c# - 在 Windows Phone 中使用 Background Downloader 进行多次下载

Question

我可以通过这段代码将文件下载到SD卡中>

    DownloadOperation downloadOperation;
    CancellationTokenSource cancellationToken;

    BackgroundDownloader backgroundDownloader = new BackgroundDownloader();
    async private void ButtonDownload_Click(object sender, RoutedEventArgs e)
    {
        StorageFolder externalDevices = Windows.Storage.KnownFolders.RemovableDevices;
        StorageFolder sdCard = (await externalDevices.GetFoldersAsync()).FirstOrDefault();
        if (sdCard != null)
        {
            StorageFile file = await sdCard.CreateFileAsync("Downloads\\d460809d2cef1.pdf", CreationCollisionOption.GenerateUniqueName);
            downloadOperation = backgroundDownloader.CreateDownload(new Uri("http://dowmain.com/uploads/d460809d2cef1.pdf"), file);
            CancellationTokenSource cts = new CancellationTokenSource();
            Progress<DownloadOperation> progress = new Progress<DownloadOperation>(progressChanged);
            cancellationToken = new CancellationTokenSource();
            try
            {
                await downloadOperation.StartAsync().AsTask(cancellationToken.Token, progress);
            }
            catch (TaskCanceledException)
            {
                TextBlockStatus.Text = "Download canceled.";
                downloadOperation.ResultFile.DeleteAsync();
                downloadOperation = null;
            }
        }
    }

    private void progressChanged(DownloadOperation downloadOperation)
    {
        int progress = (int)(100 * ((double)downloadOperation.Progress.BytesReceived / (double)downloadOperation.Progress.TotalBytesToReceive));
        TextBlockProgress.Text = String.Format("{0} of {1} kb. downloaded - %{2} complete.", downloadOperation.Progress.BytesReceived / 1024, downloadOperation.Progress.TotalBytesToReceive / 1024, progress);
        ProgressBarDownload.Value = progress;
        switch (downloadOperation.Progress.Status)
        {
            case BackgroundTransferStatus.Running:
                {
                    TextBlockStatus.Text = "Downloading...";
                    ButtonPauseResume.Content = "Pause";
                    break;
                }
            case BackgroundTransferStatus.PausedByApplication:
                {
                    TextBlockStatus.Text = "Download paused.";
                    ButtonPauseResume.Content = "Resume";
                    break;
                }
            case BackgroundTransferStatus.PausedCostedNetwork:
                {
                    TextBlockStatus.Text = "Download paused because of metered connection.";
                    ButtonPauseResume.Content = "Resume";
                    break;
                }
            case BackgroundTransferStatus.PausedNoNetwork:
                {
                    TextBlockStatus.Text = "No network detected. Please check your internet connection.";
                    break;
                }
            case BackgroundTransferStatus.Error:
                {
                    TextBlockStatus.Text = "An error occured while downloading.";
                    break;
                }
        }
        if (progress >= 100)
        {
            TextBlockStatus.Text = "Download complete.";
            downloadOperation = null;
        }
    }

我有两个问题:

1. 我想下载多个文件并显示过程，但我不知道该怎么做。你能给我一个解决方案或源代码吗？
2. 我可以访问 SD 卡进行下载，但如何将文件下载到我的手机内存中？

Answer 1

您的文件下载代码工作正常。但是这里不会持续更新状态，

对于您的第二个问题，您可以使用此工具将您的 pdf 文件下载到 Windows Phone 存储中。

  StorageFolder storageFolder = KnownFolders.DocumentsLibrary;

  var file= await storageFolder.CreateFileAsync("fileName", CreationCollisionOption.GenerateUniqueName);

其他的事情将保持不变。 希望这会奏效，