Create an app in Autodesk

• First, create an account on Autodesk if you don’t have one already
• Go to https://aps.autodesk.com/myapps/ and create an app

• Give a meaningful name to the app, and make sure you choose “Desktop, Mobile, Single-Page App” from the options.

• Copy the client id and store it in the environment variable (check this story to know how to create and use environment variables in Flutter)

Setup callback URL

• Install the flutter package flutter_web_auth_2
• Form your callback URL in the pattern <some-schema>://<app-package-name>, e.g., sample_schema://com.your_company.app_name. Note this URL
• In the Autodesk app, that you just created, in addition to http://localhost:8080/ add the callback URL you just formed
• For Android, update the AndroidManifest.xml as below, and add activity as below

<activity android:name=“com.linusu.flutter_web_auth_2.CallbackActivity” android:exported=“true”>
<intent-filter android:label=“flutter_web_auth_2”>
<action android:name=“android.intent.action.VIEW” />
<category android:name=“android.intent.category.DEFAULT” />
<category android:name=“android.intent.category.BROWSABLE” />
<data android:scheme=“sample_schema” android:host = “com.your_company.app_name” />
</intent-filter>
</activity>

• In iOS, for “normal” authentication, just use this library as usual; there is nothing special to do. To authenticate using Universal Links on iOS, use https as the provided callbackUrlScheme

final result = await FlutterWebAuth2.authenticate(url: "https://my-custom-app.com/connect", callbackUrlScheme: "https");

Login user

• We need to log in the user in 2 steps, get the authorization code and then use it to get the auth token of the user
• To get the authorization code, you can call the API https://developer.api.autodesk.com/authentication/v2/authorize as below

  @override
  Future<bool> login() async {
    final authorizationUrl = Uri.parse(
      'https://developer.api.autodesk.com/authentication/v2/authorize',
    ).replace(
      queryParameters: {
        'client_id': Environment.clientId,
        'response_type': 'code',
        'redirect_uri': Environment.callbackUrl, // The callback URL you formed
        'scope': 'data:read',
        'code_challenge': Environment.codeChallenge,
      },
    ).toString();

    try {
      final result = await FlutterWebAuth2.authenticate(
        url: authorizationUrl,
        callbackUrlScheme: Environment.customUriScheme, // Part of the callback URL you formed
      );

      final uri = Uri.parse(result);
      authorizationCode = uri.queryParameters['code'] ?? '';

      return _getAccessToken();
    } catch (e) {
      Dependency.logging.error('Error during authentication: $e');
      return false;
    }
  }

• Now use the authorization code to get the access token using the API https://developer.api.autodesk.com/authentication/v2/token as

 Future<bool> _getAccessToken() async {
    final tokenUrl = Uri.parse(
      'https://developer.api.autodesk.com/authentication/v2/token',
    ).toString();
    final response = await Dependency.network.post(
      Uri.parse(tokenUrl),
      body: {
        'clientId': Environment.clientId,
        'grantType': 'authorization_code',
        'code': authorizationCode,
        'redirectUri': Environment.callbackUrl,
        'codeVerifier': Environment.codeChallenge,
      },
      authenticateRequest: false,
    );

    Map<String, dynamic>? responseJson;

    try {
      responseJson = jsonDecode(response.body);
    } catch (e) {
      Dependency.logging.error('Unable to parse the response: $e');
      return false;
    }

    final accessTokenData = AccTokenResponse.fromJson(responseJson!);

    // accessTokenData.accessToken -> Your access token

    return true;
  }

That’s it! Now you can use this access token to call the other APIs of Autodesk.

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