Handling Push Notifications when App is Terminated

问题:

When my App is not running and receives a Push Notification, if I click on that notification, the App is launched - but then it doesn't prompt the user with the Alert-View I set up, asking them whether they want to view the Notification's contents or not. It just launches, and sits there.

The Push Notifications do work perfectly when the App is running - either as the Active app or while in the background - but nothing works correctly when the app is not running.

I tried logging-out the launchOptions NSDictionary in application: didFinishLaunchingWithOptions: to see what load its bringing - but it comes up as "(null)". So It basically contains nothing - which doesn't make sense cause shouldn't it contain the Notification's load?

Anybody have any ideas how to make Push Notifications work when they arrive while the App was NOT running?

I mean how to handle the Push notifications when the App is in not running state. What if, if you receive many notifications & you did not open the app, neither did you tap the system's notification panel. How are you preserving those push for a later retrieval.

回答1:

As per your question, there is no way to hold all the notification when you open the app, better you call an api to get all notification as per time stamp from your back end/server that's how Facebook does.

回答2:

1) When application is running in background and When application is running in foreground application:didReceiveRemoteNotification: method will called as below.

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
{
    if (application.applicationState == UIApplicationStateInactive)
    {
        // opened from a push notification when the app was on background
        NSLog(@"userInfo->%@", [userInfo objectForKey:@"aps"]);
    }
    else if(application.applicationState == UIApplicationStateActive)
    {
        // a push notification when the app is running. So that you can display an alert and push in any view
        NSLog(@"userInfo->%@", [userInfo objectForKey:@"aps"]);
    }
}

2) When application is not launched (close) then application:didFinishedLaunchingWithOptions method will called.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    if (launchOptions != nil)
    {
        // opened from a push notification when the app is closed
        NSDictionary* userInfo = [launchOptions objectForKey:UIApplicationLaunchOptionsRemoteNotificationKey];
        if (userInfo != nil)
        {
             NSLog(@"userInfo->%@", [userInfo objectForKey:@"aps"]);
        }
    }
    else
    {
        // opened app without a push notification.
    }
}

3) There is no way to remove a specific notification as of. The way to remove all the notifications from your app so they don't show in the Notification Center when the user opens the app from one of them, is to set the app badge to 0.

回答3:

The app does not process push notification in the background, what it really does the OS is wake up the app once you press in the notification. You can catch this moment in the following way:

    - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
    { 

        if ([launchOptions objectForKey:UIApplicationLaunchOptionsRemoteNotificationKey]) {
      // Your app has been awoken by a notification...
        }
   }

回答4:

You can retrieve notifications delivered to your app by using the getDeliveredNotifications(completionHandler:) method. Note that this only returns notifications currently displayed in the Notification Center and not the ones that have been manually cleared by the user.

UNUserNotificationCenter.current().getDeliveredNotifications { notifications in

    // notifications: An array of UNNotification objects representing the local
    // and remote notifications of your app that have been delivered and are still
    // visible in Notification Center. If none of your app’s notifications are
    // visible in Notification Center, the array is empty.

    // As said in the documentation, this closure may be executed in a background
    // thread, so if you want to update your UI you'll need to do the following:
    DispatchQueue.main.sync { /* or .async {} */ 
        // update UI
    }
}

回答5:

There is no way of handling this on application end. You would need to maintain the unread badge count at the server. When the app is killed the badge value is updated from the server.

So when you open the application any time , you would need to call a web service to get the required notifications and update the badges of tabbar(if used).

回答6:

You can display the alert after launching a previously terminated app from a notification like this:

DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + 0.1) { // display the alert }