Question

我想从Background file transfer运行Background audio agent，但我在前台应用中运行正确的示例代码时出错。

以下是示例：

string transferFileName = @"http://www.reggaeavenue.com/MP3/leave%20short.mp3";
Uri transferUri = new Uri(Uri.EscapeUriString(transferFileName), UriKind.RelativeOrAbsolute);

BackgroundTransferRequest transferRequest = new BackgroundTransferRequest(transferUri);

transferRequest.Method = "GET";

string downloadFile = "result.mp3";
Uri downloadUri = new Uri("shared/transfers/" + downloadFile, UriKind.RelativeOrAbsolute);
transferRequest.DownloadLocation = downloadUri;

transferRequest.Tag = downloadFile;

transferRequest.TransferPreferences = TransferPreferences.AllowCellularAndBattery;

try
{
   BackgroundTransferService.Add(transferRequest);
}
catch (InvalidOperationException ex)
{
     MessageBox.Show("Unable to add background transfer request. " + ex.Message);
}
catch (Exception)
{
     MessageBox.Show("Unable to add background transfer request.");
}

在将transferRequest添加到BackgroundTransferService的行上，我收到错误：

System.InvalidOperationException: Operation is not valid due to the current state of the object.
   at Microsoft.Phone.BackgroundTransfer.BackgroundTransferRequest.SubmitHelper()
   at Microsoft.Phone.BackgroundTransfer.BackgroundTransferRequest.Submit()
   at Microsoft.Phone.BackgroundTransfer.BackgroundTransferService.Add(BackgroundTransferRequest request)
   at Project.AudioPlaybackAgent.AudioPlayer.CreateBackgroundTransfer()

那么可以从后台代理运行transferm吗？我怎样才能解决这个问题？感谢

Answer 1

根据MSDN，后台代理不支持某些API（包括后台传输）。即使您设法做某些事情，您的应用也可能无法通过认证测试。

为什么不在主UI中下载文件或直接从Web源播放文件？

是否可以从后台音频代理运行后台传输？

1 个答案: