In iOS, the developer can get the current device language and locale. However, what if we want to set the keyboard to a specific language/locale, based on the users' preferences, when they are in different parts of our app? In my app, there are multiple languages, and I want the user to be presented with the Arabic keyboard, for example, when they are in the Arabic section, and the Russian keyboard, for example, when they are in the Russian section. How is it possible to pull this off?
This capability is not in the API. You'll have to build your own custom keyboard
来源：https://stackoverflow.com/questions/5073254/how-to-change-ios-device-keyboard-to-specific-language