在后台重新加载推送通知徽章

Question

I am creating a notification service using swift3 in xcode 10. The problem now is that when a push notification comes in the background (even when the app is closed), the badge does not increase at first, but increases by 1 from the second push notification. Furthermore, when I enter the app and come back in the background, the number of badges will be normal, but the above problem will happen again.

I tried to check the problem through delay or local notifications, but I have not been able to figure out what the problem is.

Below are the notifications related to the notifications within the AppDelegate. Push Notification Click event also works normally.

class AppDelegate: UIResponder, UIApplicationDelegate, GIDSignInDelegate, NaverThirdPartyLoginConnectionDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions:[UIApplicationLaunchOptionsKey: Any]?) -> Bool {
        UNUserNotificationCenter.current().delegate = self
        UNUserNotificationCenter.current().requestAuthorization(options: [.badge, .sound, .alert,], completionHandler: {(granted, error) in
            if (granted)
            {
                application.registerForRemoteNotifications()
            }
            else{
            }
        })
        return true
}

...
... 
extension AppDelegate: UNUserNotificationCenterDelegate {
    func userNotificationCenter(_ center: UNUserNotificationCenter, willPresent notification: UNNotification, withCompletionHandler completionHandler: @escaping (UNNotificationPresentationOptions) -> Void) {
        completionHandler([.badge, .alert, .sound])
        UIApplication.shared.applicationIconBadgeNumber = UIApplication.shared.applicationIconBadgeNumber + 1
        }

    func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {
        print("userInfo: \(response.notification.request.content.userInfo)")
        var userInfo:[AnyHashable: Any]?
        let pushId:Int32 = userInfo?["uid"] as! Int32
        self.moveView(pushId)// My app load method
    }
}

Answer 1

Running app in the background state is just a brief stop on the way to the app being suspended. While suspended, an app remains in memory but does not execute any code. For this reason your code is not executing and thus badge value does not update. See these below link to about application state and background execution.

• Application State
• Background Execution

So better approach to solve this problem is to send send badge value inside of push notification payload. eg

{
    "aps" : {
        "alert" : {
            "title" : "Game Request",
            "body" : "Bob wants to play poker",
            "action-loc-key" : "PLAY"
        },
        "badge" : 5
    },
    "acme1" : "bar",
    "acme2" : [ "bang",  "whiz" ]
}

See this link to create remote notification payload

• Creating the Notification Payload

Don't increase badge value programmatically unless you need to show badge for local notification. If you want to execute code on background while push notification receive, use VoIP push notification which has few restriction eg app must be related VoIP services.

I recommend to change the push notification payload.

Thanks.