我可以调用ViewController类中的哪个方法来检查它何时被带到前台？

Question

我可以调用ViewController类中的哪个方法来检查它何时被带到前台？

例如,我在我的应用程序上查看一个页面,然后我决定关闭该应用程序并稍后再回到它.当我回到它时,屏幕上显示的是我所看到的相同视图.但是......一旦我打开应用程序,我想转到另一个视图.

我怎样才能做到这一点？

目前尝试这个:

 - (void) applicationDidBecomeActive:(NSNotification*) notification
{
    [self checkActivity];
    // Do your stuff here
}


- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(applicationWillEnterForeground:)
                                                     name:UIApplicationWillEnterForegroundNotification
                                                   object:nil];
        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(applicationDidBecomeActive:)
                                                     name:UIApplicationDidBecomeActiveNotification
                                                   object:nil];
    }
    return self;
}

- (void)checkActivity{
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    NSLog(@"Checking if re-authentication required...");
    if([[defaults objectForKey:@"shouldgotologin"] isEqualToString:@"yes"]){
        NSLog(@"View Should go to login...performing segue");
        [defaults setObject:@"no" forKey:@"shouldgotologin"];
        [defaults synchronize];
        [self performSegueWithIdentifier:@"backtologin" sender:self];
    } else {
        NSLog(@"Should go to login is not true.");
    }
}

Answer 1

注册您的视图控制器以观察UIApplicationWillEnterForegroundNotification:

1)内部视图控制器的init方法:

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(applicationWillEnterForeground:)
                                             name:UIApplicationWillEnterForegroundNotification
                                           object:nil];

2)内部视图控制器的dealloc方法:

[[NSNotificationCenter defaultCenter] removeObserver:self];

3)此外,让您的视图控制器实现此方法:

- (void) applicationWillEnterForeground:(NSNotification*) notification
{
    // This method will be called just before entering the foreground;
    // Do your stuff here
}

如果时间UIApplicationWillEnterForegroundNotification不适合您,请查看UIApplication此处的所有可用通知:http: //developer.apple.com/library/ios/#DOCUMENTATION/UIKit/Reference/UIApplication_Class/Reference/Reference.html