StorageFolder 没有通过异步获取文件夹取回任何数据

Question

我遵循了一个关于如何访问使用文件夹选择器选择的文件夹的 Microsoft 示例。完成此操作后，我想获取所选顶级文件夹中子文件夹的所有路径。但是我没有得到任何结果。

代码：

var folderPicker = new Windows.Storage.Pickers.FolderPicker();
folderPicker.SuggestedStartLocation = Windows.Storage.Pickers.PickerLocationId.Desktop;
folderPicker.FileTypeFilter.Add("*");
folderPicker.ViewMode = Windows.Storage.Pickers.PickerViewMode.List;
Windows.Storage.StorageFolder folder = await folderPicker.PickSingleFolderAsync();

if (folder != null)
{
    Windows.Storage.AccessCache.StorageApplicationPermissions.FutureAccessList.AddOrReplace("GameFilesToken", folder);
    System.Diagnostics.Debug.WriteLine(folder.Path);

    await FileManagementHelper.getFolders(folder.Path);
}

public static async Task<Queue<string>> getFolders(String TopLevel)
{
    var Folder = await Windows.Storage.AccessCache.StorageApplicationPermissions.FutureAccessList.GetFolderAsync("GameFilesToken");

    var queryResults = Folder.CreateFolderQuery();
    var folderList = await queryResults.GetFoldersAsync();

    return new Queue<string>();
}

QueryResults 允许我访问一个文件夹，即我最初使用的文件夹。 FolderList 什么也没给我。

Answer 1

FolderList 什么也没给我。

你得到的folderList 代码 sn-p 可以很好地工作，如果所选文件夹有子文件夹，folderList 对象确实有值。请更新您的getfolders 方法以通过代码检查folderList，如下所示：

   var Folder = await Windows.Storage.AccessCache.StorageApplicationPermissions.FutureAccessList.GetFolderAsync("GameFilesToken");
   var queryResults = Folder.CreateFolderQuery();
   var folderList = await queryResults.GetFoldersAsync();
   foreach (StorageFolder folder in  folderList )
   {
       Debug.WriteLine(folder.Path); 
   }

我想获取所选顶级文件夹中子文件夹的所有路径。但是我没有得到任何结果。

实际上，您可以使用StorageFolder.GetFoldersAsync() 方法获取所选顶层文件夹对象的所有子文件夹，如果要全部列出，则无需使用CreateFolderQuery() 方法。代码如下：

private async void btngetfolder_Click(object sender, RoutedEventArgs e)
{
    var folderPicker = new Windows.Storage.Pickers.FolderPicker();
    folderPicker.SuggestedStartLocation = Windows.Storage.Pickers.PickerLocationId.Desktop;
    folderPicker.FileTypeFilter.Add("*");
    folderPicker.ViewMode = Windows.Storage.Pickers.PickerViewMode.List;
    Windows.Storage.StorageFolder folder = await folderPicker.PickSingleFolderAsync();

    if (folder != null)
    {
        IReadOnlyList<StorageFolder> folderList = await folder.GetFoldersAsync();
        foreach (StorageFolder subfolder in folderList)
        {
            Debug.WriteLine("subfolder path:" + subfolder.Path);
        } 
    }
}

更多详情请参考FolderEnumeration官方示例。

更新： 如果要获取所有子文件夹包括后代子文件夹，则需要将QueryOptions.FolderDepth 设置为深度。代码如下：

 var Folder = await Windows.Storage.AccessCache.StorageApplicationPermissions.FutureAccessList.GetFolderAsync("GameFilesToken");
 QueryOptions options = new QueryOptions();
 options.FolderDepth = FolderDepth.Deep;
 var queryResults = Folder.CreateFolderQueryWithOptions(options);    
 var folderList = await queryResults.GetFoldersAsync();

 foreach (StorageFolder folder in  folderList )
 {
     Debug.WriteLine(folder.Path); 
 }