一旦iOS中的系统日期更改，如何更改带有日期的标签? [英] How can I change a label with a date once the system date changes in iOS?

问题描述

我有一个简单的查询，但不知道该怎么做.

I have a simple query but don't know how to do it.

这就是我想要实现的目标:1)我有一个带有今天日期的 UILabel，即29/04/12"2) 在午夜，我希望该标签自动更新为30/04/12"，而无需更改视图或按下任何按钮.

This is what I am trying to achieve: 1) I have a UILabel with todays date i.e. "29/04/12" 2) At midnight I want that label to update by itself to "30/04/12" without needing to change view or press anything.

这是我不知道该怎么做的第 2 步.我知道如何完成它，例如可能会收到日期更改的系统通知(如果可能的话)或使用某种计时器作为触发器.

It's step 2 that I don't know how to do. I have idea's of how it would be done such as potentially getting a system notification of the date change (if this is even possible) or using some sort of timer as a trigger.

任何帮助将不胜感激，提前致谢.

Any help would be greatly appreciated, thanks in advance.

推荐答案

如果您只想在午夜到来时收到通知(或其他几种情况)，那么您可以覆盖 UIApplicationDelegate 的 - (void)applicationSignificantTimeChange:(UIApplication *)application 方法，以便它导致您的标签更新.当然，您还需要在应用程序重新进入前台时更新标签，因为如果日期更改时您的应用程序在后台，则不会调用此方法.

If you are only interested in being notified when midnight arrives (or a couple other cases), then you can override UIApplicationDelegate's - (void)applicationSignificantTimeChange:(UIApplication *)application method so that it causes your labels to update. Of course, you'll also want to update the labels whenever the application re-enters the foreground, since this method won't be called if your app is in the background when the date changes.

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