UIButton

typedef NS_OPTIONS(NSUInteger, UIControlState) {

    UIControlStateNormal        = 0,                             //常态 

    UIControlStateHighlighted  = 1 << 0,                    // used when UIControl isHighlighted is set 高亮

    UIControlStateDisabled      = 1 << 1,                    //禁用

    UIControlStateSelected      = 1 << 2,                    // flag usable by app (see below) 选中

    UIControlStateApplication  = 0x00FF0000,             // additional flags available for application use  当应用程序标志使用时

    UIControlStateReserved     = 0xFF000000              // flags reserved for internal framework use  为内部框架预留的

};