(Visual Basic 6.0) Dropbox: OAuth2 Authorization to Obtain an Access Token

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

This example runs the OAuth 2.0 authorization flow that lets the user sign in to Dropbox and authorize your app.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

' Note: This example requires Chilkat v9.5.0.66 or greater to work properly.

Dim oauth2 As New ChilkatOAuth2
Dim success As Long

' The port should match the Authorized Redirect URL in your Dropbox app, 
' which would look like "http://localhost:3017/"
oauth2.ListenPort = 3017

' IMPORTANT: One of the OAuth2 redirect URIs for your Dropbox app must be
' exactly this string:  http://localhost:3017/

oauth2.AuthorizationEndpoint = "https://www.dropbox.com/oauth2/authorize"
oauth2.TokenEndpoint = "https://api.dropboxapi.com/oauth2/token"

' Replace these with actual values.
oauth2.ClientId = "DROPBOX_APP_KEY"
oauth2.ClientSecret = "DROPBOX_APP_SECRET"
oauth2.CodeChallenge = 0

' Add token_access_type=offline to also get a refresh token in the response
success = oauth2.AddAuthQueryParam("token_access_type","offline")

' 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 <> 1) Then
    Debug.Print oauth2.LastErrorText
    Exit Sub
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 Microsoft 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 Long
numMsWaited = 0
Do While (numMsWaited < 30000) And (oauth2.AuthFlowState < 3)
    oauth2.SleepMs 100
    numMsWaited = numMsWaited + 100
Loop

' 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()
    Debug.Print "No response from the browser!"
    Exit Sub
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
    Debug.Print "OAuth2 failed to complete."
    Debug.Print oauth2.FailureInfo
    Exit Sub
End If

If (oauth2.AuthFlowState = 4) Then
    Debug.Print "OAuth2 authorization was denied."
    Debug.Print oauth2.AccessTokenResponse
    Exit Sub
End If

If (oauth2.AuthFlowState <> 3) Then
    Debug.Print "Unexpected AuthFlowState:" & oauth2.AuthFlowState
    Exit Sub
End If

Debug.Print "OAuth2 authorization granted!"

Dim json As New ChilkatJsonObject
success = json.Load(oauth2.AccessTokenResponse)
json.EmitCompact = 0

Debug.Print "Access Token Response = " & json.Emit()

' A sample access token response:

' {
'   "access_token": "...",
'   "token_type": "bearer",
'   "expires_in": 14399,
'   "refresh_token": "...",
'   "scope": "account_info.read",
'   "uid": "562542581",
'   "account_id": "dbid:AACQhDS0E3_Vb72Ynd0F-GxGWdTI2qcTHzA"
' }

Debug.Print "Access Token = " & oauth2.AccessToken

' Save the JSON access token response to a file for subsequent use..
success = json.WriteFile("qa_data/tokens/dropbox.json")