Consume ABP API from Flutter App

If you are using the ABP Framework and want to authenticate and consume it in your Flutter application, please read further where I will give a short guide on how to implement the changes needed in your application.

I will not go in much detail about the actual Flutter code implementation neither the ABP implemnentation, as this is a simple example of how it can be done.

Nor can I be held responsible for any bugs, breaches or unaware use of packages.

Requirements

  • Existing ABP API project with IdentityServer
  • Existing Flutter application

Setup API

First we need to setup our backend project, to enable another client, that is allowed to consume the API endpoints and thus make requests. Since we are using our YourProject.DbMigrator project to setup clients initially, we also need to add the new client from it's appsettings.

Remember to change "YourProject" with the right name of your project 😉

YourProject.DbMigrator/appsettings.json

Add the below code to the "IdentityServer" "Clients" section:

"YourProjectApi_App": {
  "ClientId": "YourProjectApi_App",
  "ClientSecret": "SomeSecretValue",
  "RootUrl": "https://localhost:44349"
  // RootUrl = "AuthServer:Authority": "https://localhost:44349" in appsettings.json HttpApi.Host project
}

YourProject.Domain/IdentityServer/IdentityServerDataSeedContributor.cs

Add the below code after the last "Swagger Client", as shown below:

// Flutter App Client
var appClientId = configurationSection["YourProjectApi_App:ClientId"];
if (!appClientId.IsNullOrWhiteSpace())
{
  var appRootUrl = configurationSection["YourProjectApi_App:RootUrl"].TrimEnd('/');

  await CreateClientAsync(
    name: appClientId,
    scopes: commonScopes,
    grantTypes: new[] { "authorization_code", "client_credentials" },
    secret: configurationSection["YourProjectApi_App:ClientSecret"]?.Sha256(),
    requireClientSecret: false,
    redirectUri: "com.example.app://callback",
    corsOrigins: new[] { appRootUrl.RemovePostFix("/") }
  );
}

Be sure to run your DbMigrator project to update your database with the new client defined above. Else our Flutter app will not be able to authenticate and use the API endpoints.

Setup Flutter App

Remember to change "YourProject" with the right name of your project 😉

We need to add the "flutter_appauth" package from this repository https://github.com/MaikuB/flutter_appauth in the dependencies section in the pubspec file, as shown below:

YourApp/pubspec.yaml

dependencies:
  flutter:
    sdk: flutter
  flutter_appauth: ^0.9.1

Next up we will create a simple widget with a button, that can handle the upcoming login action:

YourApp/lib/ui/view/auth/widgets/login.dart

  
import 'package:flutter/material.dart';

class Login extends StatelessWidget {
  final loginAction;
  final String loginError;

  const Login(this.loginAction, this.loginError);

  @override
  Widget build(BuildContext context) {
    return Column(
      mainAxisAlignment: MainAxisAlignment.center,
      children: <Widget>[
        RaisedButton(
          onPressed: () {
            loginAction();
          },
          child: Text('Login'),
        ),
        Text(loginError ?? ''),
      ],
    );
  }
}

Next we will create a model for use in our auth. The model will hold the accessToken, which can be used in subsequent requests to the API. The model also holds some simple methods to retrieve users, and user details for the the user requesting.

YourApp/lib/core/models/yourapi_api.dart

import 'dart:convert';
import 'dart:io';
import 'package:http/http.dart';
import 'package:http/http.dart' as http;


class YourProjectAPI {
  static String accessToken;
  static const String _baseUrl =
      "https://your-api/api";
  static Map<String, String> headers = {
    'Content-type': 'application/json',
    'Accept': 'application/json',
    HttpHeaders.authorizationHeader: "Bearer $accessToken",
  };

  static Future<Response> getUserDetails() async {
    final url = '$_baseUrl/identity/my-profile';
    final response = await http.get(
      url,
      headers: {HttpHeaders.authorizationHeader: "Bearer $accessToken"},
    );

    return response;
  }

  // Example API method call
  static Future<List<User>> getUsers() async {
    final response = await http.get("$_baseUrl/identity/users", headers: headers);

    
    if (response.statusCode == 200) {
      // Logic here       
    }
    return response;
  }
}

Next we will create a view with our auth functionality. The main things to be aware of here is the constants: "DOMAIN", "CLIENT_ID", "CLIENT_SECRET" and "REDIRECT_URI". "CLIENT_ID", "CLIENT_SECRET" and "REDIRECT_URI" of course needs to be the same, defined previously in the API.

The views sole purpose is to handle the "Login" button clicked, fire a request towards the API's authentication endpoint and retrieve token, which needs to be parsed, saved in securestorage and used in subsequent requests.

YourApp/lib/ui/view/auth/auth.dart

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:flutter_appauth/flutter_appauth.dart';
import 'package:flutter_secure_storage/flutter_secure_storage.dart';
import 'package:yourapp/ui/view/auth/widgets/login.dart';
import 'package:yourapp/core/models/yourprojectapi_api.dart';

final FlutterAppAuth appAuth = FlutterAppAuth();
final FlutterSecureStorage secureStorage = const FlutterSecureStorage();

// YourProject Api details
const DOMAIN = '10.0.2.2:44349'; // 10.0.2.2 used here due to localhost cannot be resolved.
const CLIENT_ID = 'YourProjectApi_App';
const CLIENT_SECRET = "SomeSecretValue";

const REDIRECT_URI = 'com.example.app://callback';
const ISSUER = 'https://$DOMAIN';

class Auth extends StatefulWidget {
  static const route = "/newauth";

  @override
  _AuthState createState() => _AuthState();
}

class _AuthState extends State<Auth> {
  bool isBusy = false;
  bool isLoggedIn = false;
  String errorMessage;
  String name;
  String picture;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: isBusy
            ? CircularProgressIndicator()
            : Login(loginAction, errorMessage),
      ),
    );
  }

  Map<String, dynamic> parseIdToken(String idToken) {
    final parts = idToken.split(r'.');
    assert(parts.length == 3);

    return jsonDecode(
        utf8.decode(base64Url.decode(base64Url.normalize(parts[1]))));
  }

  getUserDetails() async {
    var profileDetails = {};
    YourProjectAPI.getUserDetails().then(
      (response) {
        if (response.statusCode == 200) {
          profileDetails = jsonDecode(response.body);
        } else {
          throw Exception('Failed to get user details');
        }
      },
    );
    return profileDetails;
  }

  Future<void> loginAction() async {
    setState(() {
      isBusy = true;
      errorMessage = '';
    });

    try {
      final AuthorizationTokenResponse result =
          await appAuth.authorizeAndExchangeCode(
        AuthorizationTokenRequest(CLIENT_ID, REDIRECT_URI,
            clientSecret: CLIENT_SECRET,
            issuer: 'https://$DOMAIN',
            scopes: ["email", "openid", "profile", "role", "phone", "address"],
            promptValues: ['login']),
      );

      // Set access token for application
      YourProjectAPI.accessToken = result.accessToken;

      final idToken = parseIdToken(result.idToken);
      final profile = await getUserDetails();
      await secureStorage.write(
          key: 'refresh_token', value: result.refreshToken);

      // This setstate is most likely not needed
      setState(() {
        isBusy = false;
        isLoggedIn = true;
        name = idToken['name'];
        picture = profile['picture'];
      });
    } catch (e, s) {
      print('login error: $e - stack: $s');
      setState(() {
        isBusy = false;
        isLoggedIn = false;
        errorMessage = e.toString();
      });
    }
  }

  @override
  void initState() {
    initAction();
    super.initState();
  }

  void initAction() async {
    final storedRefreshToken = await secureStorage.read(key: 'refresh_token');
    if (storedRefreshToken == null) return;

    setState(() {
      isBusy = true;
    });

    try {
      final response = await appAuth.token(TokenRequest(
        CLIENT_ID,
        REDIRECT_URI,
        issuer: ISSUER,
        refreshToken: storedRefreshToken,
      ));

      final idToken = parseIdToken(response.idToken);
      final profile = await getUserDetails();

      secureStorage.write(key: 'refresh_token', value: response.refreshToken);

      setState(() {
        isBusy = false;
        isLoggedIn = true;
        name = idToken['name'];
        picture = profile['picture'];
      });
    } catch (e, s) {
      print('error on refresh token: $e - stack: $s');
      setState(() {
        isBusy = false;
        isLoggedIn = false;
      });
    }
  }
}

YourApp/android/app/build.gradle

We also need the below line for Android configuration to let the app to be redirected back to

android {
    defaultConfig {
        ...
        manifestPlaceholders = [
                'appAuthRedirectScheme': 'com.example.app'
        ]
    }
}

And for IOS:

<key>CFBundleURLTypes</key>
	<array>
		<dict>
			<key>CFBundleTypeRole</key>
			<string>Editor</string>
			<key>CFBundleURLSchemes</key>
			<array>
				<string>com.example.app</string>
			</array>
		</dict>
	</array>

Test

With the above code implementation, we can now run our app in an Android emulator, and we should be able to have a login screen shown.

When clicking on the "Login" button, a browser should open with a our well known login screen from the API project - and then let us login and be sent back to the app!

login 

Notes

Example repository: https://github.com/Znow/ConsumeAbpFromFlutterApp

  • Getting connection issues? Be sure that your SSL certificate is trusted if using https.
  • If any questions/thoughts/ideas/changes - Please send me a message, and I will get back to you.
Registration Date
4/23/2021