iPhone 后台任务在某个时刻停止运行

Question

在我的 iPhone 应用程序中，我有一个后台任务，当应用程序进入后台状态时，该任务开始运行。该任务运行良好，并且结构如下所示:

运行。睡5分钟。运行。睡5分钟。

等等

由于某种原因，任务在一定时间后停止运行......比如半小时到一个小时。

谁能帮我理解为什么？这是后台任务代码:

- (void)applicationDidEnterBackground:(UIApplication *)application {    
NSLog(@"Application entered background state.");

if ([[NSUserDefaults standardUserDefaults] boolForKey:@"bgCheckSwitch"] == YES) {

    //UIApplication*    app = [UIApplication sharedApplication];



    // Request permission to run in the background. Provide an

    // expiration handler in case the task runs long.

    NSAssert(bgTask == UIBackgroundTaskInvalid, nil);



    bgTask = [application beginBackgroundTaskWithExpirationHandler:^{

        // Synchronize the cleanup call on the main thread in case

        // the task actually finishes at around the same time.

        dispatch_async(dispatch_get_main_queue(), ^{

            if (bgTask != UIBackgroundTaskInvalid)

            {

                [application endBackgroundTask:bgTask];

                bgTask = UIBackgroundTaskInvalid;

            }

        });

    }];



    // Start the long-running task and return immediately.

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{



        // Do the work associated with the task.

        [someClass doSomeThing]; //The actual method performed by the task. The looping is in the method.


        dispatch_async(dispatch_get_main_queue(), ^{

            if (bgTask != UIBackgroundTaskInvalid)

            {

                [application endBackgroundTask:bgTask];

                bgTask = UIBackgroundTaskInvalid;

            }

        });

    });


}

}

Answer 1

后台任务仅运行一段时间，然后操作系统将其终止。多任务 WWDC10 视频对此进行了讨论。