YYKit源码探究（十八） —— UIImageView分类之highlight image部分（二）

版本记录

版本号	时间
V1.0	2018.03.25

前言

iOS圈内有几个人大家基本都知道，比如说王巍、唐巧，还有YYKit框架的作者现任职于滴滴的郭曜源 - ibireme等。这里有一篇唐巧对他的专访，还有他的 GitHub - Yaoyuan 和 博客，这里贴出来框架YYKit 框架。接下来几篇我们就一起来看一下这个框架。感兴趣的可以看上面写的几篇。
1. YYKit源码探究（一） —— 基本概览
2. YYKit源码探究（二） —— NSString分类之Hash（一）
3. YYKit源码探究（三） —— NSString分类之Encode and decode（二）
4. YYKit源码探究（四） —— NSString分类之Drawing（三）
5. YYKit源码探究（五） —— NSString分类之Regular Expression（四）
6. YYKit源码探究（六） —— NSString分类之NSNumber Compatible（五）
7. YYKit源码探究（七） —— NSString分类之Utilities（六）
8. YYKit源码探究（八） —— NSNumber分类（一）
9. YYKit源码探究（九） —— UIFont分类之架构分析和Font Traits（一）
10. YYKit源码探究（十） —— UIFont分类之Create font（二）
11. YYKit源码探究（十一） —— UIFont分类之Load and unload font（三）
12. YYKit源码探究（十二） —— UIFont分类之Dump font data（四）
13. YYKit源码探究（十三） —— UIImage分类之框架结构和Create image部分（一）
14. YYKit源码探究（十四） —— UIImage分类之Image Info（二）
15. YYKit源码探究（十五） —— UIImage分类之Modify Image（三）
16. YYKit源码探究（十六） —— UIImage分类之Image Effect（四）
17. YYKit源码探究（十七） —— UIImageView分类之架构和image部分（一）

回顾

上一篇主要介绍了UIImageView分类之架构和image部分，这一篇主要看一下highlight image部分。

---

API

下面我们看一下API。

#pragma mark - highlight image

/**
 Current highlighted image URL.
 
 @discussion Set a new value to this property will cancel the previous request
 operation and create a new request operation to fetch image. Set nil to clear
 the highlighted image and image URL.
 */
@property (nullable, nonatomic, strong) NSURL *highlightedImageURL;

/**
 Set the view's `highlightedImage` with a specified URL.
 
 @param imageURL    The image url (remote or local file path).
 @param placeholder The image to be set initially, until the image request finishes.
 */
- (void)setHighlightedImageWithURL:(nullable NSURL *)imageURL placeholder:(nullable UIImage *)placeholder;

/**
 Set the view's `highlightedImage` with a specified URL.
 
 @param imageURL The image url (remote or local file path).
 @param options  The options to use when request the image.
 */
- (void)setHighlightedImageWithURL:(nullable NSURL *)imageURL options:(YYWebImageOptions)options;

/**
 Set the view's `highlightedImage` with a specified URL.
 
 @param imageURL    The image url (remote or local file path).
 @param placeholder The image to be set initially, until the image request finishes.
 @param options     The options to use when request the image.
 @param completion  The block invoked (on main thread) when image request completed.
 */
- (void)setHighlightedImageWithURL:(nullable NSURL *)imageURL
                          placeholder:(nullable UIImage *)placeholder
                              options:(YYWebImageOptions)options
                           completion:(nullable YYWebImageCompletionBlock)completion;

/**
 Set the view's `highlightedImage` with a specified URL.
 
 @param imageURL    The image url (remote or local file path).
 @param placeholder The image to be set initially, until the image request finishes.
 @param options     The options to use when request the image.
 @param progress    The block invoked (on main thread) during image request.
 @param transform   The block invoked (on background thread) to do additional image process.
 @param completion  The block invoked (on main thread) when image request completed.
 */
- (void)setHighlightedImageWithURL:(nullable NSURL *)imageURL
                          placeholder:(nullable UIImage *)placeholder
                              options:(YYWebImageOptions)options
                             progress:(nullable YYWebImageProgressBlock)progress
                            transform:(nullable YYWebImageTransformBlock)transform
                           completion:(nullable YYWebImageCompletionBlock)completion;

/**
 Set the view's `highlightedImage` with a specified URL.
 
 @param imageURL    The image url (remote or local file path).
 @param placeholder he image to be set initially, until the image request finishes.
 @param options     The options to use when request the image.
 @param manager     The manager to create image request operation.
 @param progress    The block invoked (on main thread) during image request.
 @param transform   The block invoked (on background thread) to do additional image process.
 @param completion  The block invoked (on main thread) when image request completed.
 */
- (void)setHighlightedImageWithURL:(nullable NSURL *)imageURL
                          placeholder:(nullable UIImage *)placeholder
                              options:(YYWebImageOptions)options
                              manager:(nullable YYWebImageManager *)manager
                             progress:(nullable YYWebImageProgressBlock)progress
                            transform:(nullable YYWebImageTransformBlock)transform
                           completion:(nullable YYWebImageCompletionBlock)completion;

/**
 Cancel the current highlighed image request.
 */
- (void)cancelCurrentHighlightedImageRequest;

这个API文档和上一篇都是类似的，这里不同的是这个是高亮状态，那么只给出第一个和最后一个方法的实现吧。

1. - (void)setHighlightedImageWithURL:(nullable NSURL *)imageURL placeholder:(nullable UIImage *)placeholder;

该方法的作用就是根据给定的URL设置下载的图片。

方法实现

- (void)setHighlightedImageWithURL:(NSURL *)imageURL placeholder:(UIImage *)placeholder {
    [self setHighlightedImageWithURL:imageURL
                         placeholder:placeholder
                             options:kNilOptions
                             manager:nil
                            progress:nil
                           transform:nil
                          completion:nil];
}

- (void)setHighlightedImageWithURL:(NSURL *)imageURL
                       placeholder:(UIImage *)placeholder
                           options:(YYWebImageOptions)options
                           manager:(YYWebImageManager *)manager
                          progress:(YYWebImageProgressBlock)progress
                         transform:(YYWebImageTransformBlock)transform
                        completion:(YYWebImageCompletionBlock)completion {
    if ([imageURL isKindOfClass:[NSString class]]) imageURL = [NSURL URLWithString:(id)imageURL];
    manager = manager ? manager : [YYWebImageManager sharedManager];
    
    _YYWebImageSetter *setter = objc_getAssociatedObject(self, &_YYWebImageHighlightedSetterKey);
    if (!setter) {
        setter = [_YYWebImageSetter new];
        objc_setAssociatedObject(self, &_YYWebImageHighlightedSetterKey, setter, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    }
    int32_t sentinel = [setter cancelWithNewURL:imageURL];
    
    dispatch_async_on_main_queue(^{
        if ((options & YYWebImageOptionSetImageWithFadeAnimation) &&
            !(options & YYWebImageOptionAvoidSetImage)) {
            if (self.highlighted) {
                [self.layer removeAnimationForKey:_YYWebImageFadeAnimationKey];
            }
        }
        if (!imageURL) {
            if (!(options & YYWebImageOptionIgnorePlaceHolder)) {
                self.highlightedImage = placeholder;
            }
            return;
        }
        
        // get the image from memory as quickly as possible
        UIImage *imageFromMemory = nil;
        if (manager.cache &&
            !(options & YYWebImageOptionUseNSURLCache) &&
            !(options & YYWebImageOptionRefreshImageCache)) {
            imageFromMemory = [manager.cache getImageForKey:[manager cacheKeyForURL:imageURL] withType:YYImageCacheTypeMemory];
        }
        if (imageFromMemory) {
            if (!(options & YYWebImageOptionAvoidSetImage)) {
                self.highlightedImage = imageFromMemory;
            }
            if(completion) completion(imageFromMemory, imageURL, YYWebImageFromMemoryCacheFast, YYWebImageStageFinished, nil);
            return;
        }
        
        if (!(options & YYWebImageOptionIgnorePlaceHolder)) {
            self.highlightedImage = placeholder;
        }
        
        __weak typeof(self) _self = self;
        dispatch_async([_YYWebImageSetter setterQueue], ^{
            YYWebImageProgressBlock _progress = nil;
            if (progress) _progress = ^(NSInteger receivedSize, NSInteger expectedSize) {
                dispatch_async(dispatch_get_main_queue(), ^{
                    progress(receivedSize, expectedSize);
                });
            };
            
            __block int32_t newSentinel = 0;
            __block __weak typeof(setter) weakSetter = nil;
            YYWebImageCompletionBlock _completion = ^(UIImage *image, NSURL *url, YYWebImageFromType from, YYWebImageStage stage, NSError *error) {
                __strong typeof(_self) self = _self;
                BOOL setImage = (stage == YYWebImageStageFinished || stage == YYWebImageStageProgress) && image && !(options & YYWebImageOptionAvoidSetImage);
                BOOL showFade = ((options & YYWebImageOptionSetImageWithFadeAnimation) && self.highlighted);
                dispatch_async(dispatch_get_main_queue(), ^{
                    BOOL sentinelChanged = weakSetter && weakSetter.sentinel != newSentinel;
                    if (setImage && self && !sentinelChanged) {
                        if (showFade) {
                            CATransition *transition = [CATransition animation];
                            transition.duration = stage == YYWebImageStageFinished ? _YYWebImageFadeTime : _YYWebImageProgressiveFadeTime;
                            transition.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
                            transition.type = kCATransitionFade;
                            [self.layer addAnimation:transition forKey:_YYWebImageFadeAnimationKey];
                        }
                        self.highlightedImage = image;
                    }
                    if (completion) {
                        if (sentinelChanged) {
                            completion(nil, url, YYWebImageFromNone, YYWebImageStageCancelled, nil);
                        } else {
                            completion(image, url, from, stage, error);
                        }
                    }
                });
            };
            
            newSentinel = [setter setOperationWithSentinel:sentinel url:imageURL options:options manager:manager progress:_progress transform:transform completion:_completion];
            weakSetter = setter;
        });
    });
}

2. - (void)cancelCurrentHighlightedImageRequest;

该方法的作用取消下载高亮图片。

方法实现

- (void)cancelCurrentHighlightedImageRequest {
    _YYWebImageSetter *setter = objc_getAssociatedObject(self, &_YYWebImageHighlightedSetterKey);
    if (setter) [setter cancel];
}

- (int32_t)cancel {
    return [self cancelWithNewURL:nil];
}

- (int32_t)cancelWithNewURL:(NSURL *)imageURL {
    int32_t sentinel;
    dispatch_semaphore_wait(_lock, DISPATCH_TIME_FOREVER);
    if (_operation) {
        [_operation cancel];
        _operation = nil;
    }
    _imageURL = imageURL;
    sentinel = OSAtomicIncrement32(&_sentinel);
    dispatch_semaphore_signal(_lock);
    return sentinel;
}

后记

本篇主要讲述了UIImageView的highlight image部分，感兴趣的可以给个赞或者关注，谢谢~~~