iPhone后台任务停止运行在某个点 [英] iPhone background task stops running at some point

问题描述

在我的iPhone应用程序我有当应用程序进入后台状态开始运行一个后台任务。
任务运行良好，并在一个循环的结构是这样的：

运行。
睡5分钟。
跑。
睡5分钟。

等。

由于某些原因，该任务将停止一定时间后运行......说一个半小时到一小时。

谁能帮我明白为什么？
这里是后台任务code：

   - （无效）applicationDidEnterBackground：（UIApplication的*）{应用
的NSLog（@应用程序进入背景状态。）;如果（[[NSUserDefaults的standardUserDefaults] boolForKey：@bgCheckSwitch] == YES）{    // *的UIApplication应用= [UIApplication的sharedApplication]    //请求允许在后台运行。提供    //如果到期处理任务运行长。    NSAssert（bgTask == UIBackgroundTaskInvalid，无）;    bgTask = [应用beginBackgroundTaskWithExpirationHandler：^ {        //同步的情况下，在主线程清理通话        //任务完成实际大约在同一时间。        dispatch_async（dispatch_get_main_queue（），^ {            如果（bgTask！= UIBackgroundTaskInvalid）            {                [应用endBackgroundTask：bgTask];                bgTask = UIBackgroundTaskInvalid;            }        }）;    }];    //开始长时间运行的任务，并立即返回。    dispatch_async（dispatch_get_global_queue（DISPATCH_QUEUE_PRIORITY_DEFAULT，0），^ {        //完成与任务相关的工作。        [SomeClass的DoSomething的]; //该任务执行的实际方法。该循环是在方法。
        dispatch_async（dispatch_get_main_queue（），^ {            如果（bgTask！= UIBackgroundTaskInvalid）            {                [应用endBackgroundTask：bgTask];                bgTask = UIBackgroundTaskInvalid;            }        }）;    }）;
}}
 

解决方案

一个后台任务只运行了一段时间，那么OS杀死它。这是在多任务WWDC10视频讨论

In my iPhone app I have a background task that starts running when the app enters the background state. The task runs fine and is structured in a loop like this:

run. sleep for 5 min. run. sleep for 5 min.

etc.

For some reason, the task stops running after a certain amount of time... say half an hour to an hour.

Can anyone help me understand why? Here is the background task code:

- (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;

            }

        });

    });


}

}

解决方案

A background task only runs for a period of time, then the OS kills it. This is discussed in the multitasking WWDC10 videos.

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