问题
If I start a Voice Memo on iOS 8, and go to another app (e.g. Notes) then a red notice appears on the top of the screen (see below, "Recording 00:16").
What is the name of this notice? Where is the relevant iOS documentation?
回答1:
You are talking about double-high status bar, this is caused when some other app is recording audio , fetching background locations , etc in background , the double height status bar suggests user that the app is using the resource.
You can find relevant docs here
Make sure your UI can handle the double-high status bar. The double-high status bar appears during events such as in-progress phone calls, audio recording, and tethering. In unprepared apps the extra height of this bar can cause layout problems. For example, the UI can become pushed down or covered. In a multitasking environment, it’s especially important to be able to handle the double-high status bar properly because there are likely to be more apps that can cause it to appear.
来源：https://stackoverflow.com/questions/29485114/what-is-the-name-of-this-background-app-notice