(Xojo Plugin) Dropbox: OAuth2 Authorization to Obtain an Access Token

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

Note: This example requires Chilkat v10.1.2 or greater.

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// For more information about the OAuth2, see OAuth 2.0 Authorization Flow

Dim oauth2 As New Chilkat.OAuth2

// 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 this with your actual Dropbox App Key
oauth2.ClientId = "DROPBOX_APP_KEY"

// This is for Require Proof Key for Code Exchange (PKCE)
// See OAuth2 PKCE Explained
oauth2.CodeChallenge = True
oauth2.CodeChallengeMethod = "S256"

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

// Begin the OAuth2 Authorization code 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

System.DebugLog("url = " + url)

// Launch the default browser on the system and navigate to the url.
// The LaunchBrowser method was added in Chilkat v10.1.2.
Dim success As Boolean
success = oauth2.LaunchBrowser(url)
If (success = False) Then
    System.DebugLog(oauth2.LastErrorText)
    Return
End If

// Wait for the user to approve or deny authorization in the browser.
Dim numMsWaited As Int32
numMsWaited = 0
While (numMsWaited < 90000) And (oauth2.AuthFlowState < 3)
    oauth2.SleepMs 100
    numMsWaited = numMsWaited + 100
Wend

// 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
    success = oauth2.Cancel()
    System.DebugLog("No response from the browser!")
    Return
End If

// 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
    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!")

Dim json As New Chilkat.JsonObject
success = json.Load(oauth2.AccessTokenResponse)
json.EmitCompact = False

System.DebugLog("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"
// }

System.DebugLog("Access Token = " + oauth2.AccessToken)

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