如何在应用程序处于后台时通过iCloud检查我的UIDocument是否已更新？

Question

I noticed that UIDocument's methods to let the app know of a change, such as presentedItemDidChange , only get called if the app is running in the foreground.

What I'm wondering is, if the user was to switch apps or send my app to the background, how can I know if the UIDocument has changed since the user last saw it when they bring the app to the foreground again?

Or, should I be updating everything every time the app returns to the foreground just in case the UIDocument has been updated?

Answer 1

uidocument自己处理所有更改通知，因此如果文档在其他设备中更改，将自动调用loadFromContents：ofType：error：以反映这些更改，因此您唯一需要做的就是实现此方法。