didReceiveRemoteNotification not working in the background

Question

I'm working on a big app with a huge chunk of legacy code. Currently - there's an implementation for:

- (void) application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo

The problem is that it is only called when the app is in the foreground OR when the user taps the the notification while the app is in the background. I tried to implement:

- (void) application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler

But the app behaves the same. In any case - this method is not called when the app is in the background. What could be the problem?

Answer 1

Implementing didReceiveRemoteNotification and didReceiveRemoteNotification:fetchCompletionHandler is the correct way, but you also need to do the following:

Make sure to register for remote notifications, see documentation here:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{    
    [[UIApplication sharedApplication] registerForRemoteNotificationTypes:(UIRemoteNotificationTypeAlert | UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeSound)];

    return YES;
}

Also make sure to edit Info.plist and check the "Enable Background Modes" and "Remote notifications" check boxes:

Additionally, you need to add "content-available":1 to your push notification payload, otherwise the app won't be woken if it's in the background (see documentation here updated):

For a push notification to trigger a download operation, the notification’s payload must include the content-available key with its value set to 1. When that key is present, the system wakes the app in the background (or launches it into the background) and calls the app delegate’s application:didReceiveRemoteNotification:fetchCompletionHandler: method. Your implementation of that method should download the relevant content and integrate it into your app

So payload should at least look like this:

{
    aps = {
        "content-available" : 1,
        sound : ""
    };
}

Answer 2

1. Register for push notification in app delegate.
2. Add background mode in app capabilities.
3. Add "content-available"="1" while sending the push notification(if you are using firebase replace "content-available"="1" by "content_available"="true" while sending the push notification from server side).

Answer 3

I had the same problem. Notification banner appeared, but -application:didReceiveRemoteNotification:fetchCompletionHandler: method was not called. The solution for me that worked was to add implementation of - application:didReceiveRemoteNotification: method and forward call to -application:didReceiveRemoteNotification:fetchCompletionHandler::

func application(application: UIApplication, didReceiveRemoteNotification userInfo: [NSObject : AnyObject]) {

    self.application(application, didReceiveRemoteNotification: userInfo) { (UIBackgroundFetchResult) in

    }
}

Answer 4

I am creating an iOS project that will use Firebase Cloud Messaging (FCM) to deliver custom data elements, sent via Firebase/APNS notifications, from a company server to the iOS device.

The first thing I had to understand is that unlike Android, there is no similar type of 'Service' that will be able to capture and save information I'm sending, regardless if the app is in the foreground (active), background (still in memory) or not active (not in memory). Therefore, I have to use Notification messages NOT Data messages like I had designed for Android.

After much reading to understand both Apple APNS and the Firebase interface between the iOS app and APNS server, looking at countless posts on stackoverflow and other web resources, I finally figured out how to get this to work for my requirements.

When a Firebase Cloud Messaging (FCM) Notification message is sent from the server (or Firebase Console as the FCM defaults to Notification NOT Data messages), it is delivered via APNS and presented as a notification on the iOS device. When the user taps on the notification banner, iOS does the following: if the app is not running/loaded iOS launches the app, if the app is loaded/running but in the background iOS brings the app to the foreground OR if the app is in the foreground (all three cases), the message content is then delivered via func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: (UIBackgroundFetchResult) -> Void) {}.

One thing for sure, you Must Enable Background Modes and check Remote Notification, you DO NOT have to include {"content-available" : 1} in the payload.

1) Go through the APNS and Firebase setup, pretty straight forward, generate and register certificates and such.

2) In appDelegate, didFinishLaunchingWithOptions, add:

        Messaging.messaging().delegate = self as? MessagingDelegate

        if #available(iOS 10.0, *) {

            UNUserNotificationCenter.current().delegate = self

            let authOptions: UNAuthorizationOptions = [.alert, .badge, .sound]

            UNUserNotificationCenter.current().requestAuthorization(
                options: authOptions,
                completionHandler: {_, _ in })
        }
        else {

            let settings: UIUserNotificationSettings =
                UIUserNotificationSettings(types: [.alert, .badge, .sound], categories: nil)

            application.registerUserNotificationSettings(settings)
        }

        application.registerForRemoteNotifications()

3) Then add these call back functions to appDelegate:

    func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: (UIBackgroundFetchResult) -> Void) {

        // Print message ID.
        if let messageID = userInfo["gcm.message_id"] {

            print("\n*** application - didReceiveRemoteNotification - fetchCompletionHandler - Message ID: \(messageID)")
        }

        // Print full message.
        print("\n*** application - didReceiveRemoteNotification - full message - fetchCompletionHandler, userInfo: \(userInfo)")

        myNotificationService?.processMessage(title: userInfo["Title"] as! String
            , text: userInfo["Text"] as! String, completion: { (success) in

                if success {
                    completionHandler(.newData)
                }
                else {
                    completionHandler(.noData)
                }
        })
    }

    func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {

        completionHandler([.alert, .badge, .sound])
    }

Very Helpful:

https://developer.apple.com/library/archive/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/CreatingtheNotificationPayload.html

https://firebase.googleblog.com/2017/01/debugging-firebase-cloud-messaging-on.html

Answer 5

My device was in a bad state. I had to restart the device to get it working although I had done all the pre-requisites mentioned here.