问题
In our app, we set the keyboardAppearance to dark. This produces a black keyboard, as expected. However, if the keyboard is showing, and we press the home button, and then go back into the app, the keyboard turns white, as shown. Any ideas why?
回答1:
It may have todo with the fact that the keyboard is a global object. There's only ever one keyboard in memory at any given time. Also, the OS will automatically change the keyboard color based on the background. Therefore, your setting is probably just getting overridden. I would suggest hiding the keyboard when your app enters the background, and then re-show it when it re-enters the foreground. Then when you re-show the keyboard reset the keyboard appearance via code.
来源：https://stackoverflow.com/questions/28114505/ios-keyboard-colour-changes-keyboardappearance-dark-color-doesnt-stick