iOS应用在后台长久运行

// AppDelegate.h
@property (nonatomic, strong)UIBackgroundTaskIdentifier backgroundUpdateTask;

// AppDelegate.m文件
- (void)applicationDidEnterBackground:(UIApplication *)application{
typeof(self) weakSelf =self;
self.backgroundUpdateTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
[weakSelf endBackgroundUpdateTask];
}];
}

- (void)endBackgroundUpdateTask{
[[UIApplication sharedApplication] endBackgroundTask:self.backgroundUpdateTask];
self.backgroundUpdateTask = UIBackgroundTaskInvalid;
}