/*
?*?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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