IOS 前后台切换

- (void)applicationDidEnterBackground {
	NSLog(@"=======applicationDidEnterBackground========");
}

- (void)applicationWillEnterForeground {
	[CheckNetwork isExistenceNetwork];
	NSLog(@"=======applicationWillEnterForeground========");
}

- (void)viewDidLoad {
    [super viewDidLoad];
	[UIApplication sharedApplication].statusBarHidden = NO;
	
	[[NSNotificationCenter defaultCenter] addObserver:self 
											 selector:@selector(applicationDidEnterBackground)
												 name:UIApplicationDidEnterBackgroundNotification
													object:[UIApplication sharedApplication]];
	[[NSNotificationCenter defaultCenter] addObserver:self 
											 selector:@selector(applicationWillEnterForeground)
												 name:UIApplicationWillEnterForegroundNotification
											   object:[UIApplication sharedApplication]];
}

转载：http://blog.youkuaiyun.com/xiaojunhu/article/details/7068583