UIApplicationMain(argc, argv,nil,NSStringFromClass([StartingPointAppDelegateclass]));

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {}

- (void)applicationWillEnterForeground:(UIApplication *)application {}
程序将置于前台，程序启动的时候不会相应此方法，而是按下home以后再次回复程序的时候响应。- (void)applicationDidBecomeActive:(UIApplication *)application {}
程序已经置于前台，程序刚启动也会响应此方法。按下home以后再次回来也会响应。- (void)applicationWillResignActive:(UIApplication *)application {}
程序将要退出后台，按下home以后，程序不会立即消失，系统会先调用此方法。- (void)applicationDidEnterBackground:(UIApplication *)application {}
程序已经置于后台了，按home以后，程序完全消失会调用。

// AppDelegate.h@property (assign, nonatomic) UIBackgroundTaskIdentifier* backgroundTaskIdentifier;// AppDelegate.m- (void)applicationDidEnterBackground:(UIApplication *)application {[self beingBackgroundUpdateTask];NSLog(@"加上你需要多久运行的代码"); NSLog(@"剩余执行时间: %f", [[UIApplication sharedApplication] backgroundTimeRemaining]);[self endBackgroundUpdateTask];
}-(void) beingBackgroundUpdateTask {self.backgroundTaskIdentifier = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{[self endBackgroundUpdateTask];}];
}-(void) endBackgroundUpdateTask {[[UIApplication sharedApplication] endBackgroundTask: self.backgroundTaskIdentifier];self.backgroundTaskIdentifier = UIBackgroundTaskInvalid;}

[[UIApplication sharedApplication] setKeepAliveTimeout:600 handler:^{//执行你想要执行的任务，同时可以配合第一种任务，以增加某些同步方法的执行时间，比如说下载数据等}];