问题
I'd like to detect whether or not the keyboard is showing. I've found a few other posts that traverse the subviews of UIWindow to find the keyboard, but if that is the only way then I'll figure out something else. I suppose I could also observe the UIKeyboard notifications, but I'm guessing there is a cleaner solution out there.
回答1:
I am not sure what's "dirty" in observing UIKeyboard notifications but it definitely beats traversing UIWindow hierarchy.
来源：https://stackoverflow.com/questions/3903987/detect-if-uikeyboard-is-showing