UIButton头文件学习

UIButtonType枚举：

    UIButtonTypeCustom                               自定义按钮类型

    UIButtonTypeSystem NS_ENUM_AVAILABLE_IOS(7_0),   系统按钮类型

    UIButtonTypeDetailDisclosure,                    蓝色小箭头按钮              

    UIButtonTypeInfoLight,                          
亮色感叹号                        

    UIButtonTypeInfoDark,                            暗色感叹号

    UIButtonTypeContactAdd,                          十字加号按钮

    UIButtonTypeRoundedRect = UIButtonTypeSystem,    已过时，使用UIButtonTypeSystem替代
UIButton继承体系：

          UIButton -> UIControl ->UIView

常用的属性：

@property(nonatomic) 
        UIEdgeInsets contentEdgeInsets
UI_APPEARANCE_SELECTOR;  
按钮内容间距

@property(nonatomic)         
UIEdgeInsets titleEdgeInsets;                            按钮标题间距   

@property(nonatomic)         
BOOL         reversesTitleShadowWhenHighlighted;         标题的阴影改变时，按钮是否高亮显示。默认为NO

@property(nonatomic)         
UIEdgeInsets imageEdgeInsets;                            按钮图片间距

@property(nonatomic)         
BOOL         adjustsImageWhenHighlighted;                按钮高亮的情况下，图像的颜色是否要加深一点。默认是YES

@property(nonatomic)         
BOOL         adjustsImageWhenDisabled;                   按钮禁用的情况下，图像的颜色是否要加深一点。默认是YES

@property(nonatomic)         
BOOL         showsTouchWhenHighlighted
__TVOS_PROHIBITED;按下按钮是否会发光。默认是NO

设置按钮不同状态下外观的一系列方法（set）：

- (void)setTitle:(nullable
NSString *)title forState:(UIControlState)state;                    
// default is nil. title is assumed to be single line

- (void)setTitleColor:(nullable
UIColor *)color forState:(UIControlState)state
UI_APPEARANCE_SELECTOR;
// default if nil. use opaque white

- (void)setTitleShadowColor:(nullable
UIColor *)color forState:(UIControlState)state
UI_APPEARANCE_SELECTOR;
// default is nil. use 50% black

- (void)setImage:(nullable
UIImage *)image forState:(UIControlState)state;                     
// default is nil. should be same size if different for different states

- (void)setBackgroundImage:(nullable
UIImage *)image forState:(UIControlState)state
UI_APPEARANCE_SELECTOR;
// default is nil

- (void)setAttributedTitle:(nullable
NSAttributedString *)title forState:(UIControlState)state
NS_AVAILABLE_IOS(6_0);
// default is nil. title is assumed to be single line

获取按钮不同状态下外观的一系列方法（get）

- (nullable
NSString *)titleForState:(UIControlState)state;         
// these getters only take a single state value

- (nullable UIColor *)titleColorForState:(UIControlState)state;

- (nullable UIColor *)titleShadowColorForState:(UIControlState)state;

- (nullable UIImage *)imageForState:(UIControlState)state;

- (nullable UIImage *)backgroundImageForState:(UIControlState)state;

- (nullable NSAttributedString *)attributedTitleForState:(UIControlState)state
NS_AVAILABLE_IOS(6_0);

获取按钮当前状态下的一系列属性（get）

@property(nullable,
nonatomic,readonly,strong)
NSString *currentTitle;            
// normal/highlighted/selected/disabled. can return nil

@property(nonatomic,readonly,strong)
UIColor  *currentTitleColor;       
// normal/highlighted/selected/disabled. always returns non-nil. default is white(1,1)

@property(nullable,
nonatomic,readonly,strong)
UIColor  *currentTitleShadowColor; 
// normal/highlighted/selected/disabled.

@property(nullable,
nonatomic,readonly,strong)
UIImage  *currentImage;            
// normal/highlighted/selected/disabled. can return nil

@property(nullable,
nonatomic,readonly,strong)
UIImage  *currentBackgroundImage;  
// normal/highlighted/selected/disabled. can return nil

@property(nullable,
nonatomic,readonly,strong)
NSAttributedString *currentAttributedTitle
NS_AVAILABLE_IOS(6_0); 
// normal/highlighted/selected/disabled. can return nil