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lib/13/go/exception_handling.dart

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+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+
+/// This sample app shows how to use `GoRouter.onException` to redirect on
+/// exception.
+///
+/// The first route '/' is mapped to [HomeScreen], and the second route
+/// '/404' is mapped to [NotFoundScreen].
+///
+/// Any other unknown route or exception is redirected to `/404`.
+void main() => runApp(const MyApp());
+
+/// The route configuration.
+final GoRouter _router = GoRouter(
+  onException: (_, GoRouterState state, GoRouter router) {
+    router.go('/404', extra: state.uri.toString());
+  },
+  routes: <RouteBase>[
+    GoRoute(
+      path: '/',
+      builder: (BuildContext context, GoRouterState state) {
+        return const HomeScreen();
+      },
+    ),
+    GoRoute(
+      path: '/404',
+      builder: (BuildContext context, GoRouterState state) {
+        return NotFoundScreen(uri: state.extra as String? ?? '');
+      },
+    ),
+  ],
+);
+
+/// The main app.
+class MyApp extends StatelessWidget {
+  /// Constructs a [MyApp]
+  const MyApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return MaterialApp.router(
+      routerConfig: _router,
+    );
+  }
+}
+
+/// The home screen
+class HomeScreen extends StatelessWidget {
+  /// Constructs a [HomeScreen]
+  const HomeScreen({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(title: const Text('Home Screen')),
+      body: Center(
+        child: ElevatedButton(
+          onPressed: () => context.go('/some-unknown-route'),
+          child: const Text('Simulates user entering unknown url'),
+        ),
+      ),
+    );
+  }
+}
+
+/// The not found screen
+class NotFoundScreen extends StatelessWidget {
+  /// Constructs a [HomeScreen]
+  const NotFoundScreen({super.key, required this.uri});
+
+  /// The uri that can not be found.
+  final String uri;
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(title: const Text('Page Not Found')),
+      body: Center(
+        child: Text("Can't find a page for: $uri"),
+      ),
+    );
+  }
+}