Question

我是iOS开发的新手，我想知道是否可以下载多个图像取决于json配置（也可以从Internet下载）。

我了解到，我需要使用：

URLSession(configuration: config, delegate: JsonSessionDelegate.shared, delegateQueue: nil)

但这是问题所在。我需要更新我的应用程序，例如每5个小时使用新配置和新图像。该配置是与每个映像相同的单独REST GET调用。

是否有可能在后台获取json并依靠json单独获取所有图像，将其保存到内存中，并在重新启动应用程序时显示它们？

这是我的代码，AppDelegate：

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {            
        UIApplication.shared.setMinimumBackgroundFetchInterval(UIApplicationBackgroundFetchIntervalMinimum)  
        return true
    }

    func application(_ application: UIApplication, performFetchWithCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {
        let config = URLSessionConfiguration.background(withIdentifier: "background")
        let session = URLSession(configuration: config, delegate: JsonSessionDelegate.shared, delegateQueue: nil)

        let task = session.downloadTask(with: getJsonUrl())
        task.resume()
    }

JsonSessionDelegate.swift：

    static var shared = JsonSessionDelegate()

    func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
        guard let data = try? Data(contentsOf: location) else { return }
        let json = try? JSONSerialization.jsonObject(with: data, options: .mutableContainers) as! [String: Any]

        for (_, id) in json! {
            let config = URLSessionConfiguration.background(withIdentifier: "bg2 \(id)")
            let session = URLSession(configuration: config, delegate: ImageDelegate.shared, delegateQueue: nil)

            let task = session.downloadTask(with: getImageUrl(id: id))
            task.resume()
        }
    }

最后是ImageDelegate：

    static var shared = ImageDelegate()

    func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
        let data = try? Data(contentsOf: location)
        ...
        if allImagesLoaded() {
            saveImages()
        }
    }

当应用未通过REST API运行时，如何分别下载多个图像？

0 个答案: