设备时间变化（分钟）时的 NSNotification？
有没有办法可以在 iOS 设备的系统时间分钟发生变化时轻松设置通知？
我需要针对时间变化进行一些 UI 更新。我希望 UI 能够准确地更新每分钟的更改，而不是通过 NSTimer 触发器每 60 秒更新一次。
Is there a way I can easily set up a notification when the minutes change on the system time for iOS devices?
I need to do some UI updates for time changes. I'd like the UI to update exactly on minute changes, not just every 60 seconds through an NSTimer trigger.
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API 不提供任何通知，但您可以通过让后台线程轮询系统时间，然后向主线程上的 UI 发送自定义通知来推出自己的通知。
不过，我不会打扰。您无法在任何具有软件 UI 的设备上“精确”管理时间。您能做的最好的事情就是让 UI 更新发生在用户感知的阈值以下。人类无法真正感知小于 100-200 毫秒（1/10 秒）的时间间隔。任何更精确的 UI 都是浪费。只要应用程序的其他部分没有挂起或陷入困境，NSTimer 就可以非常可靠地达到 100 毫秒的窗口。
除非您使用 NSTimer 测试了接口并发现它不合要求，否则我不会去寻找增加复杂性的方法。
There are no notifications provided by the API but you could roll your own by having a background thread polling the system time and then sending a custom notification to the UI on the main thread.
However, I wouldn't bother. You can't manage time "exactly" on any device with a software UI. The best you can do is get the UI updates to occur below the threshold of user perceptions. Humans can't really perceive time intervals of less than 100-200 milliseconds (1/10th second). Any UI more precise is wasted. A NSTimer can very reliably hit a 100 millisecond window as long as some other part of the app doesn't hang or bog.
Unless you've tested the interface using a NSTimer and found it wanting, I wouldn't go looking for adding complexity.