SDWebImage 5.0.1版本 深度解析
地址 github.com/SDWebImage/…git
首先我以爲應該對該框架有一個宏觀層面的瞭解，根據這個思路，層層去分析。github
加載流程
咱們看到大體上還有如下的流程。web
1.調用- (void)sd_setImageWithURL:(nullable NSURL *)url（相似的方法有不少種，在UIImageView+WebCache文件中）。數組
2.進入🤝口sd_internalSetImageWithURL（在UIView+WebCach文件中e）。瀏覽器
3.下載圖片。緩存
4.下載以前，先去查找圖片（經過url，先查緩存後查磁盤，也能夠設置查不查緩存）。安全
5.若是有的話，返回結果。bash
6.真正的去下載圖片cookie
7.返回下載的結果。網絡
8.將下載的圖片存在磁盤和緩存中（能夠設置是否存到緩存）。
麻辣雞上次寫的東西 存不上 都沒了、、。從寫一遍吧
一些要記住的枚舉 和 常量##
枚舉採用位運算的方式，能夠選擇多個用 | 隔開。關於位運算，以後再寫。 註釋寫的很清楚了，能夠本身看。
typedef NS_OPTIONS(NSUInteger, SDWebImageOptions) {
失敗重試，有一個加載失敗的url數組。每次都在數組中查詢一下，
若是設置失敗重試了，就開始下載。若是設置了失敗不重試，就不下載。
SDWebImageRetryFailed = 1 << 0,
低優先級
SDWebImageLowPriority = 1 << 1,
只在保存到內存中
SDWebImageCacheMemoryOnly = 1 << 2,
漸進下載，相似於瀏覽器的的方式。
SDWebImageProgressiveDownload = 1 << 3,
刷新內存，下完完成以後進行比對，若是圖片變了 就刷新緩存中的圖片。
SDWebImageRefreshCached = 1 << 4,
後臺下載，當設置了後臺操做的時候，就會自動進行，超期了自動中止
SDWebImageContinueInBackground = 1 << 5,
設置cookies 不知道幹啥用的。。
SDWebImageHandleCookies = 1 << 6,
容許無效的證書，若是url是https的，可是沒有證書的話，用這個選項。
SDWebImageAllowInvalidSSLCertificates = 1 << 7,
高優先級
SDWebImageHighPriority = 1 << 8,
延遲設置佔位圖
SDWebImageDelayPlaceholder = 1 << 9,
轉換動畫圖片，當設置了這個，全部的動畫圖片都會被轉換。
SDWebImageTransformAnimatedImage = 1 << 10,
取消下載完成以後 自動設置圖片。
SDWebImageAvoidAutoSetImage = 1 << 11,
取消自動縮放，
SDWebImageScaleDownLargeImages = 1 << 12,
當圖片在內存中的時候 也去同步查找磁盤。
SDWebImageQueryDataWhenInMemory = 1 << 13,
一般查找磁盤是異步的，能夠設置成同步的。
SDWebImageQueryDiskSync = 1 << 14,
只從內存中查找圖片
SDWebImageFromCacheOnly = 1 << 15,
轉換圖片，好比 webp轉成png。
SDWebImageForceTransition = 1 << 16
};
typedef NS_OPTIONS(NSUInteger, SDWebImageDownloaderOptions) {
低優先級
SDWebImageDownloaderLowPriority = 1 << 0,
漸進下載
SDWebImageDownloaderProgressiveDownload = 1 << 1,
使用NSURLCache 不知道幹啥的，。
SDWebImageDownloaderUseNSURLCache = 1 << 2,
無視NSURLCache的響應數據
SDWebImageDownloaderIgnoreCachedResponse = 1 << 3,
後臺下載
SDWebImageDownloaderContinueInBackground = 1 << 4,
設置cookies
SDWebImageDownloaderHandleCookies = 1 << 5,
容許無效的證書
SDWebImageDownloaderAllowInvalidSSLCertificates = 1 << 6,
高優先級
SDWebImageDownloaderHighPriority = 1 << 7,
自動縮放
SDWebImageDownloaderScaleDownLargeImages = 1 << 8,
};
typedef NS_ENUM(NSInteger, SDWebImageDownloaderExecutionOrder) {
隊列數據結構 先進先出
(first-in-first-out).
SDWebImageDownloaderFIFOExecutionOrder,
棧結構 後進先出
(last-in-first-out).
SDWebImageDownloaderLIFOExecutionOrder
};
typedef NS_ENUM(NSInteger, SDImageCacheType) {
不緩存
SDImageCacheTypeNone,
磁盤緩存
SDImageCacheTypeDisk,
內存緩存
SDImageCacheTypeMemory
};
typedef NS_OPTIONS(NSUInteger, SDImageCacheOptions) {
在內存中的時候，也去同步查找存盤
SDImageCacheQueryDataWhenInMemory = 1 << 0,
同步去查查找磁盤
SDImageCacheQueryDiskSync = 1 << 1,
取消自動縮放
SDImageCacheScaleDownLargeImages = 1 << 2
};
SD_UIKIT
// iOS and tvOS are very similar, UIKit exists on both platforms
#if TARGET_OS_IOS || TARGET_OS_TV
#define SD_UIKIT 1
#else
#define SD_UIKIT 0
#endif
信號量當作鎖來用
#define LOCK(lock) dispatch_semaphore_wait(lock, DISPATCH_TIME_FOREVER);
#define UNLOCK(lock) dispatch_semaphore_signal(lock);
複製代碼
幾個關鍵的類 簡要說明##
SDImageCache 緩存類
內存緩存採用的是NSCache 和 NSMapTable結合的方式。由於NSCache有的時候會自動釋放，不受控制。我猜NSMapTable是拉鍊法的散列表。
YYCache也是繼承NSCache，可是是用本身實現的雙向鏈表來完成自定義的內存緩存。
SDWebImageDownloader 下載類
SDWebImageManager 核心類
這個類 是下載和查找的入口。是sd的靈魂。
UIView+WebCache UI層面調用的入口 不論是imageView button，最後都會調用到這裏。
根據流程一行一行代碼的看
- (void)sd_setImageWithURL:(nullable NSURL *)url
placeholderImage:(nullable UIImage *)placeholder
options:(SDWebImageOptions)options
progress:(nullable SDWebImageDownloaderProgressBlock)progressBlock
completed:(nullable SDExternalCompletionBlock)completedBlock;
參數沒有什麼好說的了。
最終會調用如下方法
代碼段1
- (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
context:(nullable NSDictionary<NSString *, id> *)context {
//設置validOperationKey
NSString *validOperationKey = operationKey ?: NSStringFromClass([self class]);
//經過validOperationKey 看有沒有在下載的隊列中，若是在的話，就取消下載而且從隊列中移除。這裏用了同步鎖來保存線程安安全。
[self sd_cancelImageLoadOperationWithKey:validOperationKey];
綁定新的url
objc_setAssociatedObject(self, &imageURLKey, url, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
//& 位運算 不知道的同窗查找 按位與 就能夠了
//若是沒有設置延遲設置佔位圖的話 就馬上設置佔位圖。
if (!(options & SDWebImageDelayPlaceholder)) {
dispatch_main_async_safe(^{
//若是設置了回調 就經過回調把佔位圖傳回去，若果沒設置block
判斷是否是UIImageView，是的話就直接設置。
[self sd_setImage:placeholder imageData:nil basedOnClassOrViaCustomSetImageBlock:setImageBlock];
});
}
if (url) {
#if SD_UIKIT
//若是設置了顯示系統菊花，就顯示出來。
if ([self sd_showActivityIndicatorView]) {
[self sd_addActivityIndicator];
}
#endif
// 重置進度
self.sd_imageProgress.totalUnitCount = 0;
self.sd_imageProgress.completedUnitCount = 0;
SDWebImageManager *manager;
//若是設置了單例mananger以外的mananger就取出來，賦值。
//sd是容許使用其餘方式初始化的manager的。
if ([context valueForKey:SDWebImageExternalCustomManagerKey]) {
manager = (SDWebImageManager *)[context valueForKey:SDWebImageExternalCustomManagerKey];
} else {
//若是沒有設置額外的manager ，就獲取單例。
manager = [SDWebImageManager sharedManager];
}
__weak __typeof(self)wself = self;
//進度的block回調
SDWebImageDownloaderProgressBlock combinedProgressBlock = ^(NSInteger receivedSize, NSInteger expectedSize, NSURL * _Nullable targetURL) {
wself.sd_imageProgress.totalUnitCount = expectedSize;
wself.sd_imageProgress.completedUnitCount = receivedSize;
//若是設置了進度block 就回調回去
if (progressBlock) {
progressBlock(receivedSize, expectedSize, targetURL);
}
};
//這個方法的代碼在下一段中貼出來說解。
//能夠理解爲已經獲得了圖片。
id <SDWebImageOperation> operation = [manager loadImageWithURL:url options:options progress:combinedProgressBlock completed:^(UIImage *image, NSData *data, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
__strong __typeof (wself) sself = wself;
if (!sself) { return; }
#if SD_UIKIT
//移除菊花
[sself sd_removeActivityIndicator];
#endif
// if the progress not been updated, mark it to complete state
//若是完成了。且沒有錯誤且總數=0.且完成=0，就把進度和數量設置爲位置的。真的很嚴謹。
if (finished && !error && sself.sd_imageProgress.totalUnitCount == 0 && sself.sd_imageProgress.completedUnitCount == 0) {
sself.sd_imageProgress.totalUnitCount = SDWebImageProgressUnitCountUnknown;
sself.sd_imageProgress.completedUnitCount = SDWebImageProgressUnitCountUnknown;
}
//看設置了取消自動賦值嗎
BOOL shouldCallCompletedBlock = finished || (options & SDWebImageAvoidAutoSetImage);
//看 需不須要自動賦值
//第一個判斷條件。有圖片且取消了自動賦值
//第二個判斷條件。沒圖片且沒有設置延遲設置佔位圖
BOOL shouldNotSetImage = ((image && (options & SDWebImageAvoidAutoSetImage)) ||
(!image && !(options & SDWebImageDelayPlaceholder)));
SDWebImageNoParamsBlock callCompletedBlockClojure = ^{
if (!sself) { return; }
//要自動設置圖片
if (!shouldNotSetImage) {
//把這個view設置成NeedsLayout，在下一個對應mode的Runloop循環的時候，會去從新計算。
[sself sd_setNeedsLayout];
}
//若是須要回調。
if (completedBlock && shouldCallCompletedBlock) {
completedBlock(image, error, cacheType, url);
}
};
// case 1a: we got an image, but the SDWebImageAvoidAutoSetImage flag is set
// OR
// case 1b: we got no image and the SDWebImageDelayPlaceholder is not set
if (shouldNotSetImage) {
//若是不用去設置圖片 調用block 結束了
dispatch_main_async_safe(callCompletedBlockClojure);
return;
}
UIImage *targetImage = nil;
NSData *targetData = nil;
if (image) {
// case 2a: we got an image and the SDWebImageAvoidAutoSetImage is not set
//解釋的很清楚了。。
targetImage = image;
targetData = data;
} else if (options & SDWebImageDelayPlaceholder) {
// case 2b: we got no image and the
SDWebImageDelayPlaceholder flag is set
//解釋的很清楚了。。
targetImage = placeholder;
targetData = nil;
}
#if SD_UIKIT || SD_MAC
// check whether we should use the image transition
SDWebImageTransition *transition = nil;
//若是設置了圖片轉換或者不緩存，不緩存這個條件我沒懂
if (finished && (options & SDWebImageForceTransition || cacheType == SDImageCacheTypeNone)) {
transition = sself.sd_imageTransition;
}
#endif
dispatch_main_async_safe(^{
#if SD_UIKIT || SD_MAC
//設置圖片，設置了轉換的話 作相應的處理。
[sself sd_setImage:targetImage imageData:targetData basedOnClassOrViaCustomSetImageBlock:setImageBlock transition:transition cacheType:cacheType imageURL:imageURL];
#else
[sself sd_setImage:targetImage imageData:targetData basedOnClassOrViaCustomSetImageBlock:setImageBlock];
#endif
//完成的回調
callCompletedBlockClojure();
});
}];
//處理下載隊列
[self sd_setImageLoadOperation:operation forKey:validOperationKey];
} else {
dispatch_main_async_safe(^{
#if SD_UIKIT
[self sd_removeActivityIndicator];
#endif
if (completedBlock) {
NSError *error = [NSError errorWithDomain:SDWebImageErrorDomain code:-1 userInfo:@{NSLocalizedDescriptionKey : @"Trying to load a nil url"}];
completedBlock(nil, error, SDImageCacheTypeNone, url);
}
});
}
}
複製代碼
代碼段2
這段代碼完成了，查找和下載的操做
- (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
//斷言 參數不符合的話 就崩潰在這裏。
NSAssert(completedBlock != nil, @"If you mean to prefetch the image, use -[SDWebImagePrefetcher prefetchURLs] instead");
//使用者老是有這個錯誤。。。沒辦法。。做者屈服了 加了判斷。
if ([url isKindOfClass:NSString.class]) {
url = [NSURL URLWithString:(NSString *)url];
}
// 保護程序 防止崩潰 null 就炸了。
if (![url isKindOfClass:NSURL.class]) {
url = nil;
}
SDWebImageCombinedOperation *operation = [SDWebImageCombinedOperation new];
operation.manager = self;
//看是否是這個url在不在下載失敗的數組裏
BOOL isFailedUrl = NO;
if (url) {
//用信號量 保證線程安全。
LOCK(self.failedURLsLock);
isFailedUrl = [self.failedURLs containsObject:url];
UNLOCK(self.failedURLsLock);
}
//url 沒有值，失敗不重試，在下載失敗的數組中
if (url.absoluteString.length == 0 || (!(options & SDWebImageRetryFailed) && isFailedUrl)) {
//完成回調 ， 設置error ， 返回結束。
[self callCompletionBlockForOperation:operation completion:completedBlock error:[NSError errorWithDomain:NSURLErrorDomain code:NSURLErrorFileDoesNotExist userInfo:nil] url:url];
return operation;
}
//先鎖，而後再操做隊列中加入本次操做。
LOCK(self.runningOperationsLock);
[self.runningOperations addObject:operation];
UNLOCK(self.runningOperationsLock);
//經過url 返回key，這個轉化規則，能夠自定義規則。
NSString *key = [self cacheKeyForURL:url];
SDImageCacheOptions cacheOptions = 0;
//根據SDWebImageOptions 設置 SDImageCacheOptions。
// cacheOptions|= SDImageCacheQueryDataWhenInMemory 作位或計算，將結果賦值給cacheOptions
// 等價於 cacheOptions = cacheOptions | SDImageCacheQueryDataWhenInMemory；
// 按位或 每一位都進行比較 相同的位都是1 ，結果的那一位就是1.排除其餘的影響。
if (options & SDWebImageQueryDataWhenInMemory) cacheOptions |= SDImageCacheQueryDataWhenInMemory;
if (options & SDWebImageQueryDiskSync) cacheOptions |= SDImageCacheQueryDiskSync;
if (options & SDWebImageScaleDownLargeImages) cacheOptions |= SDImageCacheScaleDownLargeImages;
__weak SDWebImageCombinedOperation *weakOperation = operation;
//去查找緩存 代碼段3詳細說明。這裏能夠先看作已經查到了。
operation.cacheOperation = [self.imageCache queryCacheOperationForKey:key options:cacheOptions done:^(UIImage *cachedImage, NSData *cachedData, SDImageCacheType cacheType) {
__strong __typeof(weakOperation) strongOperation = weakOperation;
if (!strongOperation || strongOperation.isCancelled) {
//若是操做被取消了 就安全的從操做隊列中移除。
[self safelyRemoveOperationFromRunning:strongOperation];
return;
}
// 看需不須要從網絡下載圖片。
//條件1 不是隻從內存中查找。
//條件2 緩存中沒有圖片，或者刷新內存中的圖片
//條件3 設置了下載的代理
BOOL shouldDownload = (!(options & SDWebImageFromCacheOnly))
&& (!cachedImage || options & SDWebImageRefreshCached)
&& (![self.delegate respondsToSelector:@selector(imageManager:shouldDownloadImageForURL:)] || [self.delegate imageManager:self shouldDownloadImageForURL:url]);
//須要下載
if (shouldDownload) {
//若是緩存中有圖片且設置了刷新緩存
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.
//很詳細 不翻譯了
[self callCompletionBlockForOperation:strongOperation completion:completedBlock image:cachedImage data:cachedData error:nil cacheType:cacheType finished:YES url:url];
}
// download if no image or requested to refresh anyway, and download allowed by delegate
SDWebImageDownloaderOptions downloaderOptions = 0;
//根據SDWebImageOptions 設置 SDWebImageDownloaderOptions。
// cacheOptions|= SDImageCacheQueryDataWhenInMemory 作位或計算，將結果賦值給cacheOptions
// 等價於 cacheOptions = cacheOptions | SDImageCacheQueryDataWhenInMemory；
// 按位或 每一位都進行比較 相同的位都是1 ，結果的那一位就是1.排除其餘的影響。
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
//downloaderOptions = ~(downloaderOptions & SDWebImageDownloaderProgressiveDownload)取反
downloaderOptions &= ~SDWebImageDownloaderProgressiveDownload;
// ignore image read from NSURLCache if image if cached but force refreshing
downloaderOptions |= SDWebImageDownloaderIgnoreCachedResponse;
}
// `SDWebImageCombinedOperation` -> `SDWebImageDownloadToken` -> `downloadOperationCancelToken`, which is a `SDCallbacksDictionary` and retain the completed block below, so we need weak-strong again to avoid retain cycle
__weak typeof(strongOperation) weakSubOperation = strongOperation;
//真正開始下載
strongOperation.downloadToken = [self.imageDownloader downloadImageWithURL:url options:downloaderOptions progress:progressBlock completed:^(UIImage *downloadedImage, NSData *downloadedData, NSError *error, BOOL finished) {
__strong typeof(weakSubOperation) strongSubOperation = weakSubOperation;
//下載操做取消了 什麼也不作 github的ieesu 699 有詳細說明
if (!strongSubOperation || strongSubOperation.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) {
//錯誤了 返回
[self callCompletionBlockForOperation:strongSubOperation completion:completedBlock error:error url:url];
BOOL shouldBlockFailedURL;
// Check whether we should block failed url
//若是須要返回錯誤的url
if ([self.delegate respondsToSelector:@selector(imageManager:shouldBlockFailedURL:withError:)]) {
shouldBlockFailedURL = [self.delegate imageManager:self shouldBlockFailedURL:url withError:error];
} else {
//看是否有任何錯誤
shouldBlockFailedURL = ( error.code != NSURLErrorNotConnectedToInternet
&& error.code != NSURLErrorCancelled
&& error.code != NSURLErrorTimedOut
&& error.code != NSURLErrorInternationalRoamingOff
&& error.code != NSURLErrorDataNotAllowed
&& error.code != NSURLErrorCannotFindHost
&& error.code != NSURLErrorCannotConnectToHost
&& error.code != NSURLErrorNetworkConnectionLost);
}
if (shouldBlockFailedURL) {
LOCK(self.failedURLsLock);
//添加到失敗url的數組
[self.failedURLs addObject:url];
UNLOCK(self.failedURLsLock);
}
}
//沒有錯誤
else {
//設置了失敗重試的話 ，把url 從失敗的數組中移除。
if ((options & SDWebImageRetryFailed)) {
LOCK(self.failedURLsLock);
[self.failedURLs removeObject:url];
UNLOCK(self.failedURLsLock);
}
//是否緩存到磁盤中 只有設置了SDWebImageCacheMemoryOnly 纔不存到磁盤。
BOOL cacheOnDisk = !(options & SDWebImageCacheMemoryOnly);
// We are done the scale process in SDWebImageDownloader with the shared manager, this is used for custom manager and avoid extra scale.
//下載過程當中，已經進行了縮放，若是有自定義的manager ，避免重複的縮放。
if (self != [SDWebImageManager sharedManager] && self.cacheKeyFilter && downloadedImage) {
downloadedImage = [self scaledImageForKey:key image:downloadedImage];
}
//NSURLCache 緩存命中
if (options & SDWebImageRefreshCached && cachedImage && !downloadedImage) {
// Image refresh hit the NSURLCache cache, do not call the completion block
//若是圖片下載完成 且 下載的圖片只有一個 或者 設置了SDWebImageTransformAnimatedImage
} else if (downloadedImage && (!downloadedImage.images || (options & SDWebImageTransformAnimatedImage)) && [self.delegate respondsToSelector:@selector(imageManager:transformDownloadedImage:withURL:)]) {
//出來圖片轉換以後的狀況
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
UIImage *transformedImage = [self.delegate imageManager:self transformDownloadedImage:downloadedImage withURL:url];
if (transformedImage && finished) {
//檢查圖片有沒有被編輯過
BOOL imageWasTransformed = ![transformedImage isEqual:downloadedImage];
NSData *cacheData;
// pass nil if the image was transformed, so we can recalculate the data from the image
// 若是設置了全局的解析轉換
if (self.cacheSerializer) {
cacheData = self.cacheSerializer(transformedImage, (imageWasTransformed ? nil : downloadedData), url);
} else {
cacheData = (imageWasTransformed ? nil : downloadedData);
}
//緩存 請看代碼段4
[self.imageCache storeImage:transformedImage imageData:cacheData forKey:key toDisk:cacheOnDisk completion:nil];
}
//完成的block回調
[self callCompletionBlockForOperation:strongSubOperation completion:completedBlock image:transformedImage data:downloadedData error:nil cacheType:SDImageCacheTypeNone finished:finished url:url];
});
} else {
//下載圖片成功 且 完成
if (downloadedImage && finished) {
if (self.cacheSerializer) {
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0), ^{
NSData *cacheData = self.cacheSerializer(downloadedImage, downloadedData, url);
[self.imageCache storeImage:downloadedImage imageData:cacheData forKey:key toDisk:cacheOnDisk completion:nil];
});
} else {
//保存內存和磁盤
[self.imageCache storeImage:downloadedImage imageData:downloadedData forKey:key toDisk:cacheOnDisk completion:nil];
}
}
[self callCompletionBlockForOperation:strongSubOperation completion:completedBlock image:downloadedImage data:downloadedData error:nil cacheType:SDImageCacheTypeNone finished:finished url:url];
}
}
if (finished) {
[self safelyRemoveOperationFromRunning:strongSubOperation];
}
}];
//圖片在內存中
} else if (cachedImage) {
[self callCompletionBlockForOperation:strongOperation completion:completedBlock image:cachedImage data:cachedData error:nil cacheType:cacheType finished:YES url:url];
[self safelyRemoveOperationFromRunning:strongOperation];
} else {
// Image not in cache and download disallowed by delegate
[self callCompletionBlockForOperation:strongOperation completion:completedBlock image:nil data:nil error:nil cacheType:SDImageCacheTypeNone finished:YES url:url];
[self safelyRemoveOperationFromRunning:strongOperation];
}
}];
return operation;
}
複製代碼
代碼段3 下載
- (nullable SDWebImageDownloadToken *)downloadImageWithURL:(nullable NSURL *)url
options:(SDWebImageDownloaderOptions)options
progress:(nullable SDWebImageDownloaderProgressBlock)progressBlock
completed:(nullable SDWebImageDownloaderCompletedBlock)completedBlock {
__weak SDWebImageDownloader *wself = self;
return [self addProgressCallback:progressBlock completedBlock:completedBlock forURL:url createCallback:^SDWebImageDownloaderOperation *{
__strong __typeof (wself) sself = wself;
NSTimeInterval timeoutInterval = sself.downloadTimeout;
if (timeoutInterval == 0.0) {
timeoutInterval = 15.0;
}
// In order to prevent from potential duplicate caching (NSURLCache + SDImageCache) we disable the cache for image requests if told otherwise
NSURLRequestCachePolicy cachePolicy = options & SDWebImageDownloaderUseNSURLCache ? NSURLRequestUseProtocolCachePolicy : NSURLRequestReloadIgnoringLocalCacheData;
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url
cachePolicy:cachePolicy
timeoutInterval:timeoutInterval];
request.HTTPShouldHandleCookies = (options & SDWebImageDownloaderHandleCookies);
request.HTTPShouldUsePipelining = YES;
if (sself.headersFilter) {
request.allHTTPHeaderFields = sself.headersFilter(url, [sself allHTTPHeaderFields]);
}
else {
request.allHTTPHeaderFields = [sself allHTTPHeaderFields];
}
SDWebImageDownloaderOperation *operation = [[sself.operationClass alloc] initWithRequest:request inSession:sself.session options:options];
operation.shouldDecompressImages = sself.shouldDecompressImages;
if (sself.urlCredential) {
operation.credential = sself.urlCredential;
} else if (sself.username && sself.password) {
operation.credential = [NSURLCredential credentialWithUser:sself.username password:sself.password persistence:NSURLCredentialPersistenceForSession];
}
if (options & SDWebImageDownloaderHighPriority) {
operation.queuePriority = NSOperationQueuePriorityHigh;
} else if (options & SDWebImageDownloaderLowPriority) {
operation.queuePriority = NSOperationQueuePriorityLow;
}
if (sself.executionOrder == SDWebImageDownloaderLIFOExecutionOrder) {
// Emulate LIFO execution order by systematically adding new operations as last operation's dependency [sself.lastAddedOperation addDependency:operation]; sself.lastAddedOperation = operation; } return operation; }]; } 複製代碼
代碼段4 緩存
- (void)storeImage:(nullable UIImage *)image
imageData:(nullable NSData *)imageData
forKey:(nullable NSString *)key
toDisk:(BOOL)toDisk
completion:(nullable SDWebImageNoParamsBlock)completionBlock {
if (!image || !key) {
if (completionBlock) {
completionBlock();
}
return;
}
// if memory cache is enabled
if (self.config.shouldCacheImagesInMemory) {
//計算大小
NSUInteger cost = SDCacheCostForImage(image);
[self.memCache setObject:image forKey:key cost:cost];
}
if (toDisk) {
//ioQueue 隊列 先進先出 一個一個來 保證順序
dispatch_async(self.ioQueue, ^{
@autoreleasepool {
NSData *data = imageData;
if (!data && image) {
// If we do not have any data to detect image format, check whether it contains alpha channel to use PNG or JPEG format
SDImageFormat format;
if (SDCGImageRefContainsAlpha(image.CGImage)) {
format = SDImageFormatPNG;
} else {
format = SDImageFormatJPEG;
}
data = [[SDWebImageCodersManager sharedInstance] encodedDataWithImage:image format:format];
}
[self _storeImageDataToDisk:data forKey:key];
}
if (completionBlock) {
dispatch_async(dispatch_get_main_queue(), ^{
completionBlock();
});
}
});
} else {
if (completionBlock) {
completionBlock();
}
}
}
複製代碼
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