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Using Web3Auth Flutter SDK

mobileflutterwhitelabelcustom authenticationdapp shareblockchainWeb3Auth Team | September 13, 2022

This guide will cover the basics of how to use the Web3Auth Flutter SDK in your Flutter application and make blockchain calls to get access to user's account, fetch balance, sign transaction, and send transaction.

Repository: https://github.com/Web3Auth/web3auth-pnp-examples//raw/main/flutter/flutter-example

Quick Start​

npx degit Web3Auth/web3auth-pnp-examples/flutter/flutter-example w3a-flutter-demo
cd w3a-flutter-demo
# Open in Android Studio or VS Code
flutter run

How it works?​

When integrating Web3Auth Flutter SDK with Social Login the flow looks something like this:

Web3Auth Core - Social Login Flow

  • When a user logs in with Google, Google sends a JWT id_token to the app. This JWT token is sent to the Web3Auth SDK's login function.

  • Finally, on successful validation of the JWT token, Web3Auth SDK will generate a private key for the user, in a self custodial way, resulting in easy onboarding for your user to the application.

Prerequisites​

  • For Web Apps: A basic knowledge of JavaScript is required to use Web3Auth SDK.

  • For Mobile Apps: For the Web3Auth Mobile SDKs, you have a choice between iOS, Android, React Native & Flutter. Please refer to the Web3Auth SDK Reference for more information.

  • Create a Web3Auth account on the Web3Auth Dashboard

  • Android API version 24 or newer.
  • For Android build: compileSdkVersion needs to be 32. Check android/app/build.gradle in your Flutter project to change it.
  • iOS 12+
  • Xcode 11.4+ / 12.x
  • Swift 4.x / 5.x
  • For iOS build: platform :ios needs to be 13.0. Check ios/Podfile in your Flutter project to change it.

Setup​

Setup your Web3Auth Dashboard​

  • Create a Project from the Project Section of the Web3Auth Developer Dashboard.

    Plug n Play Project Creation on Web3Auth Dashboard

    • Enter your desired Project name.

    • Select the Product you want to use. For this guide, we'll be using the Plug n Play product.

    • Select the Platform type you want to use. For this guide, we'll be using the Web Application as the platform.

    • Select the Web3Auth Network as Sapphire Devnet. We recommend creating a project in the sapphire_devnet or tesnet network during development. While moving to a production environment, make sure to convert your project to sapphire_mainnet or any of the legacy mainnet network mainnet, aqua, or cyan network. Otherwise, you'll end up losing users and keys.

    • Select the blockchain(s) you'll be building this project on. For interoperability with Torus Wallets, you have the option of allowing the user's private key to be used in other applications using Torus Wallets (EVM, Solana, XRPL & Casper).

    • Finally, once you create the project, you have the option to whitelist your URLs for the project. Please whitelist the domains where your project will be hosted.

      Plug n Play Project - Whitelist

  • Add {SCHEME}://{YOUR_APP_PACKAGE_NAME} (e.g, w3a://com.example.w3aflutter) for Android and {bundleId}://openlogin (e.g, com.example.w3aflutter://openlogin) for iOS in the Whitelist URL field of the Web3Auth Dashboard.

Using the Web3Auth SDK​

To use the Web3Auth SDK, you need to add the dependency of the respective platform SDK of Web3Auth to your project. To know more about the available SDKs, please have a look at this documentation page.

For this guide, we will be using the Web3Auth Flutter SDK.

Installation​

Add web3auth_flutter as a dependency to your pubspec.yaml

dependencies:
  web3auth_flutter: ^2.0.3

or

flutter pub add web3auth_flutter

Add Web3Auth to Gradle​

In your project-level's build.gradle file, add JitPack repository:

dependencyResolutionManagement {
    repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
    repositories {
        google()
        mavenCentral()
        maven { url "https://jitpack.io" } // <-- Add this line
    }
}

Then, in your app-level build.gradle dependencies section, add the following:

dependencies {
    implementation 'com.github.Web3Auth:web3auth-android-sdk:4.0.8'
}

Permissions​

Open your app's AndroidManifest.xml file and add the following permission:

<uses-permission android:name="android.permission.INTERNET" />

Note: The <uses-permission> element must be a direct child of the <manifest> root element.

Configuration​

Configure a Plug n Play project​

  • Go to Developer Dashboard, create or select a Web3Auth project:

  • Add {SCHEME}://{YOUR_APP_PACKAGE_NAME} to Whitelist URLs. eg. w3a://com.example.w3aflutter

  • Copy the Client ID for usage later.

Open your app's AndroidManifest.xml file and add the following deep link intent filter to your sign-in activity:

<intent-filter>
  <action android:name="android.intent.action.VIEW" />

  <category android:name="android.intent.category.DEFAULT" />
  <category android:name="android.intent.category.BROWSABLE" />

  <data android:scheme="{scheme}" android:host="{YOUR_APP_PACKAGE_NAME}" android:path="/auth" />
  <!-- Accept URIs: w3a://com.example.w3aflutter -->
</intent-filter>

Make sure your sign-in activity launchMode is set to singleTop in your AndroidManifest.xml

<activity
  android:launchMode="singleTop"
  android:name=".YourActivity">
  // ...
</activity>

Initialization​

After Installation, the next step to use Web3Auth is to Initialize the SDK. This can be achieved by using the init() function.

Please note that these are the most critical steps where you need to pass on different parameters according to the preference of your project. Additionally, Whitelabeling and Custom Authentication have to be configured within this step, if you wish to customise your Web3Auth Instance.

Create Web3Auth Instance​

In your main.dart file, initialise the Web3AuthFlutter plugin at the very beginning such as in the overriden initState function

import 'dart:collection';
import 'dart:io';
import 'dart:async';

import 'package:web3auth_flutter/web3auth_flutter.dart';
import 'package:web3auth_flutter/enums.dart';
import 'package:web3auth_flutter/input.dart';
import 'package:web3auth_flutter/output.dart';

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

// Initialization
Future<void> initPlatformState() async {
  HashMap themeMap = new HashMap<String, String>();
  themeMap['primary'] = "#fff000";

  Uri redirectUrl;
  if (Platform.isAndroid) {
    redirectUrl = Uri.parse('{SCHEME}://{HOST}/auth');
    // w3a://com.example.w3aflutter/auth
  } else if (Platform.isIOS) {
    redirectUrl = Uri.parse('{bundleId}://openlogin');
    // com.example.w3aflutter://openlogin
  } else {
    throw UnKnownException('Unknown platform');
  }
  await Web3AuthFlutter.init(Web3AuthOptions(
    clientId:'YOUR WEB3AUTH CLIENT ID FROM DASHBOARD',
    network: Network.cyan,
    redirectUri: redirectUrl,
  ));
}

Read more about initialising the Flutter SDK here.

Authentication​

Logging in​

Once initialized, you can use the Web3AuthFlutter.login(LoginParams( loginProvider: Provider.google )) function to authenticate the user when they click the login button.

VoidCallback _login(Future<Web3AuthResponse> Function() method) {
  return () async {
    try {
      final Web3AuthResponse response = await method();
      setState(() {
        _result = response.toString();
        logoutVisible = true;
      });
    } on UserCancelledException {
      print("User cancelled.");
    } on UnKnownException {
      print("Unknown exception occurred");
    }
  };
}

Future<Web3AuthResponse> _withGoogle() {
  return Web3AuthFlutter.login(LoginParams(
    loginProvider: Provider.google,
    mfaLevel: MFALevel.OPTIONAL,
  ));
}

When connecting, the login function takes the LoginParams arguments for the login. See the LoginParams for more details.

Sample loginResponse​

{
  "privKey": "0ajjsdsd....",
  "userInfo": {
    "name": "John Dash",
    "profileImage": "https://lh3.googleusercontent.com/a/Ajjjsdsmdjmnm...",
    "typeOfLogin": "google",
    "aggregateVerifier": "tkey-google",
    "verifier": "torus",
    "verifierId": "john@gmail.com",
    "email": "john@gmail.com",
    "dappShare": "<24 words seed phrase>", // will be sent only incase of custom verifiers
    "idToken": "<jwtToken issued by Web3Auth>",
    "oAuthIdToken": "<jwtToken issued by OAuth Provider>", // will be sent only incase of custom verifiers
    "oAuthAccessToken": "<accessToken issued by OAuth Provider>" // will be sent only incase of custom verifiers
  },
  "ed25519PrivKey": "666523652352635....",
  "coreKitKey": "0xajjsdsd....",
  "coreKitEd25519PrivKey": "666523652352635....",
  "sessionId": "0xajjsdsd...."
}

Get the User Profile​

// Assuming the user is logged in, get the user profile from the web3AuthResponse
userInfo = web3AuthResponse.userInfo

Using the web3AuthFlutter.login function, you can get the details of the logged in user. Please note that these details are not stored anywhere in Web3Auth network.

If you wish you add Multi Factor Authentication, use dApp Share or select Curve for your Android application, read the linked documentation.

Logout​

VoidCallback _logout() {
  return () async {
    try {
      await Web3AuthFlutter.logout();
      setState(() {
        _result = '<empty>';
        logoutVisible = false;
      });
    } on UserCancelledException {
      print("User cancelled.");
    } on UnKnownException {
      print("Unknown exception occurred");
    }
  };
}

Logging out your user is as simple as calling the web3AuthFlutter.logout() function.

UI in this guide​

@override
  Widget build(BuildContext context) {
    // Map<String, dynamic> user = jsonDecode(_result);

    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Web3Auth x Flutter Example'),
        ),
        body: SingleChildScrollView(
          child: Center(
              child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              const Padding(
                padding: EdgeInsets.all(8.0),
              ),
              Visibility(
                visible: !logoutVisible,
                child: Column(
                  children: [
                    const Icon(
                      Icons.flutter_dash,
                      size: 80,
                      color: Color(0xFF1389fd),
                    ),
                    const SizedBox(
                      height: 40,
                    ),
                    const Text(
                      'Web3Auth',
                      style: TextStyle(
                          fontWeight: FontWeight.bold,
                          fontSize: 36,
                          color: Color(0xFF0364ff)),
                    ),
                    const SizedBox(
                      height: 10,
                    ),
                    const Text(
                      'Welcome to Web3Auth x Flutter Demo',
                      style: TextStyle(fontSize: 14),
                    ),
                    const SizedBox(
                      height: 20,
                    ),
                    const Text(
                      'Login with',
                      style: TextStyle(fontSize: 12),
                    ),
                    const SizedBox(
                      height: 20,
                    ),
                    ElevatedButton(
                        onPressed: _login(_withGoogle),
                        child: const Text('Google')),
                    ElevatedButton(
                        onPressed: _login(_withFacebook),
                        child: const Text('Facebook')),
                    ElevatedButton(
                        onPressed: _login(_withEmailPasswordless),
                        child: const Text('Email Passwordless')),
                    ElevatedButton(
                        onPressed: _login(_withDiscord),
                        child: const Text('Discord')),
                  ],
                ),
              ),
              Visibility(
                // ignore: sort_child_properties_last
                child: Column(
                  children: [
                    Center(
                      child: ElevatedButton(
                          style: ElevatedButton.styleFrom(
                              backgroundColor:
                                  Colors.red[600] // This is what you need!
                              ),
                          onPressed: _logout(),
                          child: Column(
                            children: const [
                              Text('Logout'),
                            ],
                          )),
                    ),
                  ],
                ),
                visible: logoutVisible,
              ),
              Padding(
                padding: const EdgeInsets.all(8.0),
                child: Text(_result),
              )
            ],
          )),
        ),
      ),
    );
  }

Interacting with the Blockchain​

Blockchain calls

Checkout the full codes to interact with ETH Blockchain.

Get Account​

import 'package:web3dart/web3dart.dart';
import 'package:shared_preferences/shared_preferences.dart';

// checkout the Connect Blockchain > Ethereum > Flutter to get full code.

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: Center(
            child:
            Column(mainAxisAlignment: MainAxisAlignment.center, children: [
              // Get Account
              ElevatedButton(
                onPressed: () async {
                  final credentials = EthPrivateKey.fromHex(privateKey);
                  final address = credentials.address;
                  debugPrint("Account, ${address.hexEip55}");
                },
                child: const Text('Get Address'),
              ),
            ])));
  }

Get Balance​

import 'package:web3dart/web3dart.dart';
import 'package:shared_preferences/shared_preferences.dart';

// checkout the Connect Blockchain > Ethereum > Flutter to get full code.

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: Center(
            child:
            Column(mainAxisAlignment: MainAxisAlignment.center, children: [
              // Get Balance
              ElevatedButton(
                onPressed: () async {
                  final prefs = await SharedPreferences.getInstance();
                  final privateKey = prefs.getString('privateKey') ?? '0';
                  final credentials = EthPrivateKey.fromHex(privateKey);
                  final client = Web3Client(rpcUrl, Client());
                  final credentials = EthPrivateKey.fromHex(privateKey);
                  final address = credentials.address;
                  final balance = await client.getBalance(address);
                  debugPrint("Balance, ${balance}");
                },
                child: const Text('Get Balance'),
              ),
            ])));
  }

Send Transaction​

import 'package:web3dart/web3dart.dart';
import 'package:shared_preferences/shared_preferences.dart';

// checkout the Connect Blockchain > Ethereum > Flutter to get full code.

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: Center(
            child:
            Column(mainAxisAlignment: MainAxisAlignment.center, children: [
              // Send Transaction
              ElevatedButton(
                onPressed: () async {
                  final prefs = await SharedPreferences.getInstance();
                  final privateKey = prefs.getString('privateKey') ?? '0';
                  final client = Web3Client(rpcUrl, Client());
                  final credentials = EthPrivateKey.fromHex(privateKey);
                  final address = credentials.address;
                  final receipt = await client.sendTransaction(
                      credentials,
                      Transaction(
                        from: address,
                        to: EthereumAddress.fromHex(
                            '0x809D4310d578649D8539e718030EE11e603Ee8f3'),
                        value: EtherAmount.fromUnitAndValue(
                            EtherUnit.gwei, 5000000), // 0.005 ETH
                      ),
                      chainId: 5); // change chainId as per your chain.
                  debugPrint("Receipt, ${receipt}");
                },
                child: const Text('Send Transaction'),
              ),
            ])));
  }

Example code​

The code for the application we developed in this guide can be found in the Web3Auth Flutter Example. Check it out and try running it locally yourself!

flutter run

Also, checkout other examples:

Questions?​

Ask us on Web3Auth's Community Portal