在后台下载文件和URLSessionDownloadTask

Question

我刚刚将后台下载添加到我的DownloadManager课程中，但我现在有一个问题！例如，我只是添加一个要下载的文件，在表格视图中我有一些值，如：progress，total bytes written等。当我按下主页按钮时，下载将在后台继续，并将完成但处理停在那里！而不是继续100％进程，或更改下载的文件大小。

下载任务方法：

func urlSession(_ session: URLSession,
                downloadTask: URLSessionDownloadTask,
                didWriteData bytesWritten: Int64,
                totalBytesWritten: Int64,
                totalBytesExpectedToWrite: Int64){


DispatchQueue.main.async(execute: {() -> Void in

    let db:Double = round(Double(totalBytesExpectedToWrite) / 10000)/100

    //Added by me
    let dbWritten:Double = round(Double(totalBytesWritten) / 10000)/100

    self.fileSize = (NSString(format:"%.2f MB of %.2f MB", dbWritten,db)) as String

    self.downloadProgress = Double(totalBytesWritten) / Double(totalBytesExpectedToWrite)
    self.downloadProgressTxt = "\(String(Int(Double(self.downloadProgress*100)))) %";
    self.delegate.updateProgress()

})

}

开始下载功能：

  func startDownload(){

        let defConfigObject = URLSessionConfiguration.background(withIdentifier: "com.App.backgoundSession")

        let defaultSession = URLSession(configuration: defConfigObject, delegate: self, delegateQueue: OperationQueue())
        downloadTask = defaultSession.downloadTask(with: fileUrl)
        downloadTask.resume()
        downloadStatus = "Downloading"
        isDownloading = true
        delegate.updateProgress()
    }

在app delegate：

 func application(_ application: UIApplication, handleEventsForBackgroundURLSession identifier: String, completionHandler: @escaping () -> Void) {
        debugPrint("handleEventsForBackgroundURLSession: \(identifier)")
        completionHandler()
    }

如何在后台更新func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask方法？

我在功能中启用了后台模式：