add go_relative example for go_router

packages/go_router/example/lib/go_relative.dart

@@ -0,0 +1,120 @@
+// 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 demonstrates how to use GoRoute.goRelative.
+void main() => runApp(const MyApp());
+
+/// The route configuration.
+final GoRouter _router = GoRouter(
+  routes: <RouteBase>[
+    GoRoute(
+      path: '/',
+      builder: (BuildContext context, GoRouterState state) {
+        return const HomeScreen();
+      },
+      routes: <RouteBase>[
+        GoRoute(
+          path: 'details',
+          builder: (BuildContext context, GoRouterState state) {
+            return const DetailsScreen();
+          },
+          routes: <RouteBase>[
+            GoRoute(
+              path: 'settings',
+              builder: (BuildContext context, GoRouterState state) {
+                return const SettingsScreen();
+              },
+            ),
+          ],
+        ),
+      ],
+    ),
+  ],
+);
+
+/// 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: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: <Widget>[
+            ElevatedButton(
+              onPressed: () => context.goRelative('details'),
+              child: const Text('Go to the Details screen'),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+/// The details screen
+class DetailsScreen extends StatelessWidget {
+  /// Constructs a [DetailsScreen]
+  const DetailsScreen({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(title: const Text('Details Screen')),
+      body: Center(
+          child: Column(
+        children: <Widget>[
+          TextButton(
+            onPressed: () {
+              context.pop();
+            },
+            child: const Text('go back'),
+          ),
+          TextButton(
+            onPressed: () {
+              context.goRelative('settings');
+            },
+            child: const Text('go to settings'),
+          ),
+        ],
+      )),
+    );
+  }
+}
+
+/// The settings screen
+class SettingsScreen extends StatelessWidget {
+  /// Constructs a [SettingsScreen]
+  const SettingsScreen({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(title: const Text('Settings Screen')),
+      body: const Center(
+        child: Text('Settings'),
+      ),
+    );
+  }
+}