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本篇内容介绍了“ios开发中SDWebImage方法怎么用”的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！源码解析废话不多说看源码。
1:在组件中提供了很多类似这样的方法
- (void)sd_setImageWithURL:(nullable NSURL *)url;- (void)sd_setImageWithURL:(nullable NSURL *)url placeholderImage:(nullable UIImage *)placeholder;2:于是乎所有的方法都会调用下面的这个方法
- (void)sd_internalSetImageWithURL:(nullable NSURL *)url placeholderImage:(nullable UIImage *)placeholder options:(SDWebImageOptions)options operationKey:(nullable NSString *)operationKey setImageBlock:(nullable SDSetImageBlock)setImageBlock progress:(nullable SDWebImageDownloaderProgressBlock)progressBlock completed:(nullable SDExternalCompletionBlock)completedBlock3：下面具体阅读代码 第一行执行的代码
/ SDOperationsDictionary *operationDictionary = [self operationDictionary]; id operations = operationDictionary[key]; if (operations) { if ([operations isKindOfClass:[NSArray class]]) { for (id <SDWebImageOperation> operation in operations) { if (operation) { [operation cancel]; } } } else if ([operations conformsToProtocol:@protocol(SDWebImageOperation)]){ [(id<SDWebImageOperation>) operations cancel]; } [operationDictionary removeObjectForKey:key]; }}字典操作在看一下去字典操作[self operationDictionary]
- (SDOperationsDictionary *)operationDictionary { SDOperationsDictionary *operations = objc_getAssociatedObject(self, &loadOperationKey); // 创建成功返回该字典，直接把该字典当做属性返回 if (operations) { return operations; } operations = [NSMutableDictionary dictionary]; objc_setAssociatedObject(self, &loadOperationKey, operations, OBJC_ASSOCIATION_RETAIN_NONATOMIC); return operations;}看到这里我们在返回继续看 这个函数的代码有点长，耐心看完啊。。。
- (void)sd_internalSetImageWithURL:(nullable NSURL *)url placeholderImage:(nullable UIImage *)placeholder options:(SDWebImageOptions)options operationKey:(nullable NSString *)operationKey setImageBlock:(nullable SDSetImageBlock)setImageBlock progress:(nullable SDWebImageDownloaderProgressBlock)progressBlock completed:(nullable SDExternalCompletionBlock)completedBlock { / [self sd_cancelImageLoadOperationWithKey:validOperationKey]; objc_setAssociatedObject(self, &imageURLKey, url, OBJC_ASSOCIATION_RETAIN_NONATOMIC); if (!(options & SDWebImageDelayPlaceholder)) { dispatch_main_async_safe(^{ [self sd_setImage:placeholder imagedata:nil basedOnClassOrViaCustomSetImageBlock:setImageBlock]; }); } if (url) { // check if activityView is enabled or not if ([self sd_showActivityIndicatorView]) { [self sd_addActivityIndicator]; } __weak __typeof(self)wself = self; id <SDWebImageOperation> operation = [SDWebImageManager.sharedManager loadImageWithURL:url options:options progress:progressBlock completed:^(UIImage *image, NSData *data, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) { __strong __typeof (wself) sself = wself; [sself sd_removeActivityIndicator]; if (!sself) { return; } dispatch_main_async_safe(^{ if (!sself) { return; } if (image && (options & SDWebImageAvoidAutoSetImage) && completedBlock) { completedBlock(image, error, cacheType, url); return; } else if (image) { [sself sd_setImage:image imagedata:data basedOnClassOrViaCustomSetImageBlock:setImageBlock]; [sself sd_setNeedsLayout]; } else { if ((options & SDWebImageDelayPlaceholder)) { [sself sd_setImage:placeholder imagedata:nil basedOnClassOrViaCustomSetImageBlock:setImageBlock]; [sself sd_setNeedsLayout]; } } if (completedBlock && finished) { completedBlock(image, error, cacheType, url); } }); }]; [self sd_setImageLoadOperation:operation forKey:validOperationKey]; } else { dispatch_main_async_safe(^{ [self sd_removeActivityIndicator]; if (completedBlock) { NSError *error = [NSError errorWithDomain:SDWebImageErrorDomain code:-1 userInfo:@{NSLocalizedDescriptionKey : @"Trying to load a nil url"}]; completedBlock(nil, error, SDImageCacheTypeNone, url); } }); }}看一下调用下载函数前的实例化过程这个loadImageWithURL函数在SDWebImageManager，并且是用单列调用,
+ (nonnull instancetype)sharedManager { static dispatch_once_t once; static id instance; dispatch_once(&once, ^{ instance = [self new]; }); return instance;}- (nonnull instancetype)init { SDImageCache *cache = [SDImageCache sharedImageCache]; SDWebImageDownloader *downloader = [SDWebImageDownloader sharedDownloader]; return [self initWithCache:cache downloader:downloader];}- (nonnull instancetype)initWithCache:(nonnull SDImageCache *)cache downloader:(nonnull SDWebImageDownloader *)downloader { if ((self = [super init])) { _imageCache = cache; _imageDownloader = downloader; _failedURLs = [NSMutableSet new]; _runningOperations = [NSMutableArray new]; } return self;}上面都是初始化的操作，然后看下面的函数
- (id <SDWebImageOperation>)loadImageWithURL:(nullable NSURL *)url options:(SDWebImageOptions)options progress:(nullable SDWebImageDownloaderProgressBlock)progressBlock completed:(nullable SDInternalCompletionBlock)completedBlock { // Invoking this method without a completedBlock is pointless NSAssert(completedBlock != nil, @"If you mean to prefetch the image, use -[SDWebImagePrefetcher prefetchURLs] instead"); // Very common mistake is to send the URL using NSString object instead of NSURL. For some strange reason, Xcode won't // throw any warning for this type mismatch. Here we failsafe this error by allowing URLs to be passed as NSString. if ([url isKindOfClass:NSString.class]) { url = [NSURL URLWithString:(NSString *)url]; } // Prevents app crashing on argument type error like sending NSNull instead of NSURL if (![url isKindOfClass:NSURL.class]) { url = nil; } __block SDWebImageCombinedOperation *operation = [SDWebImageCombinedOperation new]; __weak SDWebImageCombinedOperation *weakOperation = operation; BOOL isFailedUrl = NO; if (url) { @synchronized (self.failedURLs) { isFailedUrl = [self.failedURLs containsObject:url]; } } if (url.absoluteString.length == 0 || (!(options & SDWebImageRetryFailed) && isFailedUrl)) { [self callCompletionBlockForOperation:operation completion:completedBlock error:[NSError errorWithDomain:NSURLErrorDomain code:NSURLErrorFileDoesNotExist userInfo:nil] url:url]; return operation; } @synchronized (self.runningOperations) { [self.runningOperations addObject:operation]; } NSString *key = [self cacheKeyForURL:url]; operation.cacheOperation = [self.imageCache queryCacheOperationForKey:key done:^(UIImage *cachedImage, NSData *cachedData, SDImageCacheType cacheType) { if (operation.isCancelled) { [self safelyRemoveOperationFromRunning:operation]; return; } //条件1:在缓存中没有找到图片或者options选项里面包含了SDWebImageRefreshCached(这两项都需要进行请求网络图片的) //条件2:代理允许下载,SDWebImageManagerDelegate的delegate不能响应imageManager:shouldDownloadImageForURL:方法或者能响应方法且方法返回值为YES.也就是没有实现这个方法就是允许的,如果实现了的话,返回YES才是允许 if ((!cachedImage || options & SDWebImageRefreshCached) && (![self.delegate respondsToSelector:@selector(imageManager:shouldDownloadImageForURL:)] || [self.delegate imageManager:self shouldDownloadImageForURL:url])) { //如果在缓存中找到了image且options选项包含SDWebImageRefreshCached,先在主线程完成一次回调,使用的是缓存中找的图片 if (cachedImage && options & SDWebImageRefreshCached) { // If image was found in the cache but SDWebImageRefreshCached is provided, notify about the cached image // AND try to re-download it in order to let a chance to NSURLCache to refresh it from server. [self callCompletionBlockForOperation:weakOperation completion:completedBlock image:cachedImage data:cachedData error:nil cacheType:cacheType finished:YES url:url]; } // 如果没有在缓存中找到image 或者设置了需要请求服务器刷新的选项,则仍需要下载 // download if no image or requested to refresh anyway, and download allowed by delegate SDWebImageDownloaderOptions downloaderOptions = 0; if (options & SDWebImageLowPriority) downloaderOptions |= SDWebImageDownloaderLowPriority; if (options & SDWebImageProgressiveDownload) downloaderOptions |= SDWebImageDownloaderProgressiveDownload; if (options & SDWebImageRefreshCached) downloaderOptions |= SDWebImageDownloaderUseNSURLCache; if (options & SDWebImageContinueInBackground) downloaderOptions |= SDWebImageDownloaderContinueInBackground; if (options & SDWebImageHandlecookies) downloaderOptions |= SDWebImageDownloaderHandlecookies; if (options & SDWebImageAllowInvalidSSLCertificates) downloaderOptions |= SDWebImageDownloaderAllowInvalidSSLCertificates; if (options & SDWebImageHighPriority) downloaderOptions |= SDWebImageDownloaderHighPriority; if (options & SDWebImageScaleDownLargeImages) downloaderOptions |= SDWebImageDownloaderScaleDownLargeImages; if (cachedImage && options & SDWebImageRefreshCached) { // force progressive off if image already cached but forced refreshing // 如果image已经被缓存但是设置了需要请求服务器刷新的选项，强制关闭渐进式选项 downloaderOptions &= ~SDWebImageDownloaderProgressiveDownload; // ignore image read from NSURLCache if image if cached but force refreshing // 如果image已经被缓存但是设置了需要请求服务器刷新的选项，忽略从NSURLCache读取的image downloaderOptions |= SDWebImageDownloaderIgnoreCachedResponse; } SDWebImageDownloadToken *subOperationToken = [self.imageDownloader downloadImageWithURL:url options:downloaderOptions progress:progressBlock completed:^(UIImage *downloadedImage, NSData *downloadedData, NSError *error, BOOL finished) { __strong __typeof(weakOperation) strongOperation = weakOperation; if (!strongOperation || strongOperation.isCancelled) { // Do nothing if the operation was cancelled // 不用做任何事情，如果是取消状态 // See #699 for more details // if we would call the completedBlock, there could be a race condition between this block and another completedBlock for the same object, so if this one is called second, we will overwrite the new data //如果我们调用completedBlock,这个block会和另外一个completedBlock争夺一个对象,因此这个block被调用后会覆盖新的数据 } else if (error) { //进行完成回调 [self callCompletionBlockForOperation:strongOperation completion:completedBlock error:error url:url]; if ( error.code != NSURLErrorNotConnectedToInternet && error.code != NSURLErrorCancelled && error.code != NSURLErrorTimedOut && error.code != NSURLErrorInternationalRoamingOff && error.code != NSURLErrorDataNotAllowed && error.code != NSURLErrorCannotFindHost && error.code != NSURLErrorCannotConnectToHost) { //将失败的url添加到failedURLS的set中去 @synchronized (self.failedURLs) { [self.failedURLs addObject:url]; } } } else { //如果有重试状态,将url从失败列表中移除 if ((options & SDWebImageRetryFailed)) { @synchronized (self.failedURLs) { [self.failedURLs removeObject:url]; } } BOOL cacheOnDisk = !(options & SDWebImageCacheMemoryOnly); //options包含了SDWebImageRefreshCached选项,且缓存中找到了image且没有下载成功 if (options & SDWebImageRefreshCached && cachedImage && !downloadedImage) { // Image refresh hit the NSURLCache cache, do not call the completion block } else if ( //图片下载成功并且 设置了需要变形Image的选项且变形的代理方法已经实现 downloadedImage && (!downloadedImage.images || (options & SDWebImageTransformAnimatedImage)) &&[self.delegate respondsToSelector:@selector(imageManager:transformDownloadedImage:withURL:)] ) { dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{ //调用代理方法完成图片transform UIImage *transformedImage = [self.delegate imageManager:self transformDownloadedImage:downloadedImage withURL:url]; if (transformedImage && finished) { BOOL imageWasTransformed = ![transformedImage isEqual:downloadedImage]; // pass nil if the image was transformed, so we can recalculate the data from the image //对已经transform的图片进行缓存 [self.imageCache storeImage:transformedImage imagedata:(imageWasTransformed ? nil : downloadedData) forKey:key toDisk:cacheOnDisk completion:nil]; } [self callCompletionBlockForOperation:strongOperation completion:completedBlock image:transformedImage data:downloadedData error:nil cacheType:SDImageCacheTypeNone finished:finished url:url]; }); } else { //如果没有图片transform的需求并且图片下载完成且图片存在就直接缓存 if (downloadedImage && finished) { [self.imageCache storeImage:downloadedImage imagedata:downloadedData forKey:key toDisk:cacheOnDisk completion:nil]; } [self callCompletionBlockForOperation:strongOperation completion:completedBlock image:downloadedImage data:downloadedData error:nil cacheType:SDImageCacheTypeNone finished:finished url:url]; } } if (finished) { [self safelyRemoveOperationFromRunning:strongOperation]; } }]; operation.cancelBlock = ^{ [self.imageDownloader cancel:subOperationToken]; __strong __typeof(weakOperation) strongOperation = weakOperation; [self safelyRemoveOperationFromRunning:strongOperation]; }; //在缓存中找到图片(代理不允许下载 或者没有设置SDWebImageRefreshCached选项 满足至少一项) } else if (cachedImage) { __strong __typeof(weakOperation) strongOperation = weakOperation; [self callCompletionBlockForOperation:strongOperation completion:completedBlock image:cachedImage data:cachedData error:nil cacheType:cacheType finished:YES url:url]; [self safelyRemoveOperationFromRunning:operation]; } else { //缓存中没有扎到图片且代理不允许下载 // Image not in cache and download disallowed by delegate __strong __typeof(weakOperation) strongOperation = weakOperation; [self callCompletionBlockForOperation:strongOperation completion:completedBlock image:nil data:nil error:nil cacheType:SDImageCacheTypeNone finished:YES url:url]; [self safelyRemoveOperationFromRunning:operation]; } }]; return operation;}这个函数就进入了SDWebimage缓存的策略了。
先说一下他的这一个策略缓存。
*1：大家都是SDWebiamge都是先从缓存上查找，如果有就直接显示
*2：如果不存在就在沙盒中查找
*2.1如果存在，则把沙盒中的图片添加到imageCache中，取出显示
*2.2 如果不存在在显示占位图，根据URL在operationCache是否存在下载操作
*2.2.1 如果存在，说明该图片正在下载。
*2.2.2如果不存在，创建图片下载操作，放到operationCache中
* 2.3 下载完成，将当前操作队列从operationCache中移除。并将下载的图片的添加在imageCache中。显示
先慢慢体会一下。。。（停留30秒）
开始进入查找函数- (nullable NSOperation *)queryCacheOperationForKey:(nullable NSString *)key done:(nullable SDCacheQueryCompletedBlock)doneBlock { if (!key) { if (doneBlock) { doneBlock(nil, nil, SDImageCacheTypeNone); } return nil; } // 先检查缓存--内存上的数据 // First check the in-memory cache... UIImage *image = [self imageFromMemoryCacheForKey:key]; if (image) { NSData *diskData = nil; if ([image isGIF]) { diskData = [self diskImageDataBySearchingAllPathsForKey:key]; } if (doneBlock) { doneBlock(image, diskData, SDImageCacheTypeMemory); } return nil; } NSOperation *operation = [NSOperation new]; dispatch_async(self.ioQueue, ^{ if (operation.isCancelled) { // do not call the completion if cancelled return; } @autoreleasepool { NSData *diskData = [self diskImageDataBySearchingAllPathsForKey:key]; UIImage *diskImage = [self diskImageForKey:key]; if (diskImage && self.config.shouldCacheImagesInMemory) { NSUInteger cost = SDCacheCostForImage(diskImage); //self.memCache是NSCache创建的一个对象 [self.memCache setObject:diskImage forKey:key cost:cost]; } if (doneBlock) { dispatch_async(dispatch_get_main_queue(), ^{ doneBlock(diskImage, diskData, SDImageCacheTypeDisk); }); } } }); return operation;}快速查找缓存的方法回调看完该函数以后在回到上面的看这个快速查找缓存的方法回调
operation.cacheOperation = [self.imageCache queryDiskCacheForKey:key done:^(UIImage *image, SDImageCacheType cacheType) { if (operation.isCancelled) { @synchronized (self.runningOperations) { [self.runningOperations removeObject:operation]; } return; } if ((!image || options & SDWebImageRefreshCached) && (![self.delegate respondsToSelector:@selector(imageManager:shouldDownloadImageForURL:)] || [self.delegate imageManager:self shouldDownloadImageForURL:url])) {//如果在缓存中找到了image且options选项包含SDWebImageRefreshCached,先在主线程完成一次回调,使用的是缓存中找的图片 if (image && options & SDWebImageRefreshCached) { dispatch_main_sync_safe(^{ // 如果在缓存中找到了image但是设置了SDWebImageRefreshCached选项，传递缓存的image，同时尝试重新下载它来让NSURLCache有机会接收服务器端的更新 completedBlock(image, nil, cacheType, YES, url); }); } // 如果没有在缓存中找到image 或者设置了需要请求服务器刷新的选项,则仍需要下载 SDWebImageDownloaderOptions downloaderOptions = 0; //开始各种options的判断 if (options & SDWebImageLowPriority) downloaderOptions |= SDWebImageDownloaderLowPriority; if (options & SDWebImageProgressiveDownload) downloaderOptions |= SDWebImageDownloaderProgressiveDownload; if (options & SDWebImageRefreshCached) downloaderOptions |= SDWebImageDownloaderUseNSURLCache; if (options & SDWebImageContinueInBackground) downloaderOptions |= SDWebImageDownloaderContinueInBackground; if (options & SDWebImageHandlecookies) downloaderOptions |= SDWebImageDownloaderHandlecookies; if (options & SDWebImageAllowInvalidSSLCertificates) downloaderOptions |= SDWebImageDownloaderAllowInvalidSSLCertificates; if (options & SDWebImageHighPriority) downloaderOptions |= SDWebImageDownloaderHighPriority; if (image && options & SDWebImageRefreshCached) { // 如果image已经被缓存但是设置了需要请求服务器刷新的选项，强制关闭渐进式选项 downloaderOptions &= ~SDWebImageDownloaderProgressiveDownload; // 如果image已经被缓存但是设置了需要请求服务器刷新的选项，忽略从NSURLCache读取的image downloaderOptions |= SDWebImageDownloaderIgnoreCachedResponse; } //创建下载操作,先使用self.imageDownloader下载 id <SDWebImageOperation> subOperation = [self.imageDownloader downloadImageWithURL:url options:downloaderOptions progress:progressBlock completed:^(UIImage *downloadedImage, NSData *data, NSError *error, BOOL finished) { __strong __typeof(weakOperation) strongOperation = weakOperation; if (!strongOperation || strongOperation.isCancelled) { // Do nothing if the operation was cancelled //如果操作取消了,不做任何事情 // if we would call the completedBlock, there could be a race condition between this block and another completedBlock for the same object, so if this one is called second, we will overwrite the new data //如果我们调用completedBlock,这个block会和另外一个completedBlock争夺一个对象,因此这个block被调用后会覆盖新的数据 } else if (error) { //进行完成回调 dispatch_main_sync_safe(^{ if (strongOperation && !strongOperation.isCancelled) { completedBlock(nil, error, SDImageCacheTypeNone, finished, url); } }); //将url添加到失败列表里面 if ( error.code != NSURLErrorNotConnectedToInternet && error.code != NSURLErrorCancelled && error.code != NSURLErrorTimedOut && error.code != NSURLErrorInternationalRoamingOff && error.code != NSURLErrorDataNotAllowed && error.code != NSURLErrorCannotFindHost && error.code != NSURLErrorCannotConnectToHost) { @synchronized (self.failedURLs) { [self.failedURLs addObject:url]; } } } else { //如果设置了下载失败重试,将url从失败列表中去掉 if ((options & SDWebImageRetryFailed)) { @synchronized (self.failedURLs) { [self.failedURLs removeObject:url]; } } BOOL cacheOnDisk = !(options & SDWebImageCacheMemoryOnly); //options包含了SDWebImageRefreshCached选项,且缓存中找到了image且没有下载成功 if (options & SDWebImageRefreshCached && image && !downloadedImage) { // Image refresh hit the NSURLCache cache, do not call the completion block // 图片刷新遇到了NSSURLCache中有缓存的状况，不调用完成回调。 } //图片下载成功并且 设置了需要变形Image的选项且变形的代理方法已经实现 else if (downloadedImage && (!downloadedImage.images || (options & SDWebImageTransformAnimatedImage)) && [self.delegate respondsToSelector:@selector(imageManager:transformDownloadedImage:withURL:)]) {//全局队列异步执行 dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{ //调用代理方法完成图片transform UIImage *transformedImage = [self.delegate imageManager:self transformDownloadedImage:downloadedImage withURL:url]; if (transformedImage && finished) { BOOL imageWasTransformed = ![transformedImage isEqual:downloadedImage]; //对已经transform的图片进行缓存 [self.imageCache storeImage:transformedImage recalculateFromImage:imageWasTransformed imagedata:(imageWasTransformed ? nil : data) forKey:key toDisk:cacheOnDisk]; } //主线程执行完成回调 dispatch_main_sync_safe(^{ if (strongOperation && !strongOperation.isCancelled) { completedBlock(transformedImage, nil, SDImageCacheTypeNone, finished, url); } }); }); }//如果没有图片transform的需求并且图片下载完成且图片存在就直接缓存 else { if (downloadedImage && finished) { [self.imageCache storeImage:downloadedImage recalculateFromImage:NO imagedata:data forKey:key toDisk:cacheOnDisk]; } //主线程完成回调 dispatch_main_sync_safe(^{ if (strongOperation && !strongOperation.isCancelled) { completedBlock(downloadedImage, nil, SDImageCacheTypeNone, finished, url); } }); } } if (finished) { // 从正在进行的操作列表中移除这组合操作 @synchronized (self.runningOperations) { if (strongOperation) { [self.runningOperations removeObject:strongOperation]; } } } }]; //设置组合操作取消得得回调 operation.cancelBlock = ^{ [subOperation cancel]; @synchronized (self.runningOperations) { __strong __typeof(weakOperation) strongOperation = weakOperation; if (strongOperation) { [self.runningOperations removeObject:strongOperation]; } } }; }//处理其他情况//case1.在缓存中找到图片(代理不允许下载 或者没有设置SDWebImageRefreshCached选项 满足至少一项) else if (image) { //完成回调 dispatch_main_sync_safe(^{ __strong __typeof(weakOperation) strongOperation = weakOperation; if (strongOperation && !strongOperation.isCancelled) { completedBlock(image, nil, cacheType, YES, url); } }); //从正在进行的操作列表中移除组合操作 @synchronized (self.runningOperations) { [self.runningOperations removeObject:operation]; } } //case2:缓存中没有扎到图片且代理不允许下载 else { //主线程执行完成回调 dispatch_main_sync_safe(^{ __strong __typeof(weakOperation) strongOperation = weakOperation; if (strongOperation && !weakOperation.isCancelled) { completedBlock(nil, nil, SDImageCacheTypeNone, YES, url); } }); //从正在执行的操作列表中移除组合操作 @synchronized (self.runningOperations) { [self.runningOperations removeObject:operation]; } } }];总结一下函数调用1.先调用- (void)sd_setImageWithURL:(nullable NSURL *)url placeholderImage:(nullable UIImage *)placeholder;2.设置图片- (void)sd_internalSetImageWithURL:(nullable NSURL *)url placeholderImage:(nullable UIImage *)placeholder options:(SDWebImageOptions)options operationKey:(nullable NSString *)operationKey setImageBlock:(nullable SDSetImageBlock)setImageBlock progress:(nullable SDWebImageDownloaderProgressBlock)progressBlock completed:(nullable SDExternalCompletionBlock)completedBlock2.1 取消该控件对应的之前的所有的下载操作
- (void)sd_cancelImageLoadOperationWithKey:(nullable NSString *)key;2.2 开始根据图片的url做为key去查找
- (id <SDWebImageOperation>)loadImageWithURL:(nullable NSURL *)url options:(SDWebImageOptions)options progress:(nullable SDWebImageDownloaderProgressBlock)progressBlock completed:(nullable SDInternalCompletionBlock)completedBlock2.2.1 查找内存和硬盘上的缓存
- (nullable NSOperation *)queryCacheOperationForKey:(nullable NSString *)key done:(nullable SDCacheQueryCompletedBlock)doneBlock;2.3 创建下载队列下载图片
- (nullable SDWebImageDownloadToken *)downloadImageWithURL:(nullable NSURL *)url options:(SDWebImageDownloaderOptions)options progress:(nullable SDWebImageDownloaderProgressBlock)progressBlock completed:(nullable SDWebImageDownloaderCompletedBlock)completedBlock;2.4 最后将进行的操作，放到view对应的opationsDicaionary的字典中。记录当前的操作队列
- (void)sd_setImageLoadOperation:(nullable id)operation forKey:(nullable NSString *)key“ios开发中SDWebImage方法怎么用”的内容就介绍到这里了，感谢大家的阅读。如果想了解更多行业相关的知识可以关注花开半夏网站，小编将为大家输出更多高质量的实用文章！
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