blocks|key|2923851|text|UIWindow可以浮动在其他UI元素之上，如系统键盘。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2923852|最后一段:创建一个与主窗口具有相同框架的UIWindow。将其windowLevel属性设置为UIWindowLevelStatusBar。将其hidden属性设置为NO。|2923853|entityMap^0|0|8|0|K|8|V|B|1B|M|20|6|2B|2|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|H|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|I|$]]

A <code>UIWindow</code> can float above other UI elements like the system keyboard.

To address your last paragraph: Make a <code>UIWindow</code> with the same frame as your main window. Set its <code>windowLevel</code> property to <code>UIWindowLevelStatusBar</code>. Set its <code>hidden</code> property to <code>NO</code>.

blocks|key|250144|text|从Rob的回答开始，我稍微玩玩了一下，并想写下一些笔记，以供其他试图获取此主题信息的人参考：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|250145|250146|添加另一个UIWindow根本不是问题。只需创建一个和makeKeyAndVisible即可。完成。|unordered-list-item|offset|length|style|CODE|250147|通过使另一个窗口可见来移除它，然后释放你不再需要的窗口。|250148|是“键”的窗口接收所有键盘input.|250149|UIWindow覆盖一切，甚至模态，弹出，等等。Brilliant!|250150|UIWindow总是隐式的肖像。它不会旋转。您必须添加一个控制器作为新窗口的根控制器，并让它处理旋转。(就像主窗口一样)|250151|窗口的级别决定了它的显示高度。将其设置为UIWindowLevelStatusBar，以使其覆盖所有内容。将其hidden属性设置为NO。|250152|第二个UIWindow可用于在屏幕上显示浮动在所有内容之上的视图。无需创建一个虚拟控制器就可以将其嵌入到UIPopoverController.|250153|It中，这在iPhone上特别有用，因为它没有弹出式控制器，但你可能想要模仿一些类似的东西。|250154|当然，它解决了我的问题:如果应用程序放弃激活，在当前显示的内容上添加一个覆盖窗口，以防止iOS截取应用程序当前内容的屏幕截图。|250155|250156|entityMap^0|0|0|5|8|R|H|0|0|0|0|8|0|0|8|0|K|M|1J|6|0|3|8|1G|J|0|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|13|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|14|8|@$F|15|G|16|H|I]|$F|17|G|18|H|I]]|9|@]|A|$]]|$1|J|3|K|5|E|7|19|8|@]|9|@]|A|$]]|$1|L|3|M|5|E|7|1A|8|@]|9|@]|A|$]]|$1|N|3|O|5|E|7|1B|8|@$F|1C|G|1D|H|I]]|9|@]|A|$]]|$1|P|3|Q|5|E|7|1E|8|@$F|1F|G|1G|H|I]]|9|@]|A|$]]|$1|R|3|S|5|E|7|1H|8|@$F|1I|G|1J|H|I]|$F|1K|G|1L|H|I]]|9|@]|A|$]]|$1|T|3|U|5|E|7|1M|8|@$F|1N|G|1O|H|I]|$F|1P|G|1Q|H|I]]|9|@]|A|$]]|$1|V|3|W|5|E|7|1R|8|@]|9|@]|A|$]]|$1|X|3|Y|5|E|7|1S|8|@]|9|@]|A|$]]|$1|Z|3|-4|5|6|7|1T|8|@]|9|@]|A|$]]|$1|10|3|-4|5|6|7|1U|8|@]|9|@]|A|$]]]|11|$]]

Starting with Rob's answer I played around a bit and would like to write down some notes for others trying to get information on this topic:

<ul>
<li>It is not a problem at all to add another <code>UIWindow</code>. Just create one and <code>makeKeyAndVisible</code>. Done.</li>
<li>Remove it by making another window visible, then release the one you don't need anymore.</li>
<li>The window that is "key" receives all the keyboard input.</li>
<li><code>UIWindow</code> covers everything, even modals, popovers, etc. Brilliant!</li>
<li><code>UIWindow</code> is always portrait implicitly. It does no rotate. You'll have to add a controller as the new window's root controller and let that handle rotation. (Just like the main window)</li>
<li>The window's level determines how "high" it gets displayed. Set it to <code>UIWindowLevelStatusBar</code> to have it cover everything. Set its <code>hidden</code> property to NO.</li>
<li>A 2nd <code>UIWindow</code> can be used to bring views on the screen that float on top of everything. Without creating a dummy controller just to embed that in a <code>UIPopoverController</code>.</li>
<li>It can be especially useful on iPhone where there is no popover controller but where you might want to mimic something like it.</li>
<li>And yes, it solved of course my problem: if the app resigns activation, add a cover window over whatever is currently shown to prevent iOS from taking a screenshot of your app's current content.</li>
</ul>

blocks|key|2923988|text|这里是苹果的文档，以更好地理解UIWindow：https://developer.apple.com/library/archive/documentation/WindowsViews/Conceptual/WindowAndScreenGuide/WindowScreenRolesinApp/WindowScreenRolesinApp.html|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|2923989|使用多个UIWindow实例的一个很好的具体原因是当您需要对应用程序屏幕进行视频录制时。您可能不想包含某些元素(录制按钮、录制状态等)在最终录制的视频中，所以您可以将这些元素放在顶部的单独UIWindow中。|2923990|实际上，如果您使用的是ReplayKit，则必须为这些排除的UI元素使用单独的UIWindow。更多信息请点击此处：https://medium.com/ar-tips-and-tricks/how-to-record-a-screen-capture-with-replaykit-whilst-hiding-the-hud-element-bedcca8e31e|2923991|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.apple.com/library/archive/documentation/WindowsViews/Conceptual/WindowAndScreenGuide/WindowScreenRolesinApp/WindowScreenRolesinApp.html|1|https://medium.com/ar-tips-and-tricks/how-to-record-a-screen-capture-with-replaykit-whilst-hiding-the-hud-element-bedcca8e31e^0|3|5|O|49|0|0|0|1M|3H|1|0^^$0|@$1|2|3|4|5|6|7|T|8|@$9|U|A|V|B|C]]|D|@$9|W|A|X|1|Y]]|E|$]]|$1|F|3|G|5|6|7|Z|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|10|8|@]|D|@$9|11|A|12|1|13]]|E|$]]|$1|J|3|-4|5|6|7|14|8|@]|D|@]|E|$]]]|K|$L|$5|M|N|O|E|$P|Q]]|R|$5|M|N|O|E|$P|S]]]]

Here is Apple's Documentation for better understanding UIWindow:
<a href="https://developer.apple.com/library/archive/documentation/WindowsViews/Conceptual/WindowAndScreenGuide/WindowScreenRolesinApp/WindowScreenRolesinApp.html" rel="nofollow noreferrer">https://developer.apple.com/library/archive/documentation/WindowsViews/Conceptual/WindowAndScreenGuide/WindowScreenRolesinApp/WindowScreenRolesinApp.html</a>

One good though specific reason to use multiple instances of UIWindow is when you need to video record the app screen. You may not want to include certain elements (recording button, recording status, etc.) in the final recorded video, so you can put those elements in a separate UIWindow on top. 

In fact, if you are using ReplayKit, you will have to use a separate UIWindow for these excluded UI elements. More info here: <a href="https://medium.com/ar-tips-and-tricks/how-to-record-a-screen-capture-with-replaykit-whilst-hiding-the-hud-element-bedcca8e31e" rel="nofollow noreferrer">https://medium.com/ar-tips-and-tricks/how-to-record-a-screen-capture-with-replaykit-whilst-hiding-the-hud-element-bedcca8e31e</a>

Recently I've been wondering about the fact that that an iOS app only has one <code>UIWindow</code>.
It does not seem to be an issue to create another <code>UIWindow</code> and place it on screen.

My question is kind of vague, but I'm interested in:

<ul>
<li>What could I potentially achieve with a second <code>UIWindow</code> that cannot be done in other ways?</li>
<li>What can go wrong when using multiple <code>UIWindow</code> instances?</li>
<li>I have seen that people use a 2nd <code>UIWindow</code> to display popover like views on iPhone. Is this a good way of doing it? Why? Why not?</li>
<li>Are there other examples where it is making perfectly sense to have another <code>UIWindow</code>?</li>
</ul>

It's not that I'm missing something. I have never felt the need to create another <code>UIWindow</code> instance but maybe it would allow doing amazing things I'm not aware of! :-)

I'm hoping that it might help me solve this problem:
I need to add a "cover view" over whatever is currently displayed. It should also work if there are already one or more modal controllers presented. If I add a <code>UIView</code> to the root controller's view, the modal controllers sit on top, so do the popover controllers.
If I present the cover view modally and there is already a modal controller, only part of the screen is covered.

Advantages, problems, examples of adding another UIWindow to an iOS app?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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最近我一直在想一个事实，一个iOS应用程序只有一个UIWindow。创建另一个UIWindow并将其放在屏幕上似乎不是问题。我的问题有点模糊，但我感兴趣的是：使用第二个UIWindow可以实现哪些其他方式无法实现的目标？使用多个UIWindow实例时会出现什么问题？我看到人们使用第二个UIWindow在iPhone上显...

问向iOS应用程序添加另一个UIWindow的优点、问题和示例？
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