Delphi ActiveX

Facebook OAuth2 Access Token

See more Facebook Examples

Demonstrates how to get a Facebook OAuth2 access token from a desktop application or script. Delphi ActiveX

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;
oauth2: TChilkatOAuth2;
url: WideString;
numMsWaited: Integer;

begin
success := 0;

// To further clarify, see OAuth 2.0 Authorization Flow

oauth2 := TChilkatOAuth2.Create(Self);

// This should match the Site URL configured for your Facebook APP, such as "http://localhost:3017/"
oauth2.ListenPort := 3017;

oauth2.AuthorizationEndpoint := 'https://www.facebook.com/dialog/oauth';
oauth2.TokenEndpoint := 'https://graph.facebook.com/oauth/access_token';

// Replace this with your actual App ID
oauth2.ClientId := 'APP_ID';

// Set the Scope to a comma-separated list of permissions the app wishes to request.
// See https://developers.facebook.com/docs/facebook-login/permissions/ for a full list of permissions.
oauth2.Scope := 'public_profile,user_friends,email,user_posts,user_likes,user_photos';

// This is for Require Proof Key for Code Exchange (PKCE)
// See OAuth2 PKCE Explained
oauth2.CodeChallenge := 1;
oauth2.CodeChallengeMethod := 'S256';

// Begin the OAuth2 Authorization code flow.  This returns a URL that should be loaded in a browser.
url := oauth2.StartAuth();
if (oauth2.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(oauth2.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('url = ' + url);

// Launch the default browser on the system and navigate to the url.
// The LaunchBrowser method was added in Chilkat v10.1.2.
success := oauth2.LaunchBrowser(url);
if (success = 0) then
  begin
    Memo1.Lines.Add(oauth2.LastErrorText);
    Exit;
  end;

// Wait for the user to approve or deny authorization in the browser.
numMsWaited := 0;
while (numMsWaited < 90000) and (oauth2.AuthFlowState < 3) do
  begin
    oauth2.SleepMs(100);
    numMsWaited := numMsWaited + 100;
  end;

// If the browser does not respond within the specified time, AuthFlowState will be:
// 
// 1: Waiting for Redirect – The OAuth2 background thread is waiting for the browser's redirect request.
// 2: Waiting for Final Response – The thread is awaiting the final access token response.
// In either case, cancel the background task initiated by StartAuth.

if (oauth2.AuthFlowState < 3) then
  begin
    oauth2.Cancel();
    Memo1.Lines.Add('No response from the browser!');
    Exit;
  end;

// Check AuthFlowState to determine if authorization was granted, denied, or failed:
// 
// 3: Success – OAuth2 flow completed, the background thread exited, and the successful response is in AccessTokenResponse.
// 4: Access Denied – OAuth2 flow completed, the background thread exited, and the error response is in AccessTokenResponse.
// 5: Failure – OAuth2 flow failed before completion, the background thread exited, and error details are in FailureInfo.

if (oauth2.AuthFlowState = 5) then
  begin
    Memo1.Lines.Add('OAuth2 failed to complete.');
    Memo1.Lines.Add(oauth2.FailureInfo);
    Exit;
  end;

if (oauth2.AuthFlowState = 4) then
  begin
    Memo1.Lines.Add('OAuth2 authorization was denied.');
    Memo1.Lines.Add(oauth2.AccessTokenResponse);
    Exit;
  end;

if (oauth2.AuthFlowState <> 3) then
  begin
    Memo1.Lines.Add('Unexpected AuthFlowState:' + IntToStr(oauth2.AuthFlowState));
    Exit;
  end;

Memo1.Lines.Add('OAuth2 authorization granted!');
Memo1.Lines.Add('Access Token = ' + oauth2.AccessToken);
end;