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SDWebImage解读解读

文章目录文章目录类方法协议分类解析SDWebImageOperation NSOperation的分类UIImageView+WebCache UIImageView分类

UIView+WebCache UIView分类UIView+WebCacheOperation UIView分类SDWebImageCombinedOperation 继承自

NSObjectSDWebImageManagerSDWebImageManagerDelegateSDImageCache 协议SDImageLoader 协议

SDWebImageDownloader 下载类，此分类遵循SDImageLoader协议SDWebImageDownloadToken 每一个下载的关联对象，

可以取消下载操作遵循SDWebImageOperation协议SDWebImageDownloaderOperation 下载工具类

SDImageCachesManager 缓存管理类遵循 SDImageCache 协议SDImageCache 维护内存缓存和磁盘缓存SDMemoryCache

内存缓存类继承NSCacheSDDiskCache 磁盘缓存类继承NSObject总结

此部分会省略一些代码，请知晓 SD下载地址

类类方法方法协议协议分类解析分类解析

SDWebImageOperation NSOperation的分类的分类

是NSOperation分类遵循SDWebImageOperation 协议

@protocol SDWebImageOperation

- (void)cancel;

@end

@interface NSOperation (SDWebImageOperation)

@end

UIImageView+WebCache UIImageView分类分类

// 采用SDWebImage对UIImageView的对象加载图片的方法都会调用此方法

- (void)sd_setImageWithURL:(nullable NSURL *)url

placeholderImage:(nullable UIImage *)placeholder

options:(SDWebImageOptions)options

context:(nullable SDWebImageContext *)context

progress:(nullable SDImageLoaderProgressBlock)progressBlock

completed:(nullable SDExternalCompletionBlock)completedBlock {

// UIView+WebCache 内部方法

[self sd_internalSetImageWithURL:url

placeholderImage:placeholder

options:options

context:context

setImageBlock:nil

progress:progressBlock

completed:^(UIImage * _Nullable image, NSData * _Nullable data, NSError * _Nullable error, SDImageCacheType cacheType, BOOL finished, NSURL *

_Nullable imageURL) {

if (completedBlock) {

completedBlock(image, error, cacheType, imageURL);

}

}];

UIView+WebCache UIView分类分类

因为此方法需要在需要在 UIButton 和 UIImageView 上重用所以添加到它们的根类上

- (void)sd_internalSetImageWithURL:(nullable NSURL *)url

placeholderImage:(nullable UIImage *)placeholder

options:(SDWebImageOptions)options

context:(nullable SDWebImageContext *)context

setImageBlock:(nullable SDSetImageBlock)setImageBlock

progress:(nullable SDImageLoaderProgressBlock)progressBlock

completed:(nullable SDInternalCompletionBlock)completedBlock {

context = [context copy]; // copy to avoid mutable object

NSString *validOperationKey = context[SDWebImageContextSetImageOperationKey];

// SDOperationsDictionary对象中取出当前key对应的对象并取消所有操作不会影响之后进行的下载操作

[self sd_cancelImageLoadOperationWithKey:validOperationKey];

if (!(options & SDWebImageDelayPlaceholder)) {

dispatch_main_async_safe(^{

[self sd_setImage:placeholder imageData:nil basedOnClassOrViaCustomSetImageBlock:setImageBlock cacheType:SDImageCacheTypeNone

imageURL:url];

});

}

if (url) {

SDWebImageManager *manager = context[SDWebImageContextCustomManager];

if (!manager) {

manager = [SDWebImageManager sharedManager];

}

SDImageLoaderProgressBlock combinedProgressBlock = ^(NSInteger receivedSize, NSInteger expectedSize, NSURL * _Nullable targetURL) {

if (imageProgress) {

imageProgress.totalUnitCount = expectedSize;

imageProgress.completedUnitCount = receivedSize;

}

if (progressBlock) {

progressBlock(receivedSize, expectedSize, targetURL);

}

};

@weakify(self);

// 请看SDWebImageManager部分返回遵循SDWebImageOperation协议的对象！！！

id operation = [manager loadImageWithURL:url options:options context:context progress:combinedProgressBlock completed:^(UIImage *image, NSData

*data, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {

@strongify(self);

if (!self) { return; }

// if the progress not been updated, mark it to complete state

if (imageProgress && finished && !error && imageProgress.totalUnitCount == 0 && imageProgress.completedUnitCount == 0) {

imageProgress.totalUnitCount = SDWebImageProgressUnitCountUnknown;

imageProgress.completedUnitCount = SDWebImageProgressUnitCountUnknown;

}

BOOL shouldCallCompletedBlock = finished || (options & SDWebImageAvoidAutoSetImage);

BOOL shouldNotSetImage = ((image && (options & SDWebImageAvoidAutoSetImage)) ||

(!image && !(options & SDWebImageDelayPlaceholder)));

SDWebImageNoParamsBlock callCompletedBlockClojure = ^{

if (!self) { return; }

if (!shouldNotSetImage) { // 刷新UI

[self sd_setNeedsLayout];

}

if (completedBlock && shouldCallCompletedBlock) {

completedBlock(image, data, error, cacheType, finished, url);

}

};

if (shouldNotSetImage) {

dispatch_main_async_safe(callCompletedBlockClojure);

return;

}

UIImage *targetImage = nil;

NSData *targetData = nil;

if (image) {

// case 2a: we got an image and the SDWebImageAvoidAutoSetImage is not set

targetImage = image;

targetData = data;

} else if (options & SDWebImageDelayPlaceholder) {

// case 2b: we got no image and the SDWebImageDelayPlaceholder flag is set

targetImage = placeholder;

targetData = nil;

}

// 设置图片

dispatch_main_async_safe(^{

[self sd_setImage:targetImage imageData:targetData basedOnClassOrViaCustomSetImageBlock:setImageBlock transition:transition

cacheType:cacheType imageURL:imageURL];

//#endif

callCompletedBlockClojure();

});

}];

// 添加到 SDOperationsDictionary 对象中添加一个键值对, 来表示操作的正在进行，它将 opertion 存储到 SDOperationsDictionary 中方便以后的 cancel.

[self sd_setImageLoadOperation:operation forKey:validOperationKey];

} else { // 错误处理}

}

- (void)sd_cancelImageLoadOperationWithKey:(nullable NSString *)key {

if (key) {

// Cancel in progress downloader from queue

SDOperationsDictionary *operationDictionary = [self sd_operationDictionary];

id operation;

@synchronized (self) {

operation = [operationDictionary objectForKey:key];

}

if (operation) {

if ([operation conformsToProtocol:@protocol(SDWebImageOperation)]) {

[operation cancel]; // 取消操作

}

@synchronized (self) {

[operationDictionary removeObjectForKey:key];

}

UIView+WebCacheOperation UIView分类分类

typedef NSMapTable<NSString *, id> SDOperationsDictionary; // 通过这种数据结构，存储操作

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