my payload was not changed but it stopped working.

Expected Behaviour
Show notification when app is in background or killed (as before)

My request:

My alternative request with same result:

{
    "notification": {
        "title": "Title test",
        "body": "Body message"
    }
    "condition": "'match_1474' in topics"
}

My code for debug:

...
_firebaseMessaging.configure(
      onBackgroundMessage: myBackgroundMessageHandler, //static method printing message (not get called)
      onMessage: (Map<String, dynamic> message) async {
        Log.d("onMessage: ${jsonEncode(message)}");
      }
      onResume: (Map<String, dynamic> message) async {
        Log.d("onResume: ${jsonEncode(message)}");
      },
      onLaunch: (Map<String, dynamic> message) async {
        Log.d("onLaunch: ${jsonEncode(message)}");
      }
);
...

The console:
This message is print only when I receive the notification with app open or when I open the app after receive with app closed.

flutter: onMessage: {"collapse_key":"4cH4++Z1SUoDiUf9+l9DKFX/sc=","from":"50068760310"}

Additional context
I use AdminSDK for PHP for real use and the payload includes android specific data, but I tested on Postman to make sure the problem is not there.

The problem is occurring on production with all users I have checked (TestFlight Beta).
On Android it is working as expected.

If I send just data the app continues receiving only when the app is on foreground.
Example

{
    "data": {
        "title": "Title test",
        "body": "Body message"
    },
    "condition": "'match_1474' in topics"
}

The expected behaviour here is to receive the message in background executing immediately onMessage when it's not killed, but this happens only when app opens.

flutter doctor -v

[✓] Flutter (Channel stable, v1.17.4, on Mac OS X 10.15.3 19D76, locale pt-BR)
    • Flutter version 1.17.4 at /Users/fernando/Apps/flutter
    • Framework revision 1ad9baa8b9 (10 days ago), 2020-06-17 14:41:16 -0700
    • Engine revision ee76268252
    • Dart version 2.8.4
 
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
    • Android SDK at /Users/fernando/Library/Android/sdk
    • Platform android-29, build-tools 29.0.2
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 11.5)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 11.5, Build version 11E608c
    • CocoaPods version 1.8.4

[✓] Android Studio (version 4.0)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin version 46.0.2
    • Dart plugin version 193.7361
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)

[✓] VS Code (version 1.45.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.10.2

[✓] Connected device (1 available)
    • iPhone ... • ios • iOS 13.5.1

• No issues found!

pubspeck.yml dependencies

dependencies:
  flutter:
    sdk: flutter
  json_annotation: ^3.0.1
  jaguar_orm: ^2.2.7
  jaguar_query_sqflite: ^2.2.11
  device_info: ^0.4.2+4
  rxdart: ^0.22.2
  bloc_pattern: ^2.3.2
  dio: ^3.0.1
  intl: ^0.16.0
  sprintf: ^4.0.2
  firebase_messaging: ^6.0.16
  flutter_local_notifications: 1.4.3
  shared_preferences: ^0.5.6+1
  package_info: ^0.4.1
  mask_text_input_formatter: ^1.0.6
  admob_flutter: ^0.3.4
  archive: ^2.0.11
  appsflyer_sdk: ^5.2.0+1
  barcode_scan: ^1.0.0
  cached_network_image: ^2.0.0
  charts_flutter: ^0.8.1
  configurable_expansion_tile: ^1.0.0
  country_pickers: ^1.3.0
  cupertino_icons: ^0.1.3
  data_tables: ^1.0.3
  date_range_picker: ^1.0.5
  flare_flutter: ^1.0.2
  fl_chart: ^0.9.4
  flutter_cupertino_localizations: ^1.0.1
  flutter_slidable: ^0.5.3
  font_awesome_flutter: ^8.5.0
  image_picker: ^0.6.3+4
  path_provider: ^1.6.8
  provider: ^2.0.0
  pretty_qr_code: ^1.0.1
  share: ^0.6.3+6
  sqflite: ^1.2.0
  url_launcher: ^5.2.7
  webview_flutter: ^0.3.15+1
  google_sign_in: ^4.5.1
  flutter_svg: ^0.17.3+1
  flutter_localizations:
    sdk: flutter

[vuvantoan95]

same issues :(. Please help!

[whatamelon]

you can set content_available and priority option
In my case it solve the background and killed problem

[edjostenes]

I`m facing the same problem right now, I tried the same request and the problem persists.

[FernandoUFS]

you can set content_available and priority option
In my case it solve the background and killed problem

@whatamelon From apple, the content-available option is for:

content-available : The background notification flag. To perform a silent background update, specify the value 1 and don't include the alert, badge, or sound keys in your payload. See Pushing Background Updates to Your App.

I don't want a silent notification in background, I want a normal notification to show to the user. I need include "alert".
Anyway I tested content-available, it doesn't work :(

[robrichardson13]

I had the same issue. Pushes once worked but then randomly stopped working and I couldn't figure out why.

Here is a decent blog post on how to debug FCM for iOS: https://firebase.googleblog.com/2017/01/debugging-firebase-cloud-messaging-on.html

After following along I realized that my app was successfully getting the device token in didRegisterForRemoteNotificationsWithDeviceToken and was able to send pushes to my device via the NWPusher App which to me meant that FCM was simply failing to send to my APNS token.

I wish there was a way to be able to verify that your APNS token was in sync with your FCM token, but I assumed this could be the problem anyway.

I found at that at some point I disabled Swizzling by adding this to my plist:

<key>FirebaseAppDelegateProxyEnabled</key>
<false/>

*Some people mentioned changing this bool to a string NO would solve it, which simply just disables the flag re-enabling swizzling which turns back on the default APNS token set + analytics which could solve your issue too

I did this because I needed to grab the deviceToken for another purpose (use with Mixpanel). So in my AppDelegate.swift I override the didRegisterForRemoteNotificationsWithDeviceToken like so:

This is outlined in the references here:

  import FirebaseMessaging
  ...

  override func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
    Mixpanel.mainInstance().people.addPushDeviceToken(deviceToken) //For Mixpanel purposes, not needed if not using
    Messaging.messaging().apnsToken = deviceToken //*THIS WAS MISSING*
    super.application(application, didRegisterForRemoteNotificationsWithDeviceToken: deviceToken) //Not sure if calling super is required, but did anyway
  }

I realized that if you disable swizzling you must set the APNS token manually or FCM will never know the device token meaning remote or background notifications will never come to the app.

So simply adding this line into the didRegisterForRemoteNotificationsWithDeviceToken callback fixed my issue:

Messaging.messaging().apnsToken = deviceToken

Side note:

If you disable swizzling, the FCM analytics won't automatically work (for deliveries and opens) so you'll have to add this code in to ensure FCM knows about it.

This is outlined in the references here:

  override func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Swift.Void) {
    Messaging.messaging().appDidReceiveMessage(userInfo)
    ///Not sure if calling super is required here
    super.application(application, didReceiveRemoteNotification: userInfo, fetchCompletionHandler: completionHandler)
  }

[kmdinake]

@robrichardson13 Thanks for your solution, I did not realize that by disabling method swizzling I had to implement or call the functions that Firebase Message was handling in the background. In addition to the above, I would also emphasize that people call application.registerForRemoteNotifications() in the didFinishLaunchingWithOptions method as follows:

override func application(
    _ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
) -> Bool {
    if #available(iOS 10.0, *) {
      UNUserNotificationCenter.current().delegate = self as UNUserNotificationCenterDelegate
    }
    GeneratedPluginRegistrant.register(with: self)
    application.registerForRemoteNotifications()  //* I Forgot This Line *
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
}

[FernandoUFS]

Hi @robrichardson13 thank's for your reply.

First, I didn't have <key>FirebaseAppDelegateProxyEnabled</key> on my Info.plist.
Then I override the didRegisterForRemoteNotificationsWithDeviceToken on my AppDelegate.swift to get my device token and test at Pusher. Sending a push from Pusher worked. My app received and showed the notification in background.

So I added the <key>FirebaseAppDelegateProxyEnabled</key> to my Info.plist (tried the bool value false, and string value NO).
This is my didRegisterForRemoteNotificationsWithDeviceToken function

override func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        let deviceTokenString = deviceToken.reduce("", {$0 + String(format: "%02X", $1)})
        print("==== didRegisterForRemoteNotificationsWithDeviceToken ====")
        print(deviceTokenString)
        Messaging.messaging().apnsToken = deviceToken
}

But after that, it happened exactly like before. The FCM can't deliver the notifications when the app is in background, only when it is in foreground.

Also I tested sending from FCM directly to my device token (not using topics), I get the same result.

I conclude that if the firebase can deliver notifications when app is in foreground, then it has the apn token registered successfully on its backend. @robrichardson13 Am I right about this conclusion?

I didn't solve my problem yet. I know that APN is working because I tested on Pusher, but when it is sent from FCM it's not working. I am not sure if it's related to firebase_messaging plugin. It seems like a problem between FCM and APN.