The default implementation of this method does nothing on iOS 5.1 and earlier. Otherwise, the default implementation uses any constraints you have set to determine the size and position of any subviews.
iOS - layoutSubviews总结(作用及调用机制)iOS layout机制相关方法 layoutSubviews在以下情况下会被调用: 1、init初始化不会触发layoutSubviews但是是用initWithFrame...