Flutter Firebase Authentication: Apple Sign In

flutter create flutter_apple_signin

dependencies:
  flutter:
    sdk: flutter
  firebase_core: "^0.7.0"
  firebase_auth: "^0.20.0+1"
  sign_in_with_apple: ^2.5.2
  crypto: ^2.1.5
  provider: ^4.3.3

import 'dart:convert';
import 'dart:math';

import 'package:crypto/crypto.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:sign_in_with_apple/sign_in_with_apple.dart';

class AuthenticationProvider with ChangeNotifier {
  final FirebaseAuth _firebaseAuth;

  AuthenticationProvider(this._firebaseAuth);

  Stream<User> get authStateChanges => _firebaseAuth.authStateChanges();

  Future<void> signOut() async {
    await _firebaseAuth.signOut();
  }

  /// Generates a cryptographically secure random nonce, to be included in a
  /// credential request.
  String generateNonce([int length = 32]) {
    final charset =
        '0123456789ABCDEFGHIJKLMNOPQRSTUVXYZabcdefghijklmnopqrstuvwxyz-._';
    final random = Random.secure();
    return List.generate(length, (_) => charset[random.nextInt(charset.length)])
        .join();
  }

  /// Returns the sha256 hash of [input] in hex notation.
  String sha256ofString(String input) {
    final bytes = utf8.encode(input);
    final digest = sha256.convert(bytes);
    return digest.toString();
  }

  Future<User> signInWithApple() async {
    // To prevent replay attacks with the credential returned from Apple, we
    // include a nonce in the credential request. When signing in in with
    // Firebase, the nonce in the id token returned by Apple, is expected to
    // match the sha256 hash of `rawNonce`.
    final rawNonce = generateNonce();
    final nonce = sha256ofString(rawNonce);

    try {
      // Request credential for the currently signed in Apple account.
      final appleCredential = await SignInWithApple.getAppleIDCredential(
        scopes: [
          AppleIDAuthorizationScopes.email,
          AppleIDAuthorizationScopes.fullName,
        ],
        nonce: nonce,
      );

      print(appleCredential.authorizationCode);

      // Create an `OAuthCredential` from the credential returned by Apple.
      final oauthCredential = OAuthProvider("apple.com").credential(
        idToken: appleCredential.identityToken,
        rawNonce: rawNonce,
      );

      // Sign in the user with Firebase. If the nonce we generated earlier does
      // not match the nonce in `appleCredential.identityToken`, sign in will fail.
      final authResult =
          await _firebaseAuth.signInWithCredential(oauthCredential);

      final displayName =
          '${appleCredential.givenName} ${appleCredential.familyName}';
      final userEmail = '${appleCredential.email}';

      final firebaseUser = authResult.user;
      print(displayName);
      await firebaseUser.updateProfile(displayName: displayName);
      await firebaseUser.updateEmail(userEmail);

      return firebaseUser;
    } catch (exception) {
      print(exception);
    }
  }
}

import 'package:flutter/material.dart';
import 'package:flutter_apple_signin/providers/authentication_provider.dart';
import 'package:provider/provider.dart';

import 'package:sign_in_with_apple/sign_in_with_apple.dart';

class LoginPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Padding(
        padding: const EdgeInsets.all(8.0),
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            SignInWithAppleButton(
              style: SignInWithAppleButtonStyle.black,
              iconAlignment: IconAlignment.center,
              onPressed: () {
                context.read<AuthenticationProvider>().signInWithApple();
              },
            )
          ],
        ),
      ),
    );
  }
}

import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:firebase_core/firebase_core.dart';
import 'package:flutter_apple_signin/providers/authentication_provider.dart';
import 'package:flutter_apple_signin/screens/login_screen.dart';
import 'package:flutter_apple_signin/screens/logout_screen.dart';
import 'package:provider/provider.dart';

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MultiProvider(
      providers: [
        ChangeNotifierProvider(
          create: (ctx) => AuthenticationProvider(FirebaseAuth.instance),
        ),
        StreamProvider(
          create: (BuildContext context) {
            return context.read<AuthenticationProvider>().authStateChanges;
          },
        )
      ],
      child: MaterialApp(
        title: 'Flutter Demo',
        theme: ThemeData(
          primarySwatch: Colors.purple,
          accentColor: Colors.deepOrange,
          visualDensity: VisualDensity.adaptivePlatformDensity,
        ),
        home: MyHomePage(),
        routes: {},
      ),
    );
  }
}

class MyHomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final firebaseUser = context.watch<User>();
    return Scaffold(
        appBar: AppBar(
          title: Text('Apple Sign In'),
        ),
        body: firebaseUser != null ? LogoutPage() : LoginPage());
  }
}