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]];
}