/* * This file is part of the SDWebImage package. * (c) Olivier Poitrey * * For the full copyright and license information, please view the LICENSE * file that was distributed with this source code. */#import "SDWebImageCompat.h"#import "SDWebImageOperation.h"#import "SDWebImageDownloader.h"#import "SDImageCache.h"typedef NS_OPTIONS(NSUInteger, SDWebImageOptions) { /** * By default, when a URL fail to be downloaded, the URL is blacklisted so the library won't keep trying. * This flag disable this blacklisting. */ /** *默认情况下,如果一个url在下载的时候失败了,那么这个url会被加入黑名单并且library不会尝试再次下载,这个flag会阻止library把失败的url加入黑名单(简单来说如果选择了这个flag,那么即使某个url下载失败了,sdwebimage还是会尝试再次下载他.) */ SDWebImageRetryFailed = 1 << 0, /** * By default, image downloads are started during UI interactions, this flags disable this feature, * leading to delayed download on UIScrollView deceleration for instance. */ /** *默认情况下,图片会在交互发生的时候下载(例如你滑动tableview的时候),这个flag会禁止这个特性,导致的结果就是在scrollview减速的时候 *才会开始下载(也就是你滑动的时候scrollview不下载,你手从屏幕上移走,scrollview开始减速的时候才会开始下载图片) */ SDWebImageLowPriority = 1 << 1, /** * This flag disables on-disk caching */ /* *这个flag禁止磁盘缓存,只有内存缓存 */ SDWebImageCacheMemoryOnly = 1 << 2, /** * This flag enables progressive download, the image is displayed progressively during download as a browser would do. * By default, the image is only displayed once completely downloaded. */ /* *这个flag会在图片下载的时候就显示(就像你用浏览器浏览网页的时候那种图片下载,一截一截的显示(待确认)) * */ SDWebImageProgressiveDownload = 1 << 3, /** * Even if the image is cached, respect the HTTP response cache control, and refresh the image from remote location if needed. * The disk caching will be handled by NSURLCache instead of SDWebImage leading to slight performance degradation. * This option helps deal with images changing behind the same request URL, e.g. Facebook graph api profile pics. * If a cached image is refreshed, the completion block is called once with the cached image and again with the final image. * * Use this flag only if you can't make your URLs static with embeded cache busting parameter. */ /* *这个选项的意思看的不是很懂,大意是即使一个图片缓存了,还是会重新请求.并且缓存侧略依据NSURLCache而不是SDWebImage. * */ SDWebImageRefreshCached = 1 << 4, /** * In iOS 4+, continue the download of the image if the app goes to background. This is achieved by asking the system for * extra time in background to let the request finish. If the background task expires the operation will be cancelled. */ /* *启动后台下载,加入你进入一个页面,有一张图片正在下载这时候你让app进入后台,图片还是会继续下载(这个估计要开backgroundfetch才有用) */ SDWebImageContinueInBackground = 1 << 5, /** * Handles cookies stored in NSHTTPCookieStore by setting * NSMutableURLRequest.HTTPShouldHandleCookies = YES; */ /* *可以控制存在NSHTTPCookieStore的cookies.(我没用过,等用过的人过来解释一下) */ SDWebImageHandleCookies = 1 << 6, /** * Enable to allow untrusted SSL ceriticates. * Useful for testing purposes. Use with caution in production. */ /* *允许不安全的SSL证书,在正式环境中慎用 */ SDWebImageAllowInvalidSSLCertificates = 1 << 7, /** * By default, image are loaded in the order they were queued. This flag move them to * the front of the queue and is loaded immediately instead of waiting for the current queue to be loaded (which * could take a while). */ /* *默认情况下,image在装载的时候是按照他们在队列中的顺序装载的(就是先进先出).这个flag会把他们移动到队列的前端,并且立刻装载 *而不是等到当前队列装载的时候再装载. */ SDWebImageHighPriority = 1 << 8, /** * By default, placeholder images are loaded while the image is loading. This flag will delay the loading * of the placeholder image until after the image has finished loading. */ /* *默认情况下,占位图会在图片下载的时候显示.这个flag开启会延迟占位图显示的时间,等到图片下载完成之后才会显示占位图.(等图片显示完了我干嘛还显示占位图?或许是我理解错了?) */ SDWebImageDelayPlaceholder = 1 << 9, /** * We usually don't call transformDownloadedImage delegate method on animated images, * as most transformation code would mangle it. * Use this flag to transform them anyway. */ /* *是否transform图片(没用过,还要再看,但是据我估计,是否是图片有可能方向不对需要调整方向,例如采用iPhone拍摄的照片如果不纠正方向,那么图片是向左旋转90度的.可能很多人不知道iPhone的摄像头并不是竖直的,而是向左偏了90度.具体请google.) */ SDWebImageTransformAnimatedImage = 1 << 10,};typedef void(^SDWebImageCompletionBlock)(UIImage *image, NSError *error, SDImageCacheType cacheType, NSURL *imageURL);typedef void(^SDWebImageCompletionWithFinishedBlock)(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL);typedef NSString *(^SDWebImageCacheKeyFilterBlock)(NSURL *url);@class SDWebImageManager;@protocol SDWebImageManagerDelegate @optional/** * Controls which image should be downloaded when the image is not found in the cache. * * @param imageManager The current `SDWebImageManager` * @param imageURL The url of the image to be downloaded * * @return Return NO to prevent the downloading of the image on cache misses. If not implemented, YES is implied. *//* *主要作用是当缓存里没有发现某张图片的缓存时,是否选择下载这张图片(默认是yes),可以选择no,那么sdwebimage在缓存中没有找到这张图片的时候不会选择下载 */- (BOOL)imageManager:(SDWebImageManager *)imageManager shouldDownloadImageForURL:(NSURL *)imageURL;/** * Allows to transform the image immediately after it has been downloaded and just before to cache it on disk and memory. * NOTE: This method is called from a global queue in order to not to block the main thread. * * @param imageManager The current `SDWebImageManager` * @param image The image to transform * @param imageURL The url of the image to transform * * @return The transformed image object. *//** *在图片下载完成并且还没有加入磁盘缓存或者内存缓存的时候就transform这个图片.这个方法是在异步线程执行的,防治阻塞主线程. *至于为什么在异步执行很简单,对一张图片纠正方向(也就是transform)是很耗资源的,一张2M大小的图片纠正方向你可以用instrument测试一下耗时. *很恐怖 */- (UIImage *)imageManager:(SDWebImageManager *)imageManager transformDownloadedImage:(UIImage *)image withURL:(NSURL *)imageURL;@end/** * The SDWebImageManager is the class behind the UIImageView+WebCache category and likes. * It ties the asynchronous downloader (SDWebImageDownloader) with the image cache store (SDImageCache). * You can use this class directly to benefit from web image downloading with caching in another context than * a UIView. * * Here is a simple example of how to use SDWebImageManager: * * @codeSDWebImageManager *manager = [SDWebImageManager sharedManager];[manager downloadImageWithURL:imageURL options:0 progress:nil completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) { if (image) { // do something with image } }]; * @endcode *//* *这一段是阐述SDWebImageManager是干嘛的.其实UIImageView+WebCache这个category背后执行操作的就是这个SDWebImageManager.他会绑定一个下载器也就是SDWebImageDownloader和一个缓存SDImageCache.后面的大意应该是讲你可以直接使用一个其他上下文环境的SDWebImageManager,而不是仅仅限于一个UIView. */@interface SDWebImageManager : NSObject@property (weak, nonatomic) id delegate;/** *如同上文所说,一个SDWebImageManager会绑定一个imageCache和一个下载器. */@property (strong, nonatomic, readonly) SDImageCache *imageCache;@property (strong, nonatomic, readonly) SDWebImageDownloader *imageDownloader;/** * The cache filter is a block used each time SDWebImageManager need to convert an URL into a cache key. This can * be used to remove dynamic part of an image URL. * * The following example sets a filter in the application delegate that will remove any query-string from the * URL before to use it as a cache key: * * @code[[SDWebImageManager sharedManager] setCacheKeyFilter:^(NSURL *url) { url = [[NSURL alloc] initWithScheme:url.scheme host:url.host path:url.path]; return [url absoluteString];}]; * @endcode *//* * 这个cacheKeyFilter是干嘛的呢?很简单.1他是一个block.2.这个block的作用就是生成一个image的key.因为sdwebimage的缓存原理你可以当成是一个字典,每一个字典的value就是一张image,那么这个value对应的key是什么呢?就是cacheKeyFilter根据某个规则对这个图片的url做一些操作生成的.上面的示例就显示了怎么利用这个block把image的url重新组合生成一个key.以后当sdwebimage检测到你 */@property (nonatomic, copy) SDWebImageCacheKeyFilterBlock cacheKeyFilter;/** * Returns global SDWebImageManager instance. * * @return SDWebImageManager shared instance *//* *这个不用我解释了吧,生成一个SDWebImagemanager的单例. */+ (SDWebImageManager *)sharedManager;/** * Downloads the image at the given URL if not present in cache or return the cached version otherwise. * 从给定的URL中下载一个之前没有被缓存的Image. * * @param url The URL to the image * @param options A mask to specify options to use for this request * @param progressBlock A block called while image is downloading * @param completedBlock A block called when operation has been completed. * * This parameter is required. * * This block has no return value and takes the requested UIImage as first parameter. * In case of error the image parameter is nil and the second parameter may contain an NSError. * * The third parameter is an `SDImageCacheType` enum indicating if the image was retrived from the local cache * or from the memory cache or from the network. * * The last parameter is set to NO when the SDWebImageProgressiveDownload option is used and the image is * downloading. This block is thus called repetidly with a partial image. When image is fully downloaded, the * block is called a last time with the full image and the last parameter set to YES. * * @return Returns an NSObject conforming to SDWebImageOperation. Should be an instance of SDWebImageDownloaderOperation *//* * 这个方法主要就是SDWebImage下载图片的方法了. * 第一个参数是必须要的,就是image的url * 第二个参数就是我们上面的Options,你可以定制化各种各样的操作.详情参上. * 第三个参数是一个回调block,用于图片在下载过程中的回调.(英文注释应该是有问题的.) * 第四个参数是一个下载完成的回调.会在图片下载完成后回调. * 返回值是一个NSObject类,并且这个NSObject类是conforming一个协议这个协议叫做SDWebImageOperation,这个协议很简单,就是一个cancel掉operation的协议. */- (id )downloadImageWithURL:(NSURL *)url options:(SDWebImageOptions)options progress:(SDWebImageDownloaderProgressBlock)progressBlock completed:(SDWebImageCompletionWithFinishedBlock)completedBlock;/** * Saves image to cache for given URL * * @param image The image to cache * @param url The URL to the image * *//* * 将图片存入cache的方法,类似于字典的setValue: forKey: */- (void)saveImageToCache:(UIImage *)image forURL:(NSURL *)url;/** * Cancel all current opreations *//* *取消掉当前所有的下载图片的operation */- (void)cancelAll;/** * Check one or more operations running *//* * check一下是否有一个或者多个operation正在执行(简单来说就是check是否有图片在下载) */- (BOOL)isRunning;/** * Check if image has already been cached * * @param url image url * * @return if the image was already cached *//* * 通过一个image的url是否已经存在,如果存在返回yes,否则返回no */- (BOOL)cachedImageExistsForURL:(NSURL *)url;/** * Check if image has already been cached on disk only * * @param url image url * * @return if the image was already cached (disk only) *//* * 检测一个image是否已经被缓存到磁盘(是否存且仅存在disk里). */- (BOOL)diskImageExistsForURL:(NSURL *)url;/** * Async check if image has already been cached * * @param url image url * @param completionBlock the block to be executed when the check is finished * * @note the completion block is always executed on the main queue *//* * 如果检测到图片已经被缓存,那么执行回调block.这个block会永远执行在主线程.也就是你可以在这个回调block里更新ui. */- (void)cachedImageExistsForURL:(NSURL *)url completion:(SDWebImageCheckCacheCompletionBlock)completionBlock;/** * Async check if image has already been cached on disk only * * @param url image url * @param completionBlock the block to be executed when the check is finished * * @note the completion block is always executed on the main queue *//* * 如果检测到图片已经被缓存在磁盘(存且仅存在disk),那么执行回调block.这个block会永远执行在主线程.也就是你可以在这个回调block里更新ui. */- (void)diskImageExistsForURL:(NSURL *)url completion:(SDWebImageCheckCacheCompletionBlock)completionBlock;/** *Return the cache key for a given URL *//* * 通过image的url返回image存在缓存里的key.有人会问了,为什么不直接把图片的url当做image的key来使用呢?而是非要对url做一些处理才能当做key.我的解释是,我也不太清楚.可能为了防止重复吧. */- (NSString *)cacheKeyForURL:(NSURL *)url;@end#pragma mark - Deprecatedtypedef void(^SDWebImageCompletedBlock)(UIImage *image, NSError *error, SDImageCacheType cacheType) __deprecated_msg("Block type deprecated. Use `SDWebImageCompletionBlock`");typedef void(^SDWebImageCompletedWithFinishedBlock)(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished) __deprecated_msg("Block type deprecated. Use `SDWebImageCompletionWithFinishedBlock`");// 已被废弃@interface SDWebImageManager (Deprecated)/** * Downloads the image at the given URL if not present in cache or return the cached version otherwise. * * @deprecated This method has been deprecated. Use `downloadImageWithURL:options:progress:completed:` */- (id )downloadWithURL:(NSURL *)url options:(SDWebImageOptions)options progress:(SDWebImageDownloaderProgressBlock)progressBlock completed:(SDWebImageCompletedWithFinishedBlock)completedBlock __deprecated_msg("Method deprecated. Use `downloadImageWithURL:options:progress:completed:`");@end/* * This file is part of the SDWebImage package. * (c) Olivier Poitrey * * For the full copyright and license information, please view the LICENSE * file that was distributed with this source code. */#import "SDWebImageManager.h"#import // 内部类.@interface SDWebImageCombinedOperation : NSObject @property (assign, nonatomic, getter = isCancelled) BOOL cancelled;@property (copy, nonatomic) SDWebImageNoParamsBlock cancelBlock;@property (strong, nonatomic) NSOperation *cacheOperation;@end@interface SDWebImageManager ()@property (strong, nonatomic, readwrite) SDImageCache *imageCache;@property (strong, nonatomic, readwrite) SDWebImageDownloader *imageDownloader;@property (strong, nonatomic) NSMutableSet *failedURLs;@property (strong, nonatomic) NSMutableArray *runningOperations;@end@implementation SDWebImageManager// 利用disptach_once 特性生成一个单例,用烂了的方法.不赘述.+ (id)sharedManager { static dispatch_once_t once; static id instance; dispatch_once(&once, ^{ instance = [self new]; }); return instance;}// 初始化方法.// 1.获得一个SDImageCache的单例.2.获取一个SDWebImageDownloader的单例.3.新建一个MutableSet来存储下载失败的url.// 4.新建一个用来存储下载operation的可变数组.// 为什么不用MutableArray储存下载失败的URL?// 因为NSSet类有一个特性,就是Hash.实际上NSSet是一个哈希表,哈希表比数组优秀的地方是什么呢?就是查找速度快.查找同样一个元素,哈希表只需要通过key// 即可取到,而数组至少需要遍历依次.因为SDWebImage里有关失败URL的业务需求是,一个失败的URL只需要储存一次.这样的话Set自然比Array更合适.- (id)init { if ((self = [super init])) { _imageCache = [self createCache]; _imageDownloader = [SDWebImageDownloader sharedDownloader]; _failedURLs = [NSMutableSet new]; _runningOperations = [NSMutableArray new]; } return self;}// 获取一个cache的单例- (SDImageCache *)createCache { return [SDImageCache sharedImageCache];}// 利用Image的URL生成一个缓存时需要的key.// 这里有两种情况,第一种是如果检测到cacheKeyFilter不为空时,利用cacheKeyFilter来处理URL生成一个key.// 如果为空,那么直接返回URL的string内容,当做key.- (NSString *)cacheKeyForURL:(NSURL *)url { if (self.cacheKeyFilter) { return self.cacheKeyFilter(url); } else { return [url absoluteString]; }}// 检测一张图片是否已被缓存.// 首先检测内存缓存是否存在这张图片,如果已有,直接返回yes.// 如果内存缓存里没有这张图片,那么调用diskImageExistsWithKey这个方法去硬盘缓存里找- (BOOL)cachedImageExistsForURL:(NSURL *)url { NSString *key = [self cacheKeyForURL:url]; if ([self.imageCache imageFromMemoryCacheForKey:key] != nil) return YES; return [self.imageCache diskImageExistsWithKey:key];}// 检测硬盘里是否缓存了图片- (BOOL)diskImageExistsForURL:(NSURL *)url { NSString *key = [self cacheKeyForURL:url]; return [self.imageCache diskImageExistsWithKey:key];}// 首先生成一个用来cache 住Image的key(利用key的url生成)// 然后检测内存缓存里是否已经有这张图片// 如果已经被缓存,那么再主线程里回调block// 如果没有检测到,那么调用diskImageExistsWithKey,这个方法会在异步线程里,将图片存到硬盘,当然在存图之前也会检测是否已在硬盘缓存图片.- (void)cachedImageExistsForURL:(NSURL *)url completion:(SDWebImageCheckCacheCompletionBlock)completionBlock { NSString *key = [self cacheKeyForURL:url]; BOOL isInMemoryCache = ([self.imageCache imageFromMemoryCacheForKey:key] != nil); if (isInMemoryCache) { // making sure we call the completion block on the main queue dispatch_async(dispatch_get_main_queue(), ^{ if (completionBlock) { completionBlock(YES); } }); return; } [self.imageCache diskImageExistsWithKey:key completion:^(BOOL isInDiskCache) { // the completion block of checkDiskCacheForImageWithKey:completion: is always called on the main queue, no need to further dispatch if (completionBlock) { completionBlock(isInDiskCache); } }];}//将图片存入硬盘- (void)diskImageExistsForURL:(NSURL *)url completion:(SDWebImageCheckCacheCompletionBlock)completionBlock { NSString *key = [self cacheKeyForURL:url]; [self.imageCache diskImageExistsWithKey:key completion:^(BOOL isInDiskCache) { // the completion block of checkDiskCacheForImageWithKey:completion: is always called on the main queue, no need to further dispatch if (completionBlock) { completionBlock(isInDiskCache); } }];}// 通过url建立一个operation用来下载图片.- (id )downloadImageWithURL:(NSURL *)url options:(SDWebImageOptions)options progress:(SDWebImageDownloaderProgressBlock)progressBlock completed:(SDWebImageCompletionWithFinishedBlock)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; // 创建一个互斥锁防止现在有别的线程修改failedURLs. // 判断这个url是否是fail过的.如果url failed过的那么isFailedUrl就是true @synchronized (self.failedURLs) { isFailedUrl = [self.failedURLs containsObject:url]; } // 如果url不存在那么直接返回一个block,如果url存在.那么继续进行判断. // options与SDWebImageRetryFailed这个option进行按位与操作.判断用户的options里是否有retry这个option. // 如果用户的options里没有retry这个选项并且isFaileUrl 是true.那么就回调一个error的block. if (!url || (!(options & SDWebImageRetryFailed) && isFailedUrl)) { dispatch_main_sync_safe(^{ NSError *error = [NSError errorWithDomain:NSURLErrorDomain code:NSURLErrorFileDoesNotExist userInfo:nil]; completedBlock(nil, error, SDImageCacheTypeNone, YES, url); }); return operation; } // 创建一个互斥锁防止现在有别的线程修改runningOperations. @synchronized (self.runningOperations) { [self.runningOperations addObject:operation]; } NSString *key = [self cacheKeyForURL:url]; // cacheOperation应该是一个用来下载图片并且缓存的operation operation.cacheOperation = [self.imageCache queryDiskCacheForKey:key done:^(UIImage *image, SDImageCacheType cacheType) { // 判断operation这时候有没有执行cancel操作,如果cancel掉了就把这个operation从我们的operation数组里remove掉然后return 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])) { if (image && options & SDWebImageRefreshCached) { dispatch_main_sync_safe(^{ // If image was found in the cache bug 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. completedBlock(image, nil, cacheType, YES, url); }); } // download if no image or requested to refresh anyway, and download allowed by delegate // 下面都是判断我们的options里包含哪些SDWebImageOptions,然后给我们的downloaderOptions相应的添加对应的SDWebImageDownloaderOptions. downloaderOptions |= SDWebImageDownloaderLowPriority这种表达式的意思等同于 // downloaderOptions = downloaderOptions | SDWebImageDownloaderLowPriority 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 (image && options & SDWebImageRefreshCached) { // force progressive off if image already cached but forced refreshing downloaderOptions &= ~SDWebImageDownloaderProgressiveDownload; // ignore image read from NSURLCache if image if cached but force refreshing downloaderOptions |= SDWebImageDownloaderIgnoreCachedResponse; } // 调用imageDownloader去下载image并且返回执行这个request的download的operation id subOperation = [self.imageDownloader downloadImageWithURL:url options:downloaderOptions progress:progressBlock completed:^(UIImage *downloadedImage, NSData *data, NSError *error, BOOL finished) { if (weakOperation.isCancelled) { // Do nothing if the operation was cancelled // 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 } else if (error) { dispatch_main_sync_safe(^{ if (!weakOperation.isCancelled) { completedBlock(nil, error, SDImageCacheTypeNone, finished, url); } }); if (error.code != NSURLErrorNotConnectedToInternet && error.code != NSURLErrorCancelled && error.code != NSURLErrorTimedOut) { @synchronized (self.failedURLs) { [self.failedURLs addObject:url]; } } } else { if ((options & SDWebImageRetryFailed)) { @synchronized (self.failedURLs) { [self.failedURLs removeObject:url]; } } BOOL cacheOnDisk = !(options & SDWebImageCacheMemoryOnly); if (options & SDWebImageRefreshCached && image && !downloadedImage) { // Image refresh hit the NSURLCache cache, do not call the completion block } else if (downloadedImage && (!downloadedImage.images || (options & SDWebImageTransformAnimatedImage)) && [self.delegate respondsToSelector:@selector(imageManager:transformDownloadedImage:withURL:)]) { dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{ UIImage *transformedImage = [self.delegate imageManager:self transformDownloadedImage:downloadedImage withURL:url]; if (transformedImage && finished) { BOOL imageWasTransformed = ![transformedImage isEqual:downloadedImage]; [self.imageCache storeImage:transformedImage recalculateFromImage:imageWasTransformed imageData:data forKey:key toDisk:cacheOnDisk]; } dispatch_main_sync_safe(^{ if (!weakOperation.isCancelled) { completedBlock(transformedImage, nil, SDImageCacheTypeNone, finished, url); } }); }); } else { if (downloadedImage && finished) { [self.imageCache storeImage:downloadedImage recalculateFromImage:NO imageData:data forKey:key toDisk:cacheOnDisk]; } dispatch_main_sync_safe(^{ if (!weakOperation.isCancelled) { completedBlock(downloadedImage, nil, SDImageCacheTypeNone, finished, url); } }); } } if (finished) { @synchronized (self.runningOperations) { [self.runningOperations removeObject:operation]; } } }]; operation.cancelBlock = ^{ [subOperation cancel]; @synchronized (self.runningOperations) { [self.runningOperations removeObject:weakOperation]; } }; } else if (image) { dispatch_main_sync_safe(^{ if (!weakOperation.isCancelled) { completedBlock(image, nil, cacheType, YES, url); } }); @synchronized (self.runningOperations) { [self.runningOperations removeObject:operation]; } } else { // Image not in cache and download disallowed by delegate dispatch_main_sync_safe(^{ if (!weakOperation.isCancelled) { completedBlock(nil, nil, SDImageCacheTypeNone, YES, url); } }); @synchronized (self.runningOperations) { [self.runningOperations removeObject:operation]; } } }]; return operation;}- (void)saveImageToCache:(UIImage *)image forURL:(NSURL *)url { if (image && url) { NSString *key = [self cacheKeyForURL:url]; [self.imageCache storeImage:image forKey:key toDisk:YES]; }}// cancel掉所有正在执行的operation- (void)cancelAll { @synchronized (self.runningOperations) { NSArray *copiedOperations = [self.runningOperations copy]; [copiedOperations makeObjectsPerformSelector:@selector(cancel)]; [self.runningOperations removeObjectsInArray:copiedOperations]; }}// 判断是否有正在运行的operation- (BOOL)isRunning { return self.runningOperations.count > 0;}@end@implementation SDWebImageCombinedOperation- (void)setCancelBlock:(SDWebImageNoParamsBlock)cancelBlock { // check if the operation is already cancelled, then we just call the cancelBlock if (self.isCancelled) { if (cancelBlock) { cancelBlock(); } _cancelBlock = nil; // don't forget to nil the cancelBlock, otherwise we will get crashes } else { _cancelBlock = [cancelBlock copy]; }}- (void)cancel { self.cancelled = YES; if (self.cacheOperation) { [self.cacheOperation cancel]; self.cacheOperation = nil; } if (self.cancelBlock) { self.cancelBlock(); // TODO: this is a temporary fix to #809. // Until we can figure the exact cause of the crash, going with the ivar instead of the setter// self.cancelBlock = nil; _cancelBlock = nil; }}@end@implementation SDWebImageManager (Deprecated)// deprecated method, uses the non deprecated method// adapter for the completion block- (id )downloadWithURL:(NSURL *)url options:(SDWebImageOptions)options progress:(SDWebImageDownloaderProgressBlock)progressBlock completed:(SDWebImageCompletedWithFinishedBlock)completedBlock { return [self downloadImageWithURL:url options:options progress:progressBlock completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) { if (completedBlock) { completedBlock(image, error, cacheType, finished); } }];}@end下面来简单的解释一下OC里枚举的两种类型.
NS_ENUM和NS_OPTIONS
本质上是一样的都是枚举.
我举个例子.
typedef NS_ENUM(NSInteger, UIViewAnimationTransition) { UIViewAnimationTransitionNone, UIViewAnimationTransitionFlipFromLeft, UIViewAnimationTransitionFlipFromRight, UIViewAnimationTransitionCurlUp, UIViewAnimationTransitionCurlDown,};typedef NS_OPTIONS(NSUInteger, UIViewAutoresizing) { UIViewAutoresizingNone = 0, UIViewAutoresizingFlexibleLeftMargin = 1 << 0, UIViewAutoresizingFlexibleWidth = 1 << 1, UIViewAutoresizingFlexibleRightMargin = 1 << 2, UIViewAutoresizingFlexibleTopMargin = 1 << 3, UIViewAutoresizingFlexibleHeight = 1 << 4, UIViewAutoresizingFlexibleBottomMargin = 1 << 5};应该可以看出一些苗头.
NS_ENUM这种声明出来的东西大部分是单选. NS_OPTIONS声明出来的大部分是多选.
像UIViewAnimationTransition这种在用的时候肯定是只能选一种效果,你要么从左翻到右,要么从右翻到左,你做动画的时候总不能同一时刻让他同时从左到右,又从右到左翻,对吧.
而UIViewAutosizing就不一样了.我要是让子view的宽高和父View一样,那么autoviewsizing的选项肯定是类似于这种.UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight
没错吧,意思就是两个options的我都得选才行.
那么如果有个场景让我判断当前的view的Autoresizing有哪几个.我怎么判断呢?
很简单.用按位与操作就行了.
假设 autoResizings = UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleRightMargin;
我们判断autoResizings里是否有UIViewAutoresizingFlexibleLeftMargin的时候只需要if(autoResizings & UIViewAutoresizingFlexibleLeftMargin)是否为true就可以了.
用二进制表示的话(这里不用care NSUInteger到底是几位的.就表示这么个意思)
UIViewAutoresizingFlexibleLeftMargin = 00000001UIViewAutoresizingFlexibleWidth = 00000010UIViewAutoresizingFlexibleRightMargin = 00000100所以根据上面的表达式,我们的autoResizings = 00000111.
那么执行按位与操作是这样的.
00000111&00000001 结果就是00000001,为true.表示含有这个选项.作为一个开发者，有一个学习的氛围跟一个交流圈子特别重要，这是一个我的iOS交流群：519832104 不管你是小白还是大牛欢迎入驻，分享经验，讨论技术，大家一起交流学习成长！
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SDWebImage源码解析之SDWebImageManager的注解
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