将子视图添加到UIImageView，它是IB中UIViewController的视图出口
问题描述：
我在.xib文件中有一个UIViewController对象。我添加了一个UIImageView，然后尝试添加一个按钮作为UIImageView的子视图。它取代了UIImageView。如果两者都是UIView的子视图，它工作正常。是什么赋予了？我认为这可行，因为UIImageView是UIView的子类？
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?
答
只有Apple知道。
但是，请看这里找一个解决方法：
However, look at here for a workaround: