FlutterでAndroidでのAuth0のログイン・ログアウトを実装してみた

# (一部抜粋)
dependencies:
  flutter:
    sdk: flutter
  flutter_appauth:
  http:
  flutter_riverpod:
  url_launcher:
  cupertino_icons: ^1.0.8

dev_dependencies:
  flutter_test:
    sdk: flutter
  flutter_lints: ^5.0.0

import 'package:flutter/material.dart';
import 'package:flutter_riverpod/flutter_riverpod.dart';
import 'package:flutter_appauth/flutter_appauth.dart';
import 'package:url_launcher/url_launcher.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';

final authProvider = Provider<AuthService>((ref) => AuthService());

void main() {
  runApp(
    ProviderScope(
      child: MyApp(),
    ),
  );
}

class AuthService {
  final FlutterAppAuth _appAuth = FlutterAppAuth();

  // Auth0の設定
  final String _clientId = '{clientId}';
  final String _domain = '{domain}';
  // schemeはbuild.gradleのnamespaceにある"com.example.test"のような形式
  final String _redirectUri = 'com.example.appauth2://callback';
  final String _issuer = 'https://{$_domain}';

  Future<void> login() async {
    try {
      final AuthorizationTokenResponse? result =
        await _appAuth.authorizeAndExchangeCode(
          AuthorizationTokenRequest(
            _clientId,
            _redirectUri,
            issuer: _issuer,
            scopes: ['openid', 'profile', 'email'],
          ),
        );
      if (result != null) {
        final userInfoResponse = await http.get(
          Uri.https('$_domain', '/userinfo'),
          headers: {'Authorization': 'Bearer ${result.accessToken}'},
        );
        final userInfo = jsonDecode(userInfoResponse.body);
        String? email = userInfo['email'];
        print('ログイン成功: $email');
      } else {
        print('結果がnull');
      }
    } catch (e) {
      print('ログインエラー: $e');
    }
  }

  Future<void> logout() async {
    try {
      final url = Uri.https(
        '$_domain',
        '/v2/logout',
        {
          'returnTo': _redirectUri,
          'client_id': _clientId,
        },
      );
      if (await canLaunchUrl(url)) {
        await launchUrl(url, mode: LaunchMode.externalApplication);
        print('ログアウト成功');
      } else {
          throw 'ログアウトURLを開けませんでした';
      }
    } catch (e) {
      print('ログアウトエラー: $e');
    }
  }
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Auth0 test',
      home: HomePage(),
    );
  }
}

class HomePage extends ConsumerWidget {
  @override
  Widget build(BuildContext context, WidgetRef ref) {
    final auth = ref.read(authProvider);

    return Scaffold(
      appBar: AppBar(
        title: Text('Auth0 test'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            ElevatedButton(
              onPressed: () async {
                await auth.login();
              },
              child: Text('ログイン'),
            ),
            ElevatedButton(
              onPressed: () async {
                await auth.logout();
              },
              child: Text('ログアウト'),
            ),
          ],
        ),
      ),
    );
  }
}

defaultConfig {
  applicationId = "com.example.appauth2"
  minSdk = flutter.minSdkVersion
  targetSdk = flutter.targetSdkVersion
  versionCode = flutter.versionCode
  versionName = flutter.versionName
  // この部分を追加
  manifestPlaceholders += [
      'appAuthRedirectScheme': 'com.example.appauth2'
  ]
}

  <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="com.example.appauth2"
      android:host="callback"
      android:path="/" />
  </intent-filter>

I/flutter (10046): ログイン成功: {emailアドレス}
I/UrlLauncher(10046): component name for https://{domain}/v2/logout?returnTo=com.example.appauth2...
I/flutter (10046): ログアウト成功
W/AppAuth (10046): No stored state - unable to handle response