SDWebImage源码解析之SDWebImageManager的注解
/*
* 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:
*
* @code
SDWebImageManager *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 - Deprecated
typedef 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 = 00000001
UIViewAutoresizingFlexibleWidth = 00000010
UIViewAutoresizingFlexibleRightMargin = 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.
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