问题
I have a UIViewController object in a .xib file. I add a UIImageView to it, and then try to add a button as a subview of the UIImageView. It instead replaces the UIImageView. It works fine if both are subviews of a UIView. What gives? I thought this would work since UIImageView is a subclass of UIView?
回答1:
Only Apple knows.
However, look at here for a workaround:
Apple Interface Builder: adding subview to UIImageView
回答2:
A UIImageView is it's own object and a UIButton is its own object. A UIImageView is an outlet placeholder for an image. If you're trying to add a background image to a button you can use the background image property or if you'd like the background to span beyond the bounds of the button you can drop a UIView onto IB and style that using code or subclassing UIImageView.
来源：https://stackoverflow.com/questions/4892770/add-a-subview-to-a-uiimageview-that-is-the-view-outlet-of-a-uiviewcontroller-in