关于UIView的autoresizingMask属性的研究

UIViewAutoresizingNone                 = 0,
UIViewAutoresizingFlexibleLeftMargin   = 1 << 0,
UIViewAutoresizingFlexibleWidth        = 1 << 1,
UIViewAutoresizingFlexibleRightMargin  = 1 << 2,
UIViewAutoresizingFlexibleTopMargin    = 1 << 3,
UIViewAutoresizingFlexibleHeight       = 1 << 4,
UIViewAutoresizingFlexibleBottomMargin = 1 << 5

UIViewAutoresizingNone：控件相对于父视图坐标值不变；

UIViewAutoresizingFlexibleWidth：控件的宽度随着父视图的宽度按比例改变；

例如：label宽度为100，屏幕的宽度为320。当屏幕宽度为480时，label宽度变为100*480/320

UIViewAutoresizingFlexibleHeight：与UIViewAutoresizingFlexibleWidth相同

UIViewAutoresizingFlexibleLeftMargin：到屏幕左边的距离随着父视图的宽度按比例改变；

例如：CGRectMake(50, 100, 200, 40)]; 当屏幕的宽度为320，x为50；当屏幕宽度为480时，labelx坐标变为 50*480/320。控件坐标变为 CGRectMake(75, 100, 200, 40)];

UIViewAutoresizingFlexibleRightMargin、UIViewAutoresizingFlexibleTopMargin、UIViewAutoresizingFlexibleBottomMargin与UIViewAutoresizingFlexibleLeftMargin类似