UIView.h解读

autoresizingMask

定义:

@property(nonatomic) UIViewAutoresizing autoresizingMask;    // simple resize. default is UIViewAutoresizingNone

autoresizingMask是一个integer bit遮罩,决定了当父控件的bounds发生改变时,控件如何改变自己的尺寸
是一个枚举类型,有7种取值:

typedef NS_OPTIONS(NSUInteger, UIViewAutoresizing) {    UIViewAutoresizingNone                 = 0,    UIViewAutoresizingFlexibleLeftMargin   = 1 << 0,    UIViewAutoresizingFlexibleWidth        = 1 << 1,    UIViewAutoresizingFlexibleRightMargin  = 1 << 2,    UIViewAutoresizingFlexibleTopMargin    = 1 << 3,    UIViewAutoresizingFlexibleHeight       = 1 << 4,    UIViewAutoresizingFlexibleBottomMargin = 1 << 5};

1. UIViewAutoresizingNone控件不改变尺寸.
2. UIViewAutoresizingFlexibleLeftMargin 扩大或缩小左边间距
3. UIViewAutoresizingFlexibleWidth扩大或缩小控件的宽度
4. UIViewAutoresizingFlexibleRightMargin 扩大或缩小控件的右边边距.
5. UIViewAutoresizingFlexibleTopMargin扩大或缩小控件的顶部边距.
6. UIViewAutoresizingFlexibleHeight扩大或缩小控件的高度
7. UIViewAutoresizingFlexibleBottomMargin扩大或缩小控件的底部边距.