SVProgressHUD
GitHub地址：https://github.com/TransitApp/SVProgressHUD
SVProgressHUD和MBProgressHUD效果差不多，特点就是不需要使用协议，同时也不需要声明实例。直接通过类方法就可以调用：
[SVProgressHUD method]
[SVProgressHUD dismiss]
加载环
基本方法
+ (void)show; 显示:状态是一个迅速转动的圈
+ (void)showWithMaskType:(SVProgressHUDMaskType)maskType; 显示并且带着一个状态
+ (void)showWithStatus:(NSString*)status; 显示并且带着文字
+ (void)showWithStatus:(NSString*)status maskType:(SVProgressHUDMaskType)maskType;
+ (void)showProgress:(float)progress; //显示进度:状态是一个进度圈
+ (void)showProgress:(float)progress maskType:(SVProgressHUDMaskType)maskType;
+ (void)showProgress:(float)progress status:(NSString*)status;
+ (void)showProgress:(float)progress status:(NSString*)status maskType:(SVProgressHUDMaskType)maskType;
+ (void)setStatus:(NSString*)string; // 改变正显示着的HUD的文字
// stops the activity indicator, shows a glyph + status, and dismisses HUD a little bit later
+ (void)showInfoWithStatus:(NSString *)string; //显示消息信息，其实就是中心图片更换了
+ (void)showInfoWithStatus:(NSString *)string maskType:(SVProgressHUDMaskType)maskType;
+ (void)showSuccessWithStatus:(NSString*)string; //显示成功消息
+ (void)showSuccessWithStatus:(NSString*)string maskType:(SVProgressHUDMaskType)maskType;
+ (void)showErrorWithStatus:(NSString *)string; //显示错误消息
+ (void)showErrorWithStatus:(NSString *)string maskType:(SVProgressHUDMaskType)maskType;
// use 28x28 white pngs
+ (void)showImage:(UIImage*)image status:(NSString*)status; //显示自己设置的图片,图片大小事28 * 28 px
+ (void)showImage:(UIImage*)image status:(NSString*)status maskType:(SVProgressHUDMaskType)maskType;
+ (void)setOffsetFromCenter:(UIOffset)offset; //距离中心点的偏移量
+ (void)resetOffsetFromCenter; //返回中心点
+ (void)popActivity; // 消除一个HUD，根据其实现方法如果前面有执行了好几次show方法，如果给定的progress == 0 或者 pregress < 0那样就会让使一个参数+1，执行这个方法会使那个参数-1，如果参数==0时 执行dismiss方法。
+ (void)dismiss; 消失
+ (BOOL)isVisible; 是否正在显示
关于HUD的属性配置
+ (void)setBackgroundColor:(UIColor*)color; //背景颜色 // default is [UIColor whiteColor]
+ (void)setForegroundColor:(UIColor*)color; //progress 和 label颜色 // default is [UIColor blackColor]
+ (void)setRingThickness:(CGFloat)width; //progress 宽度 // default is 4 pt
+ (void)setFont:(UIFont*)font; //字体 // default is [UIFont preferredFontForTextStyle:UIFontTextStyleSubheadline]
+ (void)setInfoImage:(UIImage*)image; //消息的图片 // default is the bundled info image provided by Freepik
+ (void)setSuccessImage:(UIImage*)image; //成功时的图片 // default is the bundled success image provided by Freepik
+ (void)setErrorImage:(UIImage*)image; //失败时的图片 // default is the bundled error image provided by Freepik
+ (void)setDefaultMaskType:(SVProgressHUDMaskType)maskType; //当HUD显示时，用户是否可以点击其他控件// default is SVProgressHUDMaskTypeNone
SVProgressHUDMaskTypeNone = 1, // 允许用户进行其他用户操作
SVProgressHUDMaskTypeClear, // 不允许用户进行其他用户操作
SVProgressHUDMaskTypeBlack, // 不允许用户进行其他用户操作，并且背景是黑色的
SVProgressHUDMaskTypeGradient // 允许用户进行其他用户操作，并且背景是渐变的黑色
+ (void)setViewForExtension:(UIView*)view; //可以延展一个图片必须设置#define SV_APP_EXTENSIONS
关于HUD的通知
extern NSString * const SVProgressHUDDidReceiveTouchEventNotification; //在HUD外点击
extern NSString * const SVProgressHUDDidTouchDownInsideNotification; //在HUD中点击
extern NSString * const SVProgressHUDWillDisappearNotification; //将要显示
extern NSString * const SVProgressHUDDidDisappearNotification; //已经显示
extern NSString * const SVProgressHUDWillAppearNotification; //将要消失
extern NSString * const SVProgressHUDDidAppearNotification; //已经消失
extern NSString * const SVProgressHUDStatusUserInfoKey; //HUD的状态
在通知中userInfo字典中存储了HUD的状态，其key为SVProgressHUDStatusUserInfoKey
整理自：
https://www.jianshu.com/p/5750c72074a7
https://www.jianshu.com/p/1ec4dca92e71
