AppDelegate 中背景/前景方法的使用

问题描述

我计划在我的应用中实现多任务.我可以在这里看到许多方法在 AppDelegate 中做到这一点，例如 applicationWillResignActive、applicationDidEnterBackground、applicationWillEnterForeground，...

I'm planning to implement multi-task in my app.I can see many methods here to do that in the AppDelegate like applicationWillResignActive, applicationDidEnterBackground, applicationWillEnterForeground, ...

但是......我不明白它们应该被使用的方式，也不明白为什么它们不在 ViewControllers 中......也不明白它们在这里的用途.

But.... I don't see the way they should be used, nor why they are not in the ViewControllers... Nor what they are here for.

我的意思是:当应用程序进入后台时，我不知道我的用户在哪个视图上.然后，当应用程序进入前台时，我如何知道要做什么以及我可以调用什么，例如更新视图?

I mean : when the app enter in background, i don't know on which view my user is.And back, when the app comes into foreground, how would I know what to do and what I may call, to update the view for example ?

我会理解这些方法是否在每个视图控制器中，但在这里，我没有看到它们可以具体用于什么......

I would have understood if those methods where in each view controller, but here, I don't see what they can be used for in a concrete way...

你能帮我理解在这些方法中实现事物的方式吗?

Can you help me to understand the way to implement things into those methods ?

推荐答案

当应用程序进入后台时，每个对象都会收到一个 UIApplicationDidEnterBackgroundNotification 通知.因此，要在应用程序进入后台时运行一些代码，您只需在需要的地方收听该通知:

Each object receive a UIApplicationDidEnterBackgroundNotification notification when the app goes in background. So to run some code when the app goes in background, you just have to listen to that notification where you want :

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

当您不再需要收听时，不要忘记释放收听者:

Don't forget to release the listener when you don't need to listen to it anymore :

[[NSNotificationCenter defaultCenter] removeObserver:self];

最好的，您可以通过以下通知以相同的方式进行游戏:

And best of the best, you can play the same way with the following notifications :

• UIApplicationDidEnterBackgroundNotification
• UIApplicationWillEnterForegroundNotification
• UIApplicationWillResignActiveNotification
• UIApplicationDidBecomeActiveNotification

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