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總結(作用及調用機制)iOS layout機制相關方法 layoutSubviews在以下情況下會被調用: 1索昂、init初始化不會觸發(fā)layoutSubviews但是是用initWithFrame...