Push notification is not working when app is in background (minimized) - iOS

Question

I'm newbie to Swift, I am creating chat application, I need to send notification when app is in foreground or minimized.

But I am not getting the notification when app is minimized (it works when USB is connected.

1. Enabled Remote notification

2. Background Fetches in Xcode setup

3. Enabled Push Notification

4. Production APns certificate

Notification code:

class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?
    let gcmMessageIDKey = "gcm.message_id"

    func application(_ application: UIApplication,
                     didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

        FirebaseApp.configure()

        Messaging.messaging().delegate = self
        Messaging.messaging().shouldEstablishDirectChannel = true

        if #available(iOS 10.0, *) {

            UNUserNotificationCenter.current().delegate = self

            let authOptions: UNAuthorizationOptions = [.alert, .sound, .badge]
            UNUserNotificationCenter.current().requestAuthorization(
                options: authOptions,
                completionHandler: {_, _ in })
        } else {
            let settings: UIUserNotificationSettings =
                UIUserNotificationSettings(types: [.alert, .sound, .badge], categories: nil)
            application.registerUserNotificationSettings(settings)
        }

        application.registerForRemoteNotifications()

        NotificationCenter.default.addObserver(self, selector: #selector(tokenRefreshNotification(_:)), name: NSNotification.Name.InstanceIDTokenRefresh, object: nil)

        return true
    }

    func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable: Any]) {

        Messaging.messaging().appDidReceiveMessage(userInfo)         
    }

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

        Messaging.messaging().appDidReceiveMessage(userInfo)

        let action = userInfo["action"] as! String
        let notification = UILocalNotification()
        notification.fireDate = NSDate() as Date
        notification.alertTitle = "test"
        notification.alertBody = "test"
        notification.alertAction = "Ok"
        UIApplication.shared.applicationIconBadgeNumber =  1
        UIApplication.shared.scheduleLocalNotification(notification)

        completionHandler(UIBackgroundFetchResult.newData)
    }

    func application(_ application: UIApplication, didFailToRegisterForRemoteNotificationsWithError error: Error) {
        print("Unable to register for remote notifications: \(error.localizedDescription)")
    }

    func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
        print("APNs token retrieved: \(deviceToken)")

        // With swizzling disabled you must set the APNs token here.
        Messaging.messaging().apnsToken = deviceToken
    }       
}

@available(iOS 10, *)
extension AppDelegate : UNUserNotificationCenterDelegate {

    func userNotificationCenter(_ center: UNUserNotificationCenter,
                                willPresent notification: UNNotification,
                                withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
        let userInfo = notification.request.content.userInfo

        if let messageID = userInfo[gcmMessageIDKey] {
            print("Message ID: \(messageID)")
        }

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

    func userNotificationCenter(_ center: UNUserNotificationCenter,
                                didReceive response: UNNotificationResponse,
                                withCompletionHandler completionHandler: @escaping () -> Void) {
        let userInfo = response.notification.request.content.userInfo

        if let messageID = userInfo[gcmMessageIDKey] {
            print("Message ID: \(messageID)")
        }

        print(userInfo)

        completionHandler()
    }
    @objc func tokenRefreshNotification(_ notification: Notification) {
            guard let token = InstanceID.instanceID().token() else {
            print("No firebase token, aborting registering device")
            return
        }
        print("No firebase token, aborting registering device")           
    }
}   

extension AppDelegate : MessagingDelegate {
    // [START refresh_token]
    func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String) {
        print("Firebase registration token: \(fcmToken)")
        Messaging.messaging().subscribe(toTopic: "/topics/channel_18")           
    }

    func messaging(_ messaging: Messaging, didReceive remoteMessage: MessagingRemoteMessage) {
        print("Received data message: \(remoteMessage.appData)")
    }        
}

FCM Payload:

 {
     "to" : "/topics/channel_18",
     "data" : {
      "action" : "NOTIFY",
      "message" : "{"text":"test" }"
     },
     "content_available" : true
    }

I have tried with Priority high and with Sound option but none works.

Please note that I am not using "notification" key as per client request. i am using only data-message in FCM payload

Please anyone help me to work notification when app is in background without USB connection.

Answer 1

If it works with non-Silent notification then all it means is:

• Then payload is not correctly setup. Based on the answers provided to this question I'd just alter the placement of the content_available field into notification(and since you don't want a title body then just don't add title/body) or just into the payload itself until see it working.
• I'd also make sure all the correct capabilities in Xcode are set (Enabled Remote notification, Background Fetches in Xcode setup, Enabled Push Notification). As mentioned previously uncheck and recheck all of them again.
• And make sure Background App refresh is enabled for your app. This is NOT the same with your notifications. Obviously make sure your notifications are also enabled.:

• But if you tried everything and it just doesn't work for 11.3 then it might be a bug. There is this other open question mentioned the same issue of yours. Run the app directly from tapping the app, ie not launching from Xcode and then use the console to see what it's logging related to the silent notification. If you're getting something like this:

default 13:11:47.178186 +0200   dasd    DuetActivitySchedulerDaemon Removing a launch request for application <private> by activity <private>   default com.apple.duetactivityscheduler

Then likely it's a bug similar to this iOS11 question. But you must open a new radar, because that radar was closed I believe because it was fixed!