应用程序进入后台之后的延时操作

@interface AppDelegate ()
@property (assign,nonatomic) UIBackgroundTaskIdentifier backgroundUpdateTask;
@end

@implementation AppDelegate

- (void)applicationDidEnterBackground:(UIApplication *)application {
[self beingBackgroundUpdateTask];

// 做一些长久运行的代码

[self endBackgroundUpdateTask];

}

- (void)beingBackgroundUpdateTask
{
self.backgroundUpdateTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
[self endBackgroundUpdateTask];
}];
}

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