[go_router] Fixed TabView swiping in custom stateful shell route exam…

…ple (#7583) Updated `custom_stateful_shell_route.dart` example to better support swiping in TabView. Also added code to demonstrate use of PageView instead of TabView. Note that to be fully effective from a usability perspective, the PR #6467 (branch preloading) need also be merged. This PR addresses: * flutter/flutter#150837 * flutter/flutter#112267 ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] page, which explains my responsibilities. - [x] I read and followed the [relevant style guides] and ran the auto-formatter. (Unlike the flutter/flutter repo, the flutter/packages repo does use `dart format`.) - [x] I signed the [CLA]. - [x] The title of the PR starts with the name of the package surrounded by square brackets, e.g. `[shared_preferences]` - [x] I [linked to at least one issue that this PR fixes] in the description above. - [x] I updated `pubspec.yaml` with an appropriate new version according to the [pub versioning philosophy], or this PR is [exempt from version changes]. - [x] I updated `CHANGELOG.md` to add a description of the change, [following repository CHANGELOG style], or this PR is [exempt from CHANGELOG changes]. - [x] I updated/added relevant documentation (doc comments with `///`). - [x] I added new tests to check the change I am making, or this PR is [test-exempt]. - [x] All existing and new tests are passing. If you need help, consider asking for advice on the #hackers-new channel on [Discord].  [Contributor Guide]: https://github.com/flutter/packages/blob/main/CONTRIBUTING.md [Tree Hygiene]: https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md [relevant style guides]: https://github.com/flutter/packages/blob/main/CONTRIBUTING.md#style [CLA]: https://cla.developers.google.com/ [Discord]: https://github.com/flutter/flutter/blob/master/docs/contributing/Chat.md [linked to at least one issue that this PR fixes]: https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#overview [pub versioning philosophy]: https://dart.dev/tools/pub/versioning [exempt from version changes]: https://github.com/flutter/flutter/blob/master/docs/ecosystem/contributing/README.md#version [following repository CHANGELOG style]: https://github.com/flutter/flutter/blob/master/docs/ecosystem/contributing/README.md#changelog-style [exempt from CHANGELOG changes]: https://github.com/flutter/flutter/blob/master/docs/ecosystem/contributing/README.md#changelog [test-exempt]: https://github.com/flutter/flutter/blob/master/docs/contributing/Tree-hygiene.md#tests
flutter · Sep 24, 2024 · 47795ab · 47795ab
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diff --git a/packages/go_router/CHANGELOG.md b/packages/go_router/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 14.2.8
+
+- Updated custom_stateful_shell_route example to better support swiping in TabView as well as demonstration of the use of PageView. 
+
 ## 14.2.7
 
 - Fixes issue so that the parseRouteInformationWithContext can handle non-http Uris.

diff --git a/packages/go_router/example/lib/others/custom_stateful_shell_route.dart b/packages/go_router/example/lib/others/custom_stateful_shell_route.dart
@@ -3,13 +3,18 @@
 // found in the LICENSE file.
 
 import 'package:collection/collection.dart';
+import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 import 'package:go_router/go_router.dart';
 
 final GlobalKey<NavigatorState> _rootNavigatorKey =
     GlobalKey<NavigatorState>(debugLabel: 'root');
 final GlobalKey<NavigatorState> _tabANavigatorKey =
     GlobalKey<NavigatorState>(debugLabel: 'tabANav');
+@visibleForTesting
+// ignore: public_member_api_docs
+final GlobalKey<TabbedRootScreenState> tabbedRootScreenKey =
+    GlobalKey<TabbedRootScreenState>(debugLabel: 'TabbedRootScreen');
 
 // This example demonstrates how to setup nested navigation using a
 // BottomNavigationBar, where each bar item uses its own persistent navigator,
@@ -52,6 +57,8 @@ class NestedTabNavigationExampleApp extends StatelessWidget {
           // are managed (using AnimatedBranchContainer).
           return ScaffoldWithNavBar(
               navigationShell: navigationShell, children: children);
+          // NOTE: To use a Cupertino version of ScaffoldWithNavBar, replace
+          // ScaffoldWithNavBar above with CupertinoScaffoldWithNavBar.
         },
         branches: <StatefulShellBranch>[
           // The route branch for the first tab of the bottom navigation bar.
@@ -78,13 +85,13 @@ class NestedTabNavigationExampleApp extends StatelessWidget {
             ],
           ),
 
-          // The route branch for the third tab of the bottom navigation bar.
+          // The route branch for the second tab of the bottom navigation bar.
           StatefulShellBranch(
             // StatefulShellBranch will automatically use the first descendant
             // GoRoute as the initial location of the branch. If another route
             // is desired, specify the location of it using the defaultLocation
             // parameter.
-            // defaultLocation: '/c2',
+            // defaultLocation: '/b2',
             routes: <RouteBase>[
               StatefulShellRoute(
                 builder: (BuildContext context, GoRouterState state,
@@ -102,7 +109,12 @@ class NestedTabNavigationExampleApp extends StatelessWidget {
                   // See TabbedRootScreen for more details on how the children
                   // are managed (in a TabBarView).
                   return TabbedRootScreen(
-                      navigationShell: navigationShell, children: children);
+                    navigationShell: navigationShell,
+                    key: tabbedRootScreenKey,
+                    children: children,
+                  );
+                  // NOTE: To use a PageView version of TabbedRootScreen,
+                  // replace TabbedRootScreen above with PagedRootScreen.
                 },
                 // This bottom tab uses a nested shell, wrapping sub routes in a
                 // top TabBar.
@@ -222,6 +234,70 @@ class ScaffoldWithNavBar extends StatelessWidget {
   }
 }
 
+/// Alternative version of [ScaffoldWithNavBar], using a [CupertinoTabScaffold].
+// ignore: unused_element, unreachable_from_main
+class CupertinoScaffoldWithNavBar extends StatefulWidget {
+  /// Constructs an [ScaffoldWithNavBar].
+  // ignore: unreachable_from_main
+  const CupertinoScaffoldWithNavBar({
+    required this.navigationShell,
+    required this.children,
+    Key? key,
+  }) : super(key: key ?? const ValueKey<String>('ScaffoldWithNavBar'));
+
+  /// The navigation shell and container for the branch Navigators.
+  // ignore: unreachable_from_main
+  final StatefulNavigationShell navigationShell;
+
+  /// The children (branch Navigators) to display in a custom container
+  /// ([AnimatedBranchContainer]).
+  // ignore: unreachable_from_main
+  final List<Widget> children;
+
+  @override
+  State<StatefulWidget> createState() => _CupertinoScaffoldWithNavBarState();
+}
+
+class _CupertinoScaffoldWithNavBarState
+    extends State<CupertinoScaffoldWithNavBar> {
+  late final CupertinoTabController tabController =
+      CupertinoTabController(initialIndex: widget.navigationShell.currentIndex);
+
+  @override
+  void dispose() {
+    tabController.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return CupertinoTabScaffold(
+      controller: tabController,
+      tabBar: CupertinoTabBar(
+        items: const <BottomNavigationBarItem>[
+          BottomNavigationBarItem(icon: Icon(Icons.home), label: 'Section A'),
+          BottomNavigationBarItem(icon: Icon(Icons.work), label: 'Section B'),
+        ],
+        currentIndex: widget.navigationShell.currentIndex,
+        onTap: (int index) => _onTap(context, index),
+      ),
+      // Note: It is common to use CupertinoTabView for the tabBuilder when
+      // using CupertinoTabScaffold and CupertinoTabBar. This would however be
+      // redundant when using StatefulShellRoute, since a separate Navigator is
+      // already created for each branch, meaning we can simply use the branch
+      // Navigator Widgets (i.e. widget.children) directly.
+      tabBuilder: (BuildContext context, int index) => widget.children[index],
+    );
+  }
+
+  void _onTap(BuildContext context, int index) {
+    widget.navigationShell.goBranch(
+      index,
+      initialLocation: index == widget.navigationShell.currentIndex,
+    );
+  }
+}
+
 /// Custom branch Navigator container that provides animated transitions
 /// when switching branches.
 class AnimatedBranchContainer extends StatelessWidget {
@@ -271,7 +347,7 @@ class RootScreenA extends StatelessWidget {
   Widget build(BuildContext context) {
     return Scaffold(
       appBar: AppBar(
-        title: const Text('Root of section A'),
+        title: const Text('Section A root'),
       ),
       body: Center(
         child: Column(
@@ -386,20 +462,43 @@ class TabbedRootScreen extends StatefulWidget {
   final List<Widget> children;
 
   @override
-  State<StatefulWidget> createState() => _TabbedRootScreenState();
+  State<StatefulWidget> createState() => TabbedRootScreenState();
 }
 
-class _TabbedRootScreenState extends State<TabbedRootScreen>
+@visibleForTesting
+// ignore: public_member_api_docs
+class TabbedRootScreenState extends State<TabbedRootScreen>
     with SingleTickerProviderStateMixin {
-  late final TabController _tabController = TabController(
+  @visibleForTesting
+  // ignore: public_member_api_docs
+  late final TabController tabController = TabController(
       length: widget.children.length,
       vsync: this,
       initialIndex: widget.navigationShell.currentIndex);
 
+  void _switchedTab() {
+    if (tabController.index != widget.navigationShell.currentIndex) {
+      widget.navigationShell.goBranch(tabController.index);
+    }
+  }
+
+  @override
+  void initState() {
+    super.initState();
+    tabController.addListener(_switchedTab);
+  }
+
+  @override
+  void dispose() {
+    tabController.removeListener(_switchedTab);
+    tabController.dispose();
+    super.dispose();
+  }
+
   @override
   void didUpdateWidget(covariant TabbedRootScreen oldWidget) {
     super.didUpdateWidget(oldWidget);
-    _tabController.index = widget.navigationShell.currentIndex;
+    tabController.index = widget.navigationShell.currentIndex;
   }
 
   @override
@@ -410,14 +509,15 @@ class _TabbedRootScreenState extends State<TabbedRootScreen>
 
     return Scaffold(
       appBar: AppBar(
-          title: const Text('Root of Section B (nested TabBar shell)'),
+          title: Text(
+              'Section B root (tab: ${widget.navigationShell.currentIndex + 1})'),
           bottom: TabBar(
-            controller: _tabController,
+            controller: tabController,
             tabs: tabs,
             onTap: (int tappedIndex) => _onTabTap(context, tappedIndex),
           )),
       body: TabBarView(
-        controller: _tabController,
+        controller: tabController,
         children: widget.children,
       ),
     );
@@ -428,6 +528,84 @@ class _TabbedRootScreenState extends State<TabbedRootScreen>
   }
 }
 
+/// Alternative implementation of TabbedRootScreen, demonstrating the use of
+/// a [PageView].
+// ignore: unreachable_from_main
+class PagedRootScreen extends StatefulWidget {
+  /// Constructs a PagedRootScreen
+  // ignore: unreachable_from_main
+  const PagedRootScreen(
+      {required this.navigationShell, required this.children, super.key});
+
+  /// The current state of the parent StatefulShellRoute.
+  // ignore: unreachable_from_main
+  final StatefulNavigationShell navigationShell;
+
+  /// The children (branch Navigators) to display in the [TabBarView].
+  // ignore: unreachable_from_main
+  final List<Widget> children;
+
+  @override
+  State<StatefulWidget> createState() => _PagedRootScreenState();
+}
+
+/// Alternative implementation _TabbedRootScreenState, demonstrating the use of
+/// a PageView.
+class _PagedRootScreenState extends State<PagedRootScreen> {
+  late final PageController _pageController = PageController(
+    initialPage: widget.navigationShell.currentIndex,
+  );
+
+  @override
+  void dispose() {
+    _pageController.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text(
+            'Section B root (tab ${widget.navigationShell.currentIndex + 1})'),
+      ),
+      body: Column(
+        children: <Widget>[
+          Row(
+              mainAxisAlignment: MainAxisAlignment.spaceEvenly,
+              children: <Widget>[
+                ElevatedButton(
+                  onPressed: () => _animateToPage(0),
+                  child: const Text('Tab 1'),
+                ),
+                ElevatedButton(
+                  onPressed: () => _animateToPage(1),
+                  child: const Text('Tab 2'),
+                ),
+              ]),
+          Expanded(
+            child: PageView(
+              onPageChanged: (int i) => widget.navigationShell.goBranch(i),
+              controller: _pageController,
+              children: widget.children,
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+
+  void _animateToPage(int index) {
+    if (_pageController.hasClients) {
+      _pageController.animateToPage(
+        index,
+        duration: const Duration(milliseconds: 500),
+        curve: Curves.bounceOut,
+      );
+    }
+  }
+}
+
 /// Widget for the pages in the top tab bar.
 class TabScreen extends StatelessWidget {
   /// Creates a RootScreen

diff --git a/packages/go_router/example/test/custom_stateful_shell_route_test.dart b/packages/go_router/example/test/custom_stateful_shell_route_test.dart
@@ -0,0 +1,32 @@
+// 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:flutter_test/flutter_test.dart';
+import 'package:go_router_examples/others/custom_stateful_shell_route.dart';
+
+void main() {
+  testWidgets(
+      'Changing active tab in TabController of TabbedRootScreen (root screen '
+      'of branch/section B) correctly navigates to appropriate screen',
+      (WidgetTester tester) async {
+    await tester.pumpWidget(NestedTabNavigationExampleApp());
+    expect(find.text('Screen A'), findsOneWidget);
+
+    // navigate to ScreenB
+    await tester.tap(find.text('Section B'));
+    await tester.pumpAndSettle();
+    expect(find.text('Screen B1'), findsOneWidget);
+
+    // Get TabController from TabbedRootScreen (root screen of branch/section B)
+    final TabController? tabController =
+        tabbedRootScreenKey.currentState?.tabController;
+    expect(tabController, isNotNull);
+
+    // Simulate swiping TabView to change active tab in TabController
+    tabbedRootScreenKey.currentState?.tabController.index = 1;
+    await tester.pumpAndSettle();
+    expect(find.text('Screen B2'), findsOneWidget);
+  });
+}
diff --git a/packages/go_router/pubspec.yaml b/packages/go_router/pubspec.yaml
@@ -1,7 +1,7 @@
 name: go_router
 description: A declarative router for Flutter based on Navigation 2 supporting
   deep linking, data-driven routes and more
-version: 14.2.7
+version: 14.2.8
 repository: https://github.com/flutter/packages/tree/main/packages/go_router
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+go_router%22