一、总览
本类继承自 NSOperation，每一张图片的下载对应一个 Operation。
二、头文件提供的属性及方法
SDWebImageDownloaderOperationInterface 协议，SDWebImageDownloaderOperation 遵守该协议，它一共有四个必须实现的方法，可以为自定义的下载操作统一接口。
/**
Describes a downloader operation. If one wants to use a custom downloader op, it needs to inherit from `NSOperation` and conform to this protocol
*/
@protocol SDWebImageDownloaderOperationInterface
- (nonnull instancetype)initWithRequest:(nullable NSURLRequest *)request
inSession:(nullable NSURLSession *)session
options:(SDWebImageDownloaderOptions)options;
- (nullable id)addHandlersForProgress:(nullable SDWebImageDownloaderProgressBlock)progressBlock
completed:(nullable SDWebImageDownloaderCompletedBlock)completedBlock;
- (BOOL)shouldDecompressImages;
- (void)setShouldDecompressImages:(BOOL)value;
- (nullable NSURLCredential *)credential;
- (void)setCredential:(nullable NSURLCredential *)value;
@end
SDWebImageDownloaderOperation 继承自 NSOperation，使用 NSURLSession 实现图片的下载
@interface SDWebImageDownloaderOperation : NSOperation
/**
* The request used by the operation's task.
*/
@property (strong, nonatomic, readonly, nullable) NSURLRequest *request;
/**
* The operation's task
*/
@property (strong, nonatomic, readonly, nullable) NSURLSessionTask *dataTask;
@property (assign, nonatomic) BOOL shouldDecompressImages;
/**
* Was used to determine whether the URL connection should consult the credential storage for authenticating the connection.
* @deprecated Not used for a couple of versions
*/
@property (nonatomic, assign) BOOL shouldUseCredentialStorage __deprecated_msg("Property deprecated. Does nothing. Kept only for backwards compatibility");
/**
* The credential used for authentication challenges in `-connection:didReceiveAuthenticationChallenge:`.
*
* This will be overridden by any shared credentials that exist for the username or password of the request URL, if present.
*/
@property (nonatomic, strong, nullable) NSURLCredential *credential;
/**
* The SDWebImageDownloaderOptions for the receiver.
*/
@property (assign, nonatomic, readonly) SDWebImageDownloaderOptions options;
/**
* The expected size of data.
*/
@property (assign, nonatomic) NSInteger expectedSize;
/**
* The response returned by the operation's connection.
*/
@property (strong, nonatomic, nullable) NSURLResponse *response;
/**
* Initializes a `SDWebImageDownloaderOperation` object
*
* @see SDWebImageDownloaderOperation
*
* @param request the URL request
* @param session the URL session in which this operation will run
* @param options downloader options
*
* @return the initialized instance
*/
- (nonnull instancetype)initWithRequest:(nullable NSURLRequest *)request
inSession:(nullable NSURLSession *)session
options:(SDWebImageDownloaderOptions)options NS_DESIGNATED_INITIALIZER;
/**
* Adds handlers for progress and completion. Returns a tokent that can be passed to -cancel: to cancel this set of
* callbacks.
*
* @param progressBlock the block executed when a new chunk of data arrives.
* @note the progress block is executed on a background queue
* @param completedBlock the block executed when the download is done.
* @note the completed block is executed on the main queue for success. If errors are found, there is a chance the block will be executed on a background queue
*
* @return the token to use to cancel this set of handlers
*/
- (nullable id)addHandlersForProgress:(nullable SDWebImageDownloaderProgressBlock)progressBlock
completed:(nullable SDWebImageDownloaderCompletedBlock)completedBlock;
/**
* Cancels a set of callbacks. Once all callbacks are canceled, the operation is cancelled.
*
* @param token the token representing a set of callbacks to cancel
*
* @return YES if the operation was stopped because this was the last token to be canceled. NO otherwise.
*/
- (BOOL)cancel:(nullable id)token;
@end
三、实现文件
1、私有属性
@interface SDWebImageDownloaderOperation ()
// 回调Block列表
@property (strong, nonatomic, nonnull) NSMutableArray *callbackBlocks;
// 自定义并行Operation需要管理的两个属性。默认是readonly的，我们这里通过声明改为可修改的。方便我们在后面操作。
@property (assign, nonatomic, getter = isExecuting) BOOL executing;
@property (assign, nonatomic, getter = isFinished) BOOL finished;
// 存储图片数据
@property (strong, nonatomic, nullable) NSMutableData *imageData;
// 通过SDWebImageDownloader传过来。所以这里是weak。因为他是通过SDWebImageDownloader管理的。
@property (weak, nonatomic, nullable) NSURLSession *unownedSession;
// 如果unownedSession是nil，我们需要手动创建一个并且管理他的生命周期和代理方法
@property (strong, nonatomic, nullable) NSURLSession *ownedSession;
// dataTask对象
@property (strong, nonatomic, readwrite, nullable) NSURLSessionTask *dataTask;
// 一个并行queue。用于控制数据的处理
@property (SDDispatchQueueSetterSementics, nonatomic, nullable) dispatch_queue_t barrierQueue;
#if SD_UIKIT
// 如果用户设置了后台继续加载选项。则通过backgroundTask来继续下载图片
@property (assign, nonatomic) UIBackgroundTaskIdentifier backgroundTaskId;
#endif
@end
2、实现
@implementation SDWebImageDownloaderOperation {
size_t width, height;
#if SD_UIKIT || SD_WATCH
UIImageOrientation orientation;
#endif
}
@synthesize executing = _executing;
@synthesize finished = _finished;
- (nonnull instancetype)init {
return [self initWithRequest:nil inSession:nil options:0];
}
- (nonnull instancetype)initWithRequest:(nullable NSURLRequest *)request
inSession:(nullable NSURLSession *)session
options:(SDWebImageDownloaderOptions)options {
if ((self = [super init])) {
_request = [request copy];
_shouldDecompressImages = YES;
_options = options;
_callbackBlocks = [NSMutableArray new];
//默认情况下。_executing和finished都是NO
_executing = NO;
_finished = NO;
_expectedSize = 0;
_unownedSession = session;
_barrierQueue = dispatch_queue_create("com.hackemist.SDWebImageDownloaderOperationBarrierQueue", DISPATCH_QUEUE_CONCURRENT);
}
return self;
}
- (void)dealloc {
SDDispatchQueueRelease(_barrierQueue);
}
/**
给Operation添加进度和回调Block
@param progressBlock 进度Block
@param completedBlock 回调Block
@return 回调字典
*/
- (nullable id)addHandlersForProgress:(nullable SDWebImageDownloaderProgressBlock)progressBlock
completed:(nullable SDWebImageDownloaderCompletedBlock)completedBlock {
SDCallbacksDictionary *callbacks = [NSMutableDictionary new];
// 把Operation对应的回调和进度Block存入一个字典中
if (progressBlock) callbacks[kProgressCallbackKey] = [progressBlock copy];
if (completedBlock) callbacks[kCompletedCallbackKey] = [completedBlock copy];
// 把完成和进度Block加入callbackBlocks中
dispatch_barrier_async(self.barrierQueue, ^{
[self.callbackBlocks addObject:callbacks];
});
return callbacks;
}
- (nullable NSArray *)callbacksForKey:(NSString *)key {
__block NSMutableArray *callbacks = nil;
dispatch_sync(self.barrierQueue, ^{
// We need to remove [NSNull null] because there might not always be a progress block for each callback
callbacks = [[self.callbackBlocks valueForKey:key] mutableCopy];
[callbacks removeObjectIdenticalTo:[NSNull null]];
});
return [callbacks copy]; // strip mutability here
}
- (BOOL)cancel:(nullable id)token {
__block BOOL shouldCancel = NO;
dispatch_barrier_sync(self.barrierQueue, ^{
[self.callbackBlocks removeObjectIdenticalTo:token];
if (self.callbackBlocks.count == 0) {
shouldCancel = YES;
}
});
if (shouldCancel) {
[self cancel];
}
return shouldCancel;
}
// 并行的Operation需要重写这个方法.在这个方法里面做具体的处理
- (void)start {
@synchronized (self) {
if (self.isCancelled) {
self.finished = YES;
[self reset];
return;
}
#if SD_UIKIT
Class UIApplicationClass = NSClassFromString(@"UIApplication");
BOOL hasApplication = UIApplicationClass && [UIApplicationClass respondsToSelector:@selector(sharedApplication)];
// 如果用户设置了Background模式，则设置一个backgroundTask
if (hasApplication && [self shouldContinueWhenAppEntersBackground]) {
__weak __typeof__ (self) wself = self;
UIApplication * app = [UIApplicationClass performSelector:@selector(sharedApplication)];
self.backgroundTaskId = [app beginBackgroundTaskWithExpirationHandler:^{
// background结束以后。做清理工作
__strong __typeof (wself) sself = wself;
if (sself) {
[sself cancel];
[app endBackgroundTask:sself.backgroundTaskId];
sself.backgroundTaskId = UIBackgroundTaskInvalid;
}
}];
}
#endif
NSURLSession *session = self.unownedSession;
// 如果SDWebImageDownloader传入的session是nil，则自己手动初始化一个。
if (!self.unownedSession) {
NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration defaultSessionConfiguration];
sessionConfig.timeoutIntervalForRequest = 15;
/**
* Create the session for this task
* We send nil as delegate queue so that the session creates a serial operation queue for performing all delegate
* method calls and completion handler calls.
*/
self.ownedSession = [NSURLSession sessionWithConfiguration:sessionConfig
delegate:self
delegateQueue:nil];
session = self.ownedSession;
}
self.dataTask = [session dataTaskWithRequest:self.request];
self.executing = YES;
}
// 发送请求
[self.dataTask resume];
if (self.dataTask) {
// 第一次调用进度BLOCK
for (SDWebImageDownloaderProgressBlock progressBlock in [self callbacksForKey:kProgressCallbackKey]) {
progressBlock(0, NSURLResponseUnknownLength, self.request.URL);
}
dispatch_async(dispatch_get_main_queue(), ^{
[[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadStartNotification object:self];
});
} else {
[self callCompletionBlocksWithError:[NSError errorWithDomain:NSURLErrorDomain code:0 userInfo:@{NSLocalizedDescriptionKey : @"Connection can't be initialized"}]];
}
#if SD_UIKIT
Class UIApplicationClass = NSClassFromString(@"UIApplication");
if(!UIApplicationClass || ![UIApplicationClass respondsToSelector:@selector(sharedApplication)]) {
return;
}
if (self.backgroundTaskId != UIBackgroundTaskInvalid) {
UIApplication * app = [UIApplication performSelector:@selector(sharedApplication)];
[app endBackgroundTask:self.backgroundTaskId];
self.backgroundTaskId = UIBackgroundTaskInvalid;
}
#endif
}
/**
如果要取消一个Operation，就会调用这个方法。
*/
- (void)cancel {
@synchronized (self) {
[self cancelInternal];
}
}
- (void)cancelInternal {
if (self.isFinished) return;
[super cancel];
if (self.dataTask) {
[self.dataTask cancel];
dispatch_async(dispatch_get_main_queue(), ^{
[[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadStopNotification object:self];
});
// As we cancelled the connection, its callback won't be called and thus won't
// maintain the isFinished and isExecuting flags.
// 更新状态
if (self.isExecuting) self.executing = NO;
if (!self.isFinished) self.finished = YES;
}
[self reset];
}
- (void)done {
self.finished = YES;
self.executing = NO;
[self reset];
}
- (void)reset {
dispatch_barrier_async(self.barrierQueue, ^{
[self.callbackBlocks removeAllObjects];
});
self.dataTask = nil;
self.imageData = nil;
if (self.ownedSession) {
[self.ownedSession invalidateAndCancel];
self.ownedSession = nil;
}
}
/**
需要手动触发_finished的KVO。这个是自定义并发`NSOperation`必须实现的。
@param finished 改变状态
*/
- (void)setFinished:(BOOL)finished {
[self willChangeValueForKey:@"isFinished"];
_finished = finished;
[self didChangeValueForKey:@"isFinished"];
}
/**
需要手动触发_executing的KVO。这个是自定义并发`NSOperation`必须实现的。
@param executing 改变状态
*/
- (void)setExecuting:(BOOL)executing {
[self willChangeValueForKey:@"isExecuting"];
_executing = executing;
[self didChangeValueForKey:@"isExecuting"];
}
/**
返回YES，表明这个NSOperation对象是并发的
@return 返回bool值
*/
- (BOOL)isConcurrent {
return YES;
}
#pragma mark NSURLSessionDataDelegate
/*
当一个task接收到返回信息。当所有信息都接收完毕以后，completionHandler会被调用。我们可以在这里取消一个网络请求或者把一个datatask转换为downloadtask。如果没有实现这个代理方法，我们也可以通过task的response属性获取到对应的数据。background模式的uploadtask不会调用这个方法。
*/
- (void)URLSession:(NSURLSession *)session
dataTask:(NSURLSessionDataTask *)dataTask
didReceiveResponse:(NSURLResponse *)response
completionHandler:(void (^)(NSURLSessionResponseDisposition disposition))completionHandler {
//'304 Not Modified' is an exceptional one
if (![response respondsToSelector:@selector(statusCode)] || (((NSHTTPURLResponse *)response).statusCode < 400 && ((NSHTTPURLResponse *)response).statusCode != 304)) {
// 期望的总长度
NSInteger expected = response.expectedContentLength > 0 ? (NSInteger)response.expectedContentLength : 0;
self.expectedSize = expected;
// 进度回调Block
for (SDWebImageDownloaderProgressBlock progressBlock in [self callbacksForKey:kProgressCallbackKey]) {
progressBlock(0, expected, self.request.URL);
}
self.imageData = [[NSMutableData alloc] initWithCapacity:expected];
self.response = response;
dispatch_async(dispatch_get_main_queue(), ^{
[[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadReceiveResponseNotification object:self];
});
}
else {
NSUInteger code = ((NSHTTPURLResponse *)response).statusCode;
//This is the case when server returns '304 Not Modified'. It means that remote image is not changed.
//In case of 304 we need just cancel the operation and return cached image from the cache.
/*
如果返回304表示图片么有变化。在这种情况下，我们只需要取消operation并且返回缓存的图片就可以了。
*/
if (code == 304) {
[self cancelInternal];
} else {
[self.dataTask cancel];
}
dispatch_async(dispatch_get_main_queue(), ^{
[[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadStopNotification object:self];
});
[self callCompletionBlocksWithError:[NSError errorWithDomain:NSURLErrorDomain code:((NSHTTPURLResponse *)response).statusCode userInfo:nil]];
[self done];
}
//这个表示允许继续加载
if (completionHandler) {
completionHandler(NSURLSessionResponseAllow);
}
}
/*
*会被多次调用。获取图片数据
*/
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data {
[self.imageData appendData:data];
if ((self.options & SDWebImageDownloaderProgressiveDownload) && self.expectedSize > 0) {
// The following code is from http://www.cocoaintheshell.com/2011/05/progressive-images-download-imageio/
// Thanks to the author @Nyx0uf
// Get the total bytes downloaded
// 获取已经下载的数据长度
const NSInteger totalSize = self.imageData.length;
// Update the data source, we must pass ALL the data, not just the new bytes
CGImageSourceRef imageSource = CGImageSourceCreateWithData((__bridge CFDataRef)self.imageData, NULL);
/*
*width和height都是0的话表示还么有获取到图片的高度和宽度。我们可以通过数据来获取图片的宽度和高度
*此时表示第一次收到图片数据
*/
if (width + height == 0) {
// 获取图片数据的属性
CFDictionaryRef properties = CGImageSourceCopyPropertiesAtIndex(imageSource, 0, NULL);
if (properties) {
NSInteger orientationValue = -1;
// 获取高度值
CFTypeRef val = CFDictionaryGetValue(properties, kCGImagePropertyPixelHeight);
if (val) CFNumberGetValue(val, kCFNumberLongType, &height);
// 获取宽度值
val = CFDictionaryGetValue(properties, kCGImagePropertyPixelWidth);
if (val) CFNumberGetValue(val, kCFNumberLongType, &width);
// 获取图片的方向值
val = CFDictionaryGetValue(properties, kCGImagePropertyOrientation);
if (val) CFNumberGetValue(val, kCFNumberNSIntegerType, &orientationValue);
CFRelease(properties);
// When we draw to Core Graphics, we lose orientation information,
// which means the image below born of initWithCGIImage will be
// oriented incorrectly sometimes. (Unlike the image born of initWithData
// in didCompleteWithError.) So save it here and pass it on later.
#if SD_UIKIT || SD_WATCH
orientation = [[self class] orientationFromPropertyValue:(orientationValue == -1 ? 1 : orientationValue)];
#endif
}
}
/*
* 这个表示已经收到部分图片数据并且还么有获取到所有的图片数据
*/
if (width + height > 0 && totalSize < self.expectedSize) {
// Create the image
CGImageRef partialImageRef = CGImageSourceCreateImageAtIndex(imageSource, 0, NULL);
#if SD_UIKIT || SD_WATCH
// Workaround for iOS anamorphic image
if (partialImageRef) {
const size_t partialHeight = CGImageGetHeight(partialImageRef);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef bmContext = CGBitmapContextCreate(NULL, width, height, 8, width * 4, colorSpace, kCGBitmapByteOrderDefault | kCGImageAlphaPremultipliedFirst);
CGColorSpaceRelease(colorSpace);
if (bmContext) {
CGContextDrawImage(bmContext, (CGRect){.origin.x = 0.0f, .origin.y = 0.0f, .size.width = width, .size.height = partialHeight}, partialImageRef);
CGImageRelease(partialImageRef);
partialImageRef = CGBitmapContextCreateImage(bmContext);
CGContextRelease(bmContext);
}
else {
CGImageRelease(partialImageRef);
partialImageRef = nil;
}
}
#endif
if (partialImageRef) {
#if SD_UIKIT || SD_WATCH
UIImage *image = [UIImage imageWithCGImage:partialImageRef scale:1 orientation:orientation];
#elif SD_MAC
UIImage *image = [[UIImage alloc] initWithCGImage:partialImageRef size:NSZeroSize];
#endif
// 获取图片url对应的key
NSString *key = [[SDWebImageManager sharedManager] cacheKeyForURL:self.request.URL];
// 根据原始图片数据获取对应scale下面的图片
UIImage *scaledImage = [self scaledImageForKey:key image:image];
// 是否解压缩图片
if (self.shouldDecompressImages) {
/*
*解压缩图片
*/
image = [UIImage decodedImageWithImage:scaledImage];
}
else {
image = scaledImage;
}
CGImageRelease(partialImageRef);
[self callCompletionBlocksWithImage:image imageData:nil error:nil finished:NO];
}
}
CFRelease(imageSource);
}
for (SDWebImageDownloaderProgressBlock progressBlock in [self callbacksForKey:kProgressCallbackKey]) {
progressBlock(self.imageData.length, self.expectedSize, self.request.URL);
}
}
- (void)URLSession:(NSURLSession *)session
dataTask:(NSURLSessionDataTask *)dataTask
willCacheResponse:(NSCachedURLResponse *)proposedResponse
completionHandler:(void (^)(NSCachedURLResponse *cachedResponse))completionHandler {
//根据request的选项。决定是否缓存NSCachedURLResponse
NSCachedURLResponse *cachedResponse = proposedResponse;
if (self.request.cachePolicy == NSURLRequestReloadIgnoringLocalCacheData) {
// Prevents caching of responses
cachedResponse = nil;
}
if (completionHandler) {
completionHandler(cachedResponse);
}
}
#pragma mark NSURLSessionTaskDelegate
/*
网络请求加载完成，在这里处理获得的数据
*/
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {
@synchronized(self) {
self.dataTask = nil;
//发送图片下载完成的通知
dispatch_async(dispatch_get_main_queue(), ^{
[[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadStopNotification object:self];
if (!error) {
[[NSNotificationCenter defaultCenter] postNotificationName:SDWebImageDownloadFinishNotification object:self];
}
});
}
if (error) {
[self callCompletionBlocksWithError:error];
} else {
if ([self callbacksForKey:kCompletedCallbackKey].count > 0) {
/**
* If you specified to use `NSURLCache`, then the response you get here is what you need.
* if you specified to only use cached data via `SDWebImageDownloaderIgnoreCachedResponse`,
* the response data will be nil.
* So we don't need to check the cache option here, since the system will obey the cache option
*/
if (self.imageData) {
UIImage *image = [UIImage sd_imageWithData:self.imageData];
//获取url对应的缓存Key
NSString *key = [[SDWebImageManager sharedManager] cacheKeyForURL:self.request.URL];
image = [self scaledImageForKey:key image:image];
// Do not force decoding animated GIFs
if (!image.images) {
//是否加压缩图片数据
if (self.shouldDecompressImages) {
//如果设置了SDWebImageDownloaderScaleDownLargeImages。则返回处理过的图片
if (self.options & SDWebImageDownloaderScaleDownLargeImages) {
#if SD_UIKIT || SD_WATCH
image = [UIImage decodedAndScaledDownImageWithImage:image];
[self.imageData setData:UIImagePNGRepresentation(image)];
#endif
} else {
image = [UIImage decodedImageWithImage:image];
}
}
}
//构建回调Block
if (CGSizeEqualToSize(image.size, CGSizeZero)) {
[self callCompletionBlocksWithError:[NSError errorWithDomain:SDWebImageErrorDomain code:0 userInfo:@{NSLocalizedDescriptionKey : @"Downloaded image has 0 pixels"}]];
} else {
[self callCompletionBlocksWithImage:image imageData:self.imageData error:nil finished:YES];
}
} else {
[self callCompletionBlocksWithError:[NSError errorWithDomain:SDWebImageErrorDomain code:0 userInfo:@{NSLocalizedDescriptionKey : @"Image data is nil"}]];
}
}
}
[self done];
}
/*
验证HTTPS的证书
*/
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition disposition, NSURLCredential *credential))completionHandler {
NSURLSessionAuthChallengeDisposition disposition = NSURLSessionAuthChallengePerformDefaultHandling;
__block NSURLCredential *credential = nil;
//使用可信任证书机构的证书
if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust]) {
//如果SDWebImageDownloaderAllowInvalidSSLCertificates属性设置了，则不验证SSL证书。直接信任
if (!(self.options & SDWebImageDownloaderAllowInvalidSSLCertificates)) {
disposition = NSURLSessionAuthChallengePerformDefaultHandling;
} else {
credential = [NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust];
disposition = NSURLSessionAuthChallengeUseCredential;
}
} else {
//使用自己生成的证书
if (challenge.previousFailureCount == 0) {
if (self.credential) {
credential = self.credential;
disposition = NSURLSessionAuthChallengeUseCredential;
} else {
disposition = NSURLSessionAuthChallengeCancelAuthenticationChallenge;
}
} else {
disposition = NSURLSessionAuthChallengeCancelAuthenticationChallenge;
}
}
//验证证书
if (completionHandler) {
completionHandler(disposition, credential);
}
}
#pragma mark Helper methods
#if SD_UIKIT || SD_WATCH
/**
把整数转换为对应的枚举值
@param value 整数值
@return 枚举值
*/
+ (UIImageOrientation)orientationFromPropertyValue:(NSInteger)value {
switch (value) {
case 1:
return UIImageOrientationUp;
case 3:
return UIImageOrientationDown;
case 8:
return UIImageOrientationLeft;
case 6:
return UIImageOrientationRight;
case 2:
return UIImageOrientationUpMirrored;
case 4:
return UIImageOrientationDownMirrored;
case 5:
return UIImageOrientationLeftMirrored;
case 7:
return UIImageOrientationRightMirrored;
default:
return UIImageOrientationUp;
}
}
#endif
/**
* 通过image对象获取对应scale模式下的图像
*/
- (nullable UIImage *)scaledImageForKey:(nullable NSString *)key image:(nullable UIImage *)image {
return SDScaledImageForKey(key, image);
}
- (BOOL)shouldContinueWhenAppEntersBackground {
return self.options & SDWebImageDownloaderContinueInBackground;
}
- (void)callCompletionBlocksWithError:(nullable NSError *)error {
[self callCompletionBlocksWithImage:nil imageData:nil error:error finished:YES];
}
/**
处理回调
@param image UIImage数据
@param imageData Image的data数据
@param error 错误
@param finished 是否完成的标记位
*/
- (void)callCompletionBlocksWithImage:(nullable UIImage *)image
imageData:(nullable NSData *)imageData
error:(nullable NSError *)error
finished:(BOOL)finished {
//获取key对应的回调Block数组
NSArray *completionBlocks = [self callbacksForKey:kCompletedCallbackKey];
dispatch_main_async_safe(^{
//调用回调
for (SDWebImageDownloaderCompletedBlock completedBlock in completionBlocks) {
completedBlock(image, imageData, error, finished);
}
});
}
@end