SVProgressHUD源码解读(2.0.3)

SVProgressHUD是iOS开发中比较常用的一个三方库，用来在执行耗时操作或者指示用户操作结果的场合，由于使用简单，功能丰富，交互友好，被广泛应用。本文从源码的角度，解读一下实现的过程，希望能起到抛砖引玉的作用。

一. 效果预览

1. SVPIndefiniteAnimatedView

2. SVProgressAnimatedView

3. SVRadialGradientLayer

二. 类分析

1. SVProgressHUD

这是SVProgressHUD显示提示框的类，提供类方法和属性来进行不同的设置。

** HUD提示框背景

typedef NS_ENUM(NSInteger, SVProgressHUDStyle) {
	SVProgressHUDStyleLight, // 白色
	SVProgressHUDStyleDark, // 黑色
	SVProgressHUDStyleCustom // 用户自定义
};

** 遮罩层背景

typedef NS_ENUM(NSUInteger, SVProgressHUDMaskType) {
	SVProgressHUDMaskTypeNone = 1, // 默认mask，用户和交互
	SVProgressHUDMaskTypeClear, // 不允许交互
	SVProgressHUDMaskTypeBlack, // 不允许交互，遮罩层呈黑色部分透明
	SVProgressHUDMaskTypeGradient, // 不允许交互，遮罩层呈渐变效果
	SVProgressHUDMaskTypeCustom // 不允许交互，遮罩层颜色自定义
};

** 无限循环的显示类型

typedef NS_ENUM(NSUInteger, SVProgressHUDAnimationType) {
	SVProgressHUDAnimationTypeFlat, // SVPIndefiniteAnimatedView
	SVProgressHUDAnimationTypeNative // 系统的UIActivityIndicatorView
};

**常用属性介绍

hud最小尺寸，默认是（100，100）

@property (assign, nonatomic) CGSize minimumSize UI_APPEARANCE_SELECTOR;

圆环厚度，默认是2px

@property (assign, nonatomic) CGFloat ringThickness UI_APPEARANCE_SELECTOR;

圆环半径，默认是18px

@property (assign, nonatomic) CGFloat ringRadius UI_APPEARANCE_SELECTOR;

提示语字体，默认是14px

@property (strong, nonatomic) UIFont *font UI_APPEARANCE_SELECTOR;

Image提示框显示时间，默认是5s

@property (assign, nonatomic) NSTimeInterval minimumDismissTimeInterval;

** 常用方法介绍

• 无限循环状态显示，不会自动小时，需主动调用dismiss方法

+ (void)show;
+ (void)showWithStatus:(NSString*)status;

+ (void)dismiss;
+ (void)dismissWithCompletion:(SVProgressHUDDismissCompletion)completion;
+ (void)dismissWithDelay:(NSTimeInterval)delay;
+ (void)dismissWithDelay:(NSTimeInterval)delay completion:(SVProgressHUDDismissCompletion)completion;

• 进度条状态显示

+ (void)showProgress:(float)progress;
+ (void)showProgress:(float)progress status:(NSString*)status;

• 图片状态显示

+ (void)showInfoWithStatus:(NSString*)status;
+ (void)showSuccessWithStatus:(NSString*)status;
+ (void)showErrorWithStatus:(NSString*)status;

• hud距离中心点的偏移量

+ (void)setOffsetFromCenter:(UIOffset)offset;
+ (void)resetOffsetFromCenter;

** 通知

通过监听不同的通知事件，可以获取hud的状态

extern NSString * const SVProgressHUDWillDisappearNotification;
extern NSString * const SVProgressHUDDidDisappearNotification;
extern NSString * const SVProgressHUDWillAppearNotification;
extern NSString * const SVProgressHUDDidAppearNotification;

** hud显示流程

SVProgressHUD采用单例模式，简化代码维护；同时，根据SVProgressHUD的层级结构可以看出，从底层到顶层依次是：UIControl (overlayView) -> SVProgressHUD -> UIView (hudView) -> UIVisualEffectView -> AnimatedView (具体动画视图) 。

• -(void)showStatus:(NSString*)status, 这是显示无限循环状态的提示框，可以添加文字进一步详细补充。其中，SVProgressHUD采用图形和文字分离的模式，方面文字视图的复用。所有，显示文字的视图，最终都会调用下面的方法。

- (void)showStatus:(NSString*)status {
    // 更新frame及位置，因为frame是更加status来确定的而postion是根据参数控制的。
    [self updateHUDFrame];
    [self positionHUD:nil];

    // 更新 accesibilty 和是否可以点击
    if(self.defaultMaskType != SVProgressHUDMaskTypeNone) {
        self.accessibilityLabel = status;
        self.isAccessibilityElement = YES;
    } else {
        self.hudView.accessibilityLabel = status;
        self.hudView.isAccessibilityElement = YES;
    }

    // Show if not already visible
    // Checking one alpha value is sufficient as they are all the same
#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 80000
    if(self.hudView.contentView.alpha != 1.0f){
#else
	 根据alpha值判断是是否可见
    if(self.hudView.alpha != 1.0f){
#endif
        // 如果之前不可见则发出SVProgressHUDWillAppearNotification通知，告诉马上显示
        [[NSNotificationCenter defaultCenter] postNotificationName:SVProgressHUDWillAppearNotification
                                                            object:self
                                                          userInfo:[self notificationUserInfo]];

        //缩放效果
        self.hudView.transform = CGAffineTransformScale(self.hudView.transform, 1.3, 1.3);

        // Activate blur on view before animation on older iOS versions,
        // as we cannot animate this property and use alpha values instead
#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 80000
        bool greateriOS9 = kCFCoreFoundationVersionNumber >= kCFCoreFoundationVersionNumber_iOS_9_0;
        if (self.defaultStyle != SVProgressHUDStyleCustom && !greateriOS9) {
            [self addBlur];

            // Update alpha
            self.hudView.contentView.alpha = 1.0f;
        }
#endif

        // Define blocks
        __block void (^animationsBlock)(void) = ^{
            // Shrink HUD to finish pop up animation
            self.hudView.transform = CGAffineTransformScale(self.hudView.transform, 1/1.3f, 1/1.3f);

#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 80000
            if(self.defaultStyle != SVProgressHUDStyleCustom && greateriOS9){
                // Fade in blur effect
                [self addBlur];

                // Update alpha
                self.hudView.contentView.alpha = 1.0f;
            } else {
                // This gives a warning on iOS 8, however it works, see #703
                self.hudView.alpha = 1.0f;
            }
#else
            self.hudView.alpha = 1.0f;
            self.hudView.contentView.alpha = 1.0f;
#endif
            self.backgroundView.alpha = 1.0f;
        };

        __block void (^completionBlock)(void) = ^{
            // Check if we really achieved to show the HUD (<=> alpha values are applied)
            // and the change of these values has not been cancelled in between e.g. due to a dismissal
            // Checking one alpha value is sufficient as they are all the same
#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 80000
            if(self.hudView.contentView.alpha == 1.0f){
#else
            if(self.hudView.alpha == 1.0f){
#endif
                // Register observer <=> we now have to handle orientation changes etc.
                [self registerNotifications];

                // Post notification to inform user
                [[NSNotificationCenter defaultCenter] postNotificationName:SVProgressHUDDidAppearNotification
                                                                    object:self
                                                                  userInfo:[self notificationUserInfo]];
            }

            // 更新 accesibilty
            UIAccessibilityPostNotification(UIAccessibilityScreenChangedNotification, nil);
            UIAccessibilityPostNotification(UIAccessibilityAnnouncementNotification, status);
        };

        if (self.fadeInAnimationDuration > 0) {
            // 如果设置了动画时间则进行动画效果
            [UIView animateWithDuration:self.fadeInAnimationDuration
                                  delay:0
                                options:(UIViewAnimationOptions) (UIViewAnimationOptionAllowUserInteraction | UIViewAnimationCurveEaseIn | UIViewAnimationOptionBeginFromCurrentState)
                             animations:^{
                                 animationsBlock();
                             } completion:^(BOOL finished) {
                                 completionBlock();
                             }];
        } else {
            animationsBlock();
            completionBlock();
        }

        // 完成了更新视图层次，视图的frame以及视图的各种属性之后，告诉系统稍微进行重绘
        [self setNeedsDisplay];
    }
}

• -(void)showProgress:(float)progress status:(NSString*)status，这是显示单次滚动效果的提示框，每次显示视图前，都会取消其它视图，防止上次显示不同视图产生的干扰。其中，在设置strokeEnd时，使用事物类CATransaction，确保操作不被干扰。

- (void)showProgress:(float)progress status:(NSString*)status {
    __weak SVProgressHUD *weakSelf = self;
    [[NSOperationQueue mainQueue] addOperationWithBlock:^{
        __strong SVProgressHUD *strongSelf = weakSelf;
        if(strongSelf){
            // 更新并且检查视图层次确保SVProgressHUD可见
            [strongSelf updateViewHierarchy];

            // 重置imageView和消失时间。防止之前调用过，使用上次存在的样式设置
            strongSelf.imageView.hidden = YES;
            strongSelf.imageView.image = nil;

            if(strongSelf.fadeOutTimer) {
                strongSelf.activityCount = 0;
            }
            strongSelf.fadeOutTimer = nil;

            // 更新statusLabel显示的内容和显示的进度
            strongSelf.statusLabel.text = status;
            strongSelf.progress = progress;

            //根据progersss的值来确定正确的样式，当progress>=0的时候，显示进度样式，当progress = -1的时候为无限旋转的样式
            if(progress >= 0) {
                // 防止上次为无限旋转的样式导致重叠
                [strongSelf cancelIndefiniteAnimatedViewAnimation];

                // 添加进度视图到hudview上，并且设置当前进度值
                if(!strongSelf.ringView.superview){
#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 80000
                    [strongSelf.hudVibrancyView.contentView addSubview:strongSelf.ringView];
#else
                    [strongSelf.hudView addSubview:strongSelf.ringView];
#endif
                }
                if(!strongSelf.backgroundRingView.superview){
#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 80000
                    [strongSelf.hudVibrancyView.contentView addSubview:strongSelf.backgroundRingView];
#else
                    [strongSelf.hudView addSubview:strongSelf.backgroundRingView];
#endif
                }

                // Set progress animated
                [CATransaction begin];
                [CATransaction setDisableActions:YES];
                strongSelf.ringView.strokeEnd = progress;
                [CATransaction commit];

                // 更新activityCount
                if(progress == 0) {
                    strongSelf.activityCount++;
                }
            } else {
                // 防止上次为进度的样式导致重叠
                [strongSelf cancelRingLayerAnimation];

                // 增加无限旋转视图到hudview上
#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 80000
                [strongSelf.hudVibrancyView.contentView addSubview:strongSelf.indefiniteAnimatedView];
#else
                [strongSelf.hudView  addSubview:strongSelf.indefiniteAnimatedView];
#endif
                if([strongSelf.indefiniteAnimatedView respondsToSelector:@selector(startAnimating)]) {
                    [(id)strongSelf.indefiniteAnimatedView startAnimating];
                }

                // Update the activity count
                strongSelf.activityCount++;
            }

            // 显示提示的文字信息
            [strongSelf showStatus:status];

            // Tell the Haptics Generator to prepare for feedback, which may come soon
#if TARGET_OS_IOS && __IPHONE_OS_VERSION_MAX_ALLOWED >= 100000
            [strongSelf.hapticGenerator prepare];
#endif
        }
    }];
}

• -(void)showImage:(UIImage*)image status:(NSString*)status duration:(NSTimeInterval)duration，这是显示带Image的提示框，自带info/success/error三种类型，也可以自定义图片。

- (void)showImage:(UIImage*)image status:(NSString*)status duration:(NSTimeInterval)duration {
    __weak SVProgressHUD *weakSelf = self;
    [[NSOperationQueue mainQueue] addOperationWithBlock:^{
        __strong SVProgressHUD *strongSelf = weakSelf;
        if(strongSelf){
            // 更新并且检查视图层次确保SVProgressHUD可见
            [strongSelf updateViewHierarchy];

            // 重置progress，并取消其它动画
            strongSelf.progress = SVProgressHUDUndefinedProgress;
            [strongSelf cancelRingLayerAnimation];
            [strongSelf cancelIndefiniteAnimatedViewAnimation];

            // 更新imageView
            UIColor *tintColor = strongSelf.foregroundColorForStyle;
            UIImage *tintedImage = image;
            if (image.renderingMode != UIImageRenderingModeAlwaysTemplate) {
                tintedImage = [image imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
            }
            strongSelf.imageView.tintColor = tintColor;
            strongSelf.imageView.image = tintedImage;
            strongSelf.imageView.hidden = NO;

            // 更新文字
            strongSelf.statusLabel.text = status;

            // 显示文字视图
            [strongSelf showStatus:status];

            // An image will be dismissed automatically. Therefore, we start a timer
            // which then will call dismiss after the predefined duration
            // 添加定时消失timer
            strongSelf.fadeOutTimer = [NSTimer timerWithTimeInterval:duration target:strongSelf selector:@selector(dismiss) userInfo:nil repeats:NO];
            [[NSRunLoop mainRunLoop] addTimer:strongSelf.fadeOutTimer forMode:NSRunLoopCommonModes];
        }
    }];
}

**其它方法

• 设置hud位置的方法

- (void)positionHUD:(NSNotification*)notification

• 调整hud尺寸的方法

- (void)updateHUDFrame

• 更新模糊背景视图的方法

- (void)updateBlurBounds

2. SVPIndefiniteAnimatedView 类

这个类提供了一个无线旋转的动画，实现方法是把一个颜色渐变的图片旋转，然后利用UIBezierPath/CAShapeLayer/Mask等遮住不需要的部分，最后利用CABasicAnimation设置无限旋转动画。其中，核心部分是利用layer的mask属性实现遮罩功能，而mask的实现方法是显示显示bounds的非透明部分，实例图如下：

3. SVProgressAnimatedView 类

这个类提供一个画圆环的视图，通过不断改变layer的strokeEnd的值，实现了进度的显示。顺便提一下，storkeStart使用的默认值是0, 所以是从正上方开始的。

- (void)setStrokeEnd:(CGFloat)strokeEnd {
	_strokeEnd = strokeEnd;
	_ringAnimatedLayer.strokeEnd = _strokeEnd;
}

4. SVRadialGradientLayer 类

这个类继承自CALayer，通过CGContextDrawRadialGradient来画渐变颜色层；其中，CoreFoundation中通过create创建的需要用release释放，否则会造成内存泄漏。

至此，SVProgressHUD分析暂告一段落，分析的不全面的地方，欢迎交流。

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参考资料

https://github.com/SVProgressHUD/SVProgressHUD

http://www.jianshu.com/p/a08d4597cf24