(Xojo Plugin) Facebook OAuth2 Access Token

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

Chilkat Xojo Plugin Download Xojo Plugin for Windows, Linux, Mac OS X, and ARM, ARM64

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

Dim oauth2 As New Chilkat.OAuth2
Dim success As Boolean

// 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 these with actual values.
oauth2.ClientId = "FACEBOOK-CLIENT-ID"
oauth2.ClientSecret = "FACEBOOK-CLIENT-SECRET"

// 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,publish_actions"

oauth2.CodeChallenge = True
oauth2.CodeChallengeMethod = "S256"

// Begin the OAuth2 three-legged flow.  This returns a URL that should be loaded in a browser.
Dim url As String
url = oauth2.StartAuth()
If (oauth2.LastMethodSuccess <> True) Then
    System.DebugLog(oauth2.LastErrorText)
    Return
End If

// At this point, your application should load the URL in a browser.
// For example, 
// in C#:  System.Diagnostics.Process.Start(url);
// in Java: Desktop.getDesktop().browse(new URI(url));
// in VBScript: Set wsh=WScript.CreateObject("WScript.Shell")
//              wsh.Run url
// in Xojo: ShowURL(url)  (see http://docs.xojo.com/index.php/ShowURL)
// in Dataflex: Runprogram Background "c:\Program Files\Internet Explorer\iexplore.exe" sUrl        
// The Facebook account owner would interactively accept or deny the authorization request.

// Add the code to load the url in a web browser here...
// Add the code to load the url in a web browser here...
// Add the code to load the url in a web browser here...

// Now wait for the authorization.
// We'll wait for a max of 30 seconds.
Dim numMsWaited As Int32
numMsWaited = 0
While (numMsWaited < 30000) And (oauth2.AuthFlowState < 3)
    oauth2.SleepMs 100
    numMsWaited = numMsWaited + 100
Wend

// If there was no response from the browser within 30 seconds, then 
// the AuthFlowState will be equal to 1 or 2.
// 1: Waiting for Redirect. The OAuth2 background thread is waiting to receive the redirect HTTP request from the browser.
// 2: Waiting for Final Response. The OAuth2 background thread is waiting for the final access token response.
// In that case, cancel the background task started in the call to StartAuth.
If (oauth2.AuthFlowState < 3) Then
    success = oauth2.Cancel()
    System.DebugLog("No response from the browser!")
    Return
End If

// Check the AuthFlowState to see if authorization was granted, denied, or if some error occurred
// The possible AuthFlowState values are:
// 3: Completed with Success. The OAuth2 flow has completed, the background thread exited, and the successful JSON response is available in AccessTokenResponse property.
// 4: Completed with Access Denied. The OAuth2 flow has completed, the background thread exited, and the error JSON is available in AccessTokenResponse property.
// 5: Failed Prior to Completion. The OAuth2 flow failed to complete, the background thread exited, and the error information is available in the FailureInfo property.
If (oauth2.AuthFlowState = 5) Then
    System.DebugLog("OAuth2 failed to complete.")
    System.DebugLog(oauth2.FailureInfo)
    Return
End If

If (oauth2.AuthFlowState = 4) Then
    System.DebugLog("OAuth2 authorization was denied.")
    System.DebugLog(oauth2.AccessTokenResponse)
    Return
End If

If (oauth2.AuthFlowState <> 3) Then
    System.DebugLog("Unexpected AuthFlowState:" + Str(oauth2.AuthFlowState))
    Return
End If

System.DebugLog("OAuth2 authorization granted!")
System.DebugLog("Access Token = " + oauth2.AccessToken)