UIViewController可见回调 [英] UIViewController visible callback

问题描述

我正在开发一个iOS应用程序，当我有互联网连接时需要做一些事情，当我没有时。如果我还没有在某个时候，我会向用户显示一条消息，告诉我互联网并回来。问题是如何检测以下情况：

I am developing an iOS application where need to do some stuff when I have Internet connection and other, when I haven't. If I haven't at some point I will show a message to the user to give me internet and come back. The question it is how to detect the following situation:

• 用户按两次Home键，进入多任务，设置并将连接到互联网


• 用户通过多任务回到我的应用程序，但没有按任何东西

我知道我会收到AppDelegate的回调：

I know I will get callbacks to the AppDelegate:

- (void)applicationDidEnterBackground:(UIApplication *)application
- (void) applicationDidBecomeActive:(UIApplication *)application

但是代码（它不是由我启动的） ）它非常大，我不想在那里处理UIViewController需要，如果有任何替代方案。

but the code ( it is not started by me) it is very big, and I don't want to handle there the UIViewController needs, if there is any alternative.

我的UIViewController's - （void）viewDidAppear：（BOOL）动画当用户回来时不会调用它。

My UIViewController's - (void)viewDidAppear:(BOOL)animated it isn't called when the user came back.

断点不是肯定会被激活！

The breakpoint it is not hited for sure!

任何有用的想法，除了AppDelegate？

Any usable ideas, except in AppDelegate?

推荐答案

您可以使用通知中心在视图控制器中收听 applicationDidEnterBackground ：

You can use the notification center to listen to applicationDidEnterBackground within the view controller:

[[NSNotificationCenter defaultCenter] addObserver: self
                                      selector: @selector(handleEnteredBackground:) 
                                      name: UIApplicationDidEnterBackgroundNotification
                                      object: nil];

在 viewDidLoad 中执行此操作。类似于 applicationDidBecomeActive 。

Do this in viewDidLoad. Similarily for applicationDidBecomeActive.

不要忘记在 viewDidUnload中以观察者身份移除自己。

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