一针见血
SDWebImage使用了NSURLSession下载网络图片。
找网络图片下载代码路线
寻找路线.png
1.UIImageView+WebCache
- (void)sd_setImageWithURL:(nullable NSURL *)url completed:(nullable SDExternalCompletionBlock)completedBlock {
[self sd_setImageWithURL:url placeholderImage:nil options:0 progress:nil completed:completedBlock];
}
2.UIView+WebCache
- (void)sd_internalSetImageWithURL:(nullable NSURL *)url
placeholderImage:(nullable UIImage *)placeholder
options:(SDWebImageOptions)options
context:(nullable SDWebImageContext *)context
setImageBlock:(nullable SDSetImageBlock)setImageBlock
progress:(nullable SDImageLoaderProgressBlock)progressBlock
completed:(nullable SDInternalCompletionBlock)completedBlock；
/******************************************************************/
id <SDWebImageOperation> operation = [manager loadImageWithURL:url options:options context:context progress:combinedProgressBlock completed:^(UIImage *image, NSData *data, NSError *error, SDImageCacheType cacheType, BOOL finished, NSURL *imageURL) {
NSLog(@"image:===%@", image);
NSLog(@"下载完图片的回调...");
3.SDWebImageManager
NSLog(@"调用获取图片的方法...");
[self callCacheProcessForOperation:operation url:url options:options context:context progress:progressBlock completed:completedBlock];
/****************************************************************/
NSLog(@"callDownloadProcessForOperation...");
[self callDownloadProcessForOperation:strongOperation url:url options:options context:context cachedImage:cachedImage cachedData:cachedData cacheType:cacheType progress:progressBlock completed:completedBlock];
/****************************************************************/
NSLog(@"调用SDWebImageDownloader下载图片的方法...");
operation.loaderOperation = [self.imageLoader loadImageWithURL:url options:options context:context progress:progressBlock completed:^(UIImage *downloadedImage, NSData *downloadedData, NSError *error, BOOL finished) {
4.SDWebImageDownloader
- (nullable SDWebImageDownloadToken *)downloadImageWithURL:(nullable NSURL *)url
options:(SDWebImageDownloaderOptions)options
context:(nullable SDWebImageContext *)context
progress:(nullable SDWebImageDownloaderProgressBlock)progressBlock
completed:(nullable SDWebImageDownloaderCompletedBlock)completedBlock {
__weak SDWebImageDownloader *wself = self;
NSLog(@"下载图片...");
return [self addProgressCallback:progressBlock completedBlock:completedBlock forURL:url createCallback:^NSOperation<SDWebImageDownloaderOperation> *{
/****************************************************************/
NSLog(@"调用SDWebImageDownloaderOperation的addHandlersForProgress方法..");
id downloadOperationCancelToken = [operation addHandlersForProgress:progressBlock completed:completedBlock];
5.SDWebImageDownloaderOperation
#pragma mark NSURLSessionDataDelegate
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data {
NSLog(@"%s", __func__);
if (!self.imageData) {
self.imageData = [[NSMutableData alloc] initWithCapacity:self.expectedSize];
}
[self.imageData appendData:data];
在SDWebImageDownloader中创建SDWebImageDownloaderOperation对象的时候将session传递给了SDWebImageDownloaderOperation对象，[self.dataTask resume];的操作是在SDWebImageDownloaderOperation中执行的。
个人疑问：
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data {
NSLog(@"----%s", __func__);
// Identify the operation that runs this task and pass it the delegate method
NSOperation<SDWebImageDownloaderOperation> *dataOperation = [self operationWithTask:dataTask];
if ([dataOperation respondsToSelector:@selector(URLSession:dataTask:didReceiveData:)]) {
[dataOperation URLSession:session dataTask:dataTask didReceiveData:data];
}
}
SDWebImageDownloader中的NSURLSessionTaskDelegate代理方法在SDWebImageDownloaderOperation中是如何能执行的？
本篇文章到这里就结束了，愿大家加班不多工资多，男同胞都有女朋友，女同胞都有男朋友。😊
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