Question

我有500多个图像链接，我想下载这些图像并在应用程序启动时本地存储在应用程序文档目录中。我正在使用Almofire下载，但出现了类似的错误 “ URLSession任务已取消”，并请求超时

func downloadAllImages(images:[String: String], retryCount: Int = 0,completion: @escaping((Bool)->Void)){
        var success: Bool = true
        var failedImages = [String: String]()
        for (localName, severPath) in images {
            self.dispatchGroup.enter()
            
            let destination: DownloadRequest.Destination = { _, _ in
                let documentsURL = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
                let fileURL = documentsURL.appendingPathComponent(localName)
                return (fileURL, [.removePreviousFile, .createIntermediateDirectories])
            }
           
            
            let path = severPath.replacingOccurrences(of: "\\", with: "/").addingPercentEncoding(withAllowedCharacters: .urlQueryAllowed) ?? ""
        
            //AF.sessionConfiguration.httpShouldSetCookies = false
            AF.download(path, to: destination).response { response in
                switch response.result {
                case .success(_):
                    break
                case .failure(let error):
                    if response.response?.statusCode != 404 {
                        success = false
                        failedImages[localName] = path
                        print("Image Download Error = \(error.localizedDescription)")
                    }
                    break
                }
                debugPrint(response)
                self.dispatchGroup.leave()
            }
        }
        dispatchGroup.notify(queue: .main) {
            //retry If some Images failed to download
            if failedImages.isEmpty || retryCount >= self.maximumRetryCount {
                completion(success)
            }else {
                self.downloadAllImages(images: failedImages, retryCount: retryCount + 1) { (success) in
                    completion(success)
                }
            }
        }
    }

images词典包含 localName作为键 serverPath作为值

Answer 1

AFImageDownloaders的活动下载有限制，我相信更改maximumActiveDownloads或您的API中的类似内容都可以解决此问题。新的下载只会取消以前的下载。但是最好分块下载它们。

例如，这个用于ImageDownloader

 public init(session: Session,
                downloadPrioritization: DownloadPrioritization = .fifo,
                maximumActiveDownloads: Int = 4,
                imageCache: ImageRequestCache? = AutoPurgingImageCache()) {
        precondition(!session.startRequestsImmediately, "Session must set `startRequestsImmediately` to `false`.")

        self.session = session
        self.downloadPrioritization = downloadPrioritization
        self.maximumActiveDownloads = maximumActiveDownloads
        self.imageCache = imageCache
    }

UPD：限制不是自动对焦，而是URLSession。一个AF下载器使用一个URLSession。您必须通过自定义URLSessionConfigurations来处理更多活动下载HTTPMaximumConnectionsPerHost。并通过AF Session类

Almofire多张图片下载并保存到本地

1 个答案: