Xamarin表单-在ScanFilesToFolderAsync上抛出TaskCanceledException [英] Xamarin Form - TaskCanceledException thrown on ScanFilesToFolderAsync

问题描述

在我的UWP应用程序中，我正在使用扫描功能.在此应用程序中，用户可以通过选择平板扫描仪或自动进纸器来通过扫描仪扫描文档.现在的问题是，当我尝试对其进行扫描时，出现了一个任务被取消的例外情况.

in my UWP application i am working on scan functionality. in this application user can scan the document through scanner by selecting flatbed or auto feeder.Now problem is when i am trying to scan it gives the en exception a Task was canceled.

请帮助.

先谢谢了. :)

祝你有美好的一天...:)

have a great day... :)

private async void Btnscan_Click(object sender, RoutedEventArgs e)
    {

        FolderPicker folderPicker = new FolderPicker();
        folderPicker.SuggestedStartLocation = PickerLocationId.DocumentsLibrary;
        folderPicker.FileTypeFilter.Add("*");

        StorageFolder folder = await folderPicker.PickSingleFolderAsync();
//set the destination folder name for scan images.


        DeviceInformationDisplay selectedScanner = CmbScannerList.SelectedItem as DeviceInformationDisplay; // here i got the selected scanner.

        // scanner id is := "\\\\?\\ROOT#IMAGE#0000#{6bdd1fc6-810f-11d0-bec7-08002be2092f}"

        ScanToFolder(selectedScanner.id, folder);


    }

功能扫描到"文件夹

 public async void ScanToFolder(string deviceId, StorageFolder folder)
    {
        try
        {
 cancellationToken = new CancellationTokenSource();

            ImageScanner myScanner = await ImageScanner.FromIdAsync(deviceId);

            if (myScanner.IsScanSourceSupported(ImageScannerScanSource.Flatbed))
            {
                var result = await myScanner.ScanFilesToFolderAsync(ImageScannerScanSource.Flatbed, folder).AsTask(cancellationToken.Token); // through an exception(A Task Was Canceled):(
Utils.DisplayImageAndScanCompleteMessage(result.ScannedFiles, DisplayImage);

            }

        }

        catch (Exception ex)
        {
            // here i got the exception.
        }

    }

已更新:

现在我将DeviceClass设置为ALL.

Now i am set the DeviceClass to ALL.

   private void StartWatcher()
    {
        resultCollection.Clear();
        DeviceWatcher deviceWatcher;

        deviceWatcher = DeviceInformation.CreateWatcher(DeviceClass.All); // set Image scanner to all. 
       deviceWatcherHelper.StartWatcher(deviceWatcher);
  }

在扫描仪列表中运行项目后，我得到了所有连接的设备，在其中获得了我的扫描仪名称，这是:当我尝试传递此名称时，它在imagescanner System.Exception中给出了错误:'HRESULT的异常:0x80210015'表示未找到设备. 现在，我全都使用ImageScanner了，而我在扫描仪列表中什么也没得到.

After run the project in scanner list i got the all connected devices in which i got my scanner name This : when i am trying to pass this name it gives error in imagescanner System.Exception: 'Exception from HRESULT: 0x80210015' means device not found. Now i am chnage all to ImageScanner i got nothing in scanner list.

在扫描仪HP应用程序中，我得到了这个名称.和IT Scan Well :(在扫描仪列表中，我的应用程序中没有此名称.:(

and in scanner HP application i got this name. and IT Scan Well :( in scanner list i don't got this name in my application. :(

在我的电脑设置->设备->扫描仪和打印机上，我得到了这些名称.

on my pc setting -> devices -> scanner and printers i got those name.

推荐答案

将问题的解决方法重写为答案.我在机器上正确运行的代码上进行了测试，并认为该问题很可能是驱动程序问题.这已由OP确认，重新安装驱动程序有助于再次进行扫描.

Rewriting the resolution of the problem as an answer. I tested the code on my machine where it behaved correctly and argued the problem is most likely a driver issue. This has been confirmed by the OP and reinstall of the driver helped make the scanning work again.

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