UIControlState
typedef NS_OPTIONS(NSUInteger, UIControlState) {
UIControlStateNormal = 0, //控件的正常或默认状态 ,即已启用但未选中也未突出显示
UIControlStateHighlighted = 1 << 0, // used when UIControl isHighlighted is set 突出显示控件的状态 俗称高亮
UIControlStateDisabled = 1 << 1, //禁用控件状态
UIControlStateSelected = 1 << 2, // flag usable by app (see below)选择控件的状态
UIControlStateFocused NS_ENUM_AVAILABLE_IOS(9_0) = 1 << 3, // Applicable only when the screen supports focus获得焦点状态
UIControlStateApplication = 0x00FF0000, // additional flags available for application use附加的控制状态标志可供应用程序使用
UIControlStateReserved = 0xFF000000 // flags reserved for internal framework use内部框架使用保留的控制状态
};