(Delphi ActiveX) Download File (Stream to Local Filesystem)

This example demonstrates how to download the content of a file from Google Drive. The file is streamed to the local filesystem.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Integer;
gAuth: TChilkatAuthGoogle;
rest: TChilkatRest;
bAutoReconnect: Integer;
gdCache: TChilkatCache;
fileId: WideString;
sbPath: TChilkatStringBuilder;
fileStream: TChilkatStream;
jsonResponse: WideString;

begin
success := 1;

// It requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// This example uses a previously obtained access token having permission for the 
// Google Drive scope.

gAuth := TChilkatAuthGoogle.Create(Self);
gAuth.AccessToken := 'GOOGLE_DRIVE_ACCESS_TOKEN';

rest := TChilkatRest.Create(Self);

// Connect using TLS.
// A single REST object, once connected, can be used for many Google Drive REST API calls.
// The auto-reconnect indicates that if the already-established HTTPS connection is closed,
// then it will be automatically re-established as needed.
bAutoReconnect := 1;
success := rest.Connect('www.googleapis.com',443,1,bAutoReconnect);

// Provide the authentication credentials (i.e. the access token)
rest.SetAuthGoogle(gAuth.ControlInterface);

// ------------------------------------------------------------------------------
// To download a file, we must know the file ID.
// In a previous example (see Build Local Metadata Cache
// we built a local cache to make it easy to lookup file IDs given a file path.
// Let's say we want to download "testFolder/abc/123/penguins.jpg".
// First we lookup the fileId in the cache.  With the fileId, we can download the file.
gdCache := TChilkatCache.Create(Self);
gdCache.Level := 0;
gdCache.AddRoot('C:/ckCache/googleDrive');

fileId := gdCache.FetchText('testFolder/abc/123/penguins.jpg');
if (gdCache.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add('Filepath not found in cache.');
    Exit;
  end;

// We need to send a GET request like this:
// GET https://www.googleapis.com/drive/v3/files/fileId?alt=media
// The fileId is part of the path.
sbPath := TChilkatStringBuilder.Create(Self);
sbPath.Append('/drive/v3/files/');
sbPath.Append(fileId);
rest.AddQueryParam('alt','media');

// Create a stream object with a SinkFile set to the path where the downloaded file will go.
fileStream := TChilkatStream.Create(Self);
fileStream.SinkFile := 'qa_output/penguins.jpg';
// Indicate that the response body should stream directly to fileStream,
// but only if the response status is 200.  
rest.SetResponseBodyStream(200,1,fileStream.ControlInterface);

// Download the file, streaming the content to the SinkFile.
jsonResponse := rest.FullRequestNoBody('GET',sbPath.GetAsString());
if (rest.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(rest.LastErrorText);
    Exit;
  end;

// A successful response will have a status code equal to 200.
if (rest.ResponseStatusCode <> 200) then
  begin
    Memo1.Lines.Add('response status code = ' + IntToStr(rest.ResponseStatusCode));
    Memo1.Lines.Add('response status text = ' + rest.ResponseStatusText);
    Memo1.Lines.Add('response header: ' + rest.ResponseHeader);
    Exit;
  end;

Memo1.Lines.Add('File downloaded.');
end;