如何在 WPF 中从 Google 驱动器下载文件 - 已安装的应用程序

Question

我正在开发 WPF 应用程序，在此我正在实现具有上传和下载功能的 Google Drive API。上传工作正常，但我在下载文档时遇到问题。我在https://developers.google.com/drive/web/manage-downloads查看了谷歌文档中的代码

 public static System.IO.Stream DownloadFile(IAuthenticator authenticator, File file) 
 {
   if (!String.IsNullOrEmpty(file.DownloadUrl)) 
   {
     try {
       HttpWebRequest request = (HttpWebRequest)WebRequest.Create(new Uri(file.DownloadUrl));
       authenticator.ApplyAuthenticationToRequest(request);
       HttpWebResponse response = (HttpWebResponse) request.GetResponse();
       if (response.StatusCode == HttpStatusCode.OK) 
       {
          return response.GetResponseStream();
       }
       else
       {
          Console.WriteLine("An error occurred: " + response.StatusDescription);
          return null;
       }
    }
    catch (Exception e) 
    {
      Console.WriteLine("An error occurred: " + e.Message);
      return null;
    }
  }
  else
  {
    // The file doesn't have any content stored on Drive.
    return null;
  }

}

但是根据这个文件 “https://code.google.com/p/google-api-dotnet-client/source/browse/Src/GoogleApis/Apis/Authentication/IAuthenticator.cs?r=e6585033994bfb3a24d4c140db834cb14b9738b2” 它显示“不再支持 IAuthenticator”，因此上述代码不起作用。

我尝试使用 UserCredential，但它抛出“远程服务器返回错误：(401) 未授权。”。

所以请在 WPF 应用程序中提供相同的代码，或者我如何从 Google 驱动器下载任何类型的文件。

Answer 1

根据文档，您需要下载新的 Google.Apis.Auth nuget 包。之后按照以下步骤操作

• 访问 Google API 控制台
• 如果这是您第一次，请点击“创建项目...”
• 否则，请点击左上角“Google APIs”徽标下方的下拉菜单，然后点击“其他项目”下的“创建...”
• 点击“API 访问”，然后点击“创建 OAuth 2.0 客户端 ID...”。
• 输入产品名称并点击“下一步”。
• 选择“已安装的应用程序”并单击“创建客户端 ID”。
• 在新创建的“已安装应用程序的客户端 ID”中，将客户端 ID 和客户端机密复制到 AdSenseSample.cs 文件中。
• 为您的项目激活 Drive API。

参考Google APIs Client Library for .NET

完成这些步骤后，您可以使用以下代码下载文件

private async Task Run()
    {
        GoogleWebAuthorizationBroker.Folder = "Drive.Sample";
        UserCredential credential;
        using (var stream = new System.IO.FileStream("client_secrets.json",
            System.IO.FileMode.Open, System.IO.FileAccess.Read))
        {
            credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(
                GoogleClientSecrets.Load(stream).Secrets, Scopes, "user", CancellationToken.None);
        }

        // Create the service.
        var service = new DriveService(new BaseClientService.Initializer()
        {
            HttpClientInitializer = credential,
            ApplicationName = "Drive API Sample",
        });

        await UploadFileAsync(service);

        // uploaded succeeded
        Console.WriteLine("\"{0}\" was uploaded successfully", uploadedFile.Title);
        await DownloadFile(service, uploadedFile.DownloadUrl);
        await DeleteFile(service, uploadedFile);
    }


    private async Task DownloadFile(DriveService service, string url)
    {
        var downloader = new MediaDownloader(service);
        downloader.ChunkSize = DownloadChunkSize;
        // add a delegate for the progress changed event for writing to console on changes
        downloader.ProgressChanged += Download_ProgressChanged;

        // figure out the right file type base on UploadFileName extension
        var lastDot = UploadFileName.LastIndexOf('.');
        var fileName = DownloadDirectoryName + @"\Download" +
            (lastDot != -1 ? "." + UploadFileName.Substring(lastDot + 1) : "");
        using (var fileStream = new System.IO.FileStream(fileName,
            System.IO.FileMode.Create, System.IO.FileAccess.Write))
        {
            var progress = await downloader.DownloadAsync(url, fileStream);
            if (progress.Status == DownloadStatus.Completed)
            {
                Console.WriteLine(fileName + " was downloaded successfully");
            }
            else
            {
                Console.WriteLine("Download {0} was interpreted in the middle. Only {1} were downloaded. ",
                    fileName, progress.BytesDownloaded);
            }
        }
    }

您可以下载sample application 用于 google drive api。