Will iOS launch my app into the background if it was force-quit by the user?

ghz 1years ago ⋅ 557 views

Question

I am triggering a background fetch by using the content-available flag on a push notification. I have the fetch and remote-notification UIBackgroundModes enabled.

Here is the implementation I am using in my AppDelegate.m:

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler
{
    NSLog(@"Remote Notification Recieved");
    UILocalNotification *notification = [[UILocalNotification alloc] init];
    notification.alertBody =  @"Looks like i got a notification - fetch thingy";
    [application presentLocalNotificationNow:notification];
    completionHandler(UIBackgroundFetchResultNewData);

}

When the app is running in the background, it works fine. (The notification is received and the app triggered the "looks like i got a notification" local notification, as the code above should do).

However, when the app is not running and a push notification is received with the content-available flag, the app is not launched and the didRecieveRemoteNotification delegate method is never called.

The WWDC Video Whats New With Multitasking (#204 from WWDC 2013) shows this: enter image description here

It says that the application is "launched into background" when a push notification is received with the content-available flag.

Why is my app not launching into the background?

So the real question is:

Will iOS perform background tasks after the user has force-quit the app?

Answer

UPDATE2:

You can achieve this using the new PushKit framework, introduced in iOS 8. Though PushKit is used for VoIP. So your usage should be for VoIP related otherwise there is risk of app rejection. (See this answer).

UDPDATE1:

The documentation has been clarified for iOS8. The documentation can be read here. Here is a relevant excerpt:

Use this method to process incoming remote notifications for your app. Unlike the application:didReceiveRemoteNotification: method, which is called only when your app is running in the foreground, the system calls this method when your app is running in the foreground or background. In addition, if you enabled the remote notifications background mode, the system launches your app (or wakes it from the suspended state) and puts it in the background state when a push notification arrives. However, the system does not automatically launch your app if the user has force-quit it. In that situation, the user must relaunch your app or restart the device before the system attempts to launch your app automatically again.

Although this was not made clear by the WWDC video, a quick search on the developer forums turned this up:

https://devforums.apple.com/message/873265#873265 (login required)

Also keep in mind that if you kill your app from the app switcher (i.e. swiping up to kill the app) then the OS will never relaunch the app regardless of push notification or background fetch. In this case the user has to manually relaunch the app once and then from that point forward the background activities will be invoked. -pmarcos

That post was by an Apple employee so I think i can trust that this information is correct.

So it looks like when the app is killed from the app switcher (by swiping up), the app will never be launched, even for scheduled background fetches.

#ios