swift3.0 Kingfisher图片库 重点源码分析

概述1. data 根据url这个key存储在 fetchLoads中// A single key may have multiple callbacks. Only download once. func setup(progressBlock: ImageDownloaderProgressBlock?, with completionHandler: ImageDownloader

1. data 根据url这个key存储在 fetchLoads中// A single key may have multiple callbacks. Only download once.    func setup(progressBlock: ImageDownloaderProgressBlock?,with completionHandler: ImageDownloaderCompletionHandler?,for url: URL,options: KingfisherOptionsInfo?,started: ((URLSession,ImageFetchLoad) -> VoID)) {        barrIErQueue.sync(flags: .barrIEr) {            let loadobjectForURL = fetchLoads[url] ?? ImageFetchLoad()            let callbackPair = (progressBlock: progressBlock,completionHandler: completionHandler)                        loadobjectForURL.contents.append((callbackPair,options ?? KingfisherEmptyOptionsInfo))                        //data 根据url这个key存储在 fetchLoads中            fetchLoads[url] = loadobjectForURL                        if let session = session {                started(session,loadobjectForURL)            }        }    }2. 获取每次网络传输过来的数据  func urlSession(_ session: URLSession,dataTask: URLSessionDataTask,dIDReceive data: Data) {        print("Data......\(data)")        guard let downloader = downloadHolder else {            return        }        if let url = dataTask.originalRequest?.url,let fetchLoad = downloader.fetchLoad(for: url) {        1.将获取的数据data放到downloadHolder.fetchLoad (此处的downloader和downloadHolder是同一块内存地址，所以给downloader拼接获取的网络数据，就相当于给downloadHolder拼接数据)中去。               2.downloadHolder为全局变量，以便于后面获取数据完毕后，可以根据url来取data           fetchLoad.responseData.append(data) //存储每次获取的数据       }3. 网络数据获取完毕，进行图片解码，图片缓存到本地    //图片数据加载完毕，进入此回调方法    func urlSession(_ session: URLSession,task: URLSessionTask,dIDCompleteWithError error: Error?) {                guard let url = task.originalRequest?.url else {            retur        }                guard error == nil else {            callCompletionHandlerFailure(error: error!,url: url)            return        }        //数据请求完，在此处完成completionHandler 回调               //在这个函数中，根据url去downloadHolder取image 的data数据，然后解码，存储。         processImage(for: task,url: url)        }

4. data数据处理成image的方法

    //数据请求完，在此处完成completionHandler 回调    //对于每一张根据URL取出来的data，在此做图片的预处理。    //当选择图片的默认处理方式时，var image = imageCache[processor.IDentifIEr]中的    //processor.IDentifIEr = ""处理，具体看IDentifIEr的定义说明    private func processImage(for task: URLSessionTask,url: URL) {        guard let downloader = downloadHolder else {            return        }                // We are on main queue when receiving this.        downloader.processQueue.async {                        guard let fetchLoad = downloader.fetchLoad(for: url) else {                return            }                        self.cleanFetchLoad(for: url)                        let data = fetchLoad.responseData as Data                        // Cache the processed images. So we do not need to re-process the image if using the same processor.            // Key is the IDentifIEr of processor.            var imageCache: [String: Image] = [:]            for content in fetchLoad.contents {                                let options = content.options                let completionHandler = content.callback.completionHandler                let callbackQueue = options.callbackdispatchQueue                                let processor = options.processor                                var image = imageCache[processor.IDentifIEr]                if image == nil {                    image = processor.process(item: .data(data),options: options)                                        // Add the processed image to cache.                     // If `image` is nil,nothing will happen (since the key is not existing before).                    imageCache[processor.IDentifIEr] = image                }                                if let image = image {                                        downloader.delegate?.imageDownloader(downloader,dIDDownload: image,for: url,with: task.response)                                        if options.backgroundDecode {                        let decodedImage = image.kf.decoded(scale: options.scaleFactor)                        callbackQueue.safeAsync { completionHandler?(decodedImage,nil,url,data) }                    } else {                        callbackQueue.safeAsync { completionHandler?(image,data) }                    }                                    } else {                    if let res = task.response as? httpURLResponse,res.statusCode == 304 {                        let notModifIEd = NSError(domain: KingfisherErrorDomain,code: KingfisherError.notModifIEd.rawValue,userInfo: nil)                                                //数据请求完，在此处完成completionHandler 回调                        completionHandler?(nil,notModifIEd,nil)                        continue                    }                                        let badData = NSError(domain: KingfisherErrorDomain,code: KingfisherError.badData.rawValue,userInfo: nil)                    callbackQueue.safeAsync { completionHandler?(nil,badData,nil) }                }            }        }    }}

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