Flutter Navigation 2.0とGoRouter 2026年完全ガイド：ディープリンクから面接対策まで

// Raw Navigator 2.0 approach - verbose and rarely used directly
class AppRouterDelegate extends RouterDelegate<AppRoutePath>
    with ChangeNotifier, PopNavigatorRouterDelegateMixin<AppRoutePath> {
  @override
  final GlobalKey<NavigatorState> navigatorKey = GlobalKey<NavigatorState>();

  AppRoutePath? _currentPath;

  @override
  AppRoutePath? get currentConfiguration => _currentPath;

  @override
  Widget build(BuildContext context) {
    return Navigator(
      key: navigatorKey,
      pages: [
        const MaterialPage(child: HomeScreen()),
        if (_currentPath?.isProductPage == true)
          MaterialPage(child: ProductScreen(id: _currentPath!.productId!)),
      ],
      onDidRemovePage: (page) {
        // Handle page removal
      },
    );
  }

  @override
  Future<void> setNewRoutePath(AppRoutePath path) async {
    _currentPath = path;
    notifyListeners();
  }
}

import 'package:go_router/go_router.dart';

final goRouter = GoRouter(
  initialLocation: '/',
  debugLogDiagnostics: true, // Useful during development
  routes: [
    GoRoute(
      path: '/',
      name: 'home',
      builder: (context, state) => const HomeScreen(),
      routes: [
        GoRoute(
          path: 'products/:id', // Path parameter
          name: 'product',
          builder: (context, state) {
            final productId = state.pathParameters['id']!;
            return ProductScreen(productId: productId);
          },
        ),
        GoRoute(
          path: 'search',
          name: 'search',
          builder: (context, state) {
            // Query parameters: /search?q=flutter&category=books
            final query = state.uri.queryParameters['q'] ?? '';
            final category = state.uri.queryParameters['category'];
            return SearchScreen(query: query, category: category);
          },
        ),
      ],
    ),
  ],
);

import 'package:flutter/material.dart';
import 'router_config.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp.router(
      routerConfig: goRouter,
      title: 'GoRouter Demo',
    );
  }
}

<!-- android/app/src/main/AndroidManifest.xml -->
<activity android:name=".MainActivity">
  <intent-filter android:autoVerify="true">
    <action android:name="android.intent.action.VIEW" />
    <category android:name="android.intent.category.DEFAULT" />
    <category android:name="android.intent.category.BROWSABLE" />
    <data
      android:scheme="https"
      android:host="example.com"
      android:pathPrefix="/products" />
  </intent-filter>
</activity>

{
  "applinks": {
    "apps": [],
    "details": [
      {
        "appID": "TEAMID.com.example.app",
        "paths": ["/products/*", "/search"]
      }
    ]
  }
}

final goRouter = GoRouter(
  initialLocation: '/home',
  routes: [
    ShellRoute(
      builder: (context, state, child) {
        return ScaffoldWithNavBar(child: child);
      },
      routes: [
        GoRoute(
          path: '/home',
          name: 'home',
          builder: (context, state) => const HomeTab(),
        ),
        GoRoute(
          path: '/explore',
          name: 'explore',
          builder: (context, state) => const ExploreTab(),
        ),
        GoRoute(
          path: '/profile',
          name: 'profile',
          builder: (context, state) => const ProfileTab(),
        ),
      ],
    ),
  ],
);

// scaffold_with_nav_bar.dart
class ScaffoldWithNavBar extends StatelessWidget {
  final Widget child;
  const ScaffoldWithNavBar({super.key, required this.child});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: child,
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: _calculateSelectedIndex(context),
        onTap: (index) => _onItemTapped(index, context),
        items: const [
          BottomNavigationBarItem(icon: Icon(Icons.home), label: 'Home'),
          BottomNavigationBarItem(icon: Icon(Icons.explore), label: 'Explore'),
          BottomNavigationBarItem(icon: Icon(Icons.person), label: 'Profile'),
        ],
      ),
    );
  }

  int _calculateSelectedIndex(BuildContext context) {
    final location = GoRouterState.of(context).uri.toString();
    if (location.startsWith('/explore')) return 1;
    if (location.startsWith('/profile')) return 2;
    return 0;
  }

  void _onItemTapped(int index, BuildContext context) {
    switch (index) {
      case 0: context.go('/home');
      case 1: context.go('/explore');
      case 2: context.go('/profile');
    }
  }
}

final goRouter = GoRouter(
  initialLocation: '/home',
  routes: [
    StatefulShellRoute.indexedStack(
      builder: (context, state, navigationShell) {
        return ScaffoldWithNavBar(navigationShell: navigationShell);
      },
      branches: [
        StatefulShellBranch(
          routes: [
            GoRoute(
              path: '/home',
              builder: (context, state) => const HomeTab(),
              routes: [
                GoRoute(
                  path: 'details/:id',
                  builder: (context, state) => DetailsScreen(
                    id: state.pathParameters['id']!,
                  ),
                ),
              ],
            ),
          ],
        ),
        StatefulShellBranch(
          routes: [
            GoRoute(
              path: '/explore',
              builder: (context, state) => const ExploreTab(),
            ),
          ],
        ),
        StatefulShellBranch(
          routes: [
            GoRoute(
              path: '/profile',
              builder: (context, state) => const ProfileTab(),
            ),
          ],
        ),
      ],
    ),
  ],
);

final goRouter = GoRouter(
  initialLocation: '/',
  redirect: (context, state) {
    final isLoggedIn = AuthService.instance.isLoggedIn;
    final isLoggingIn = state.matchedLocation == '/login';

    // Redirect to login if not authenticated
    if (!isLoggedIn && !isLoggingIn) {
      return '/login?redirect=${state.uri}';
    }

    // Redirect away from login if already authenticated
    if (isLoggedIn && isLoggingIn) {
      final redirect = state.uri.queryParameters['redirect'];
      return redirect ?? '/';
    }

    return null; // No redirect
  },
  routes: [
    GoRoute(
      path: '/',
      builder: (context, state) => const HomeScreen(),
    ),
    GoRoute(
      path: '/login',
      builder: (context, state) => const LoginScreen(),
    ),
    GoRoute(
      path: '/admin',
      redirect: (context, state) {
        // Route-level redirect for admin-only access
        if (!AuthService.instance.isAdmin) {
          return '/';
        }
        return null;
      },
      builder: (context, state) => const AdminScreen(),
    ),
  ],
);

// Passing via extra (not deep-linkable)
context.push('/product', extra: productObject);

// Receiving via extra
GoRoute(
  path: '/product',
  builder: (context, state) {
    final product = state.extra as Product?;
    return ProductScreen(product: product);
  },
),

import 'package:go_router/go_router.dart';

part 'routes.g.dart';

@TypedGoRoute<HomeRoute>(path: '/')
class HomeRoute extends GoRouteData {
  const HomeRoute();

  @override
  Widget build(BuildContext context, GoRouterState state) => const HomeScreen();
}

@TypedGoRoute<ProductRoute>(path: '/product/:id')
class ProductRoute extends GoRouteData {
  final String id;
  const ProductRoute({required this.id});

  @override
  Widget build(BuildContext context, GoRouterState state) =>
      ProductScreen(productId: id);
}

// Type-safe navigation
ProductRoute(id: '123').go(context);