Refactor onboarding to single page

bottom navigation bar

lib/router/scaffold_with_nav_bar.dart

@@ -0,0 +1,65 @@
+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+
+/// Builds the "shell" for the app by building a Scaffold with a
+/// BottomNavigationBar, where [child] is placed in the body of the Scaffold.
+class ScaffoldWithNavBar extends StatelessWidget {
+  /// Constructs an [ScaffoldWithNavBar].
+  const ScaffoldWithNavBar({
+    required this.navigationShell,
+    Key? key,
+  }) : super(key: key ?? const ValueKey<String>('ScaffoldWithNavBar'));
+
+  /// The navigation shell and container for the branch Navigators.
+  final StatefulNavigationShell navigationShell;
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: navigationShell,
+      bottomNavigationBar: BottomNavigationBar(
+        elevation: 0.0,
+        landscapeLayout: BottomNavigationBarLandscapeLayout.centered,
+        selectedFontSize: Theme.of(context).textTheme.labelMedium!.fontSize!,
+        unselectedFontSize: Theme.of(context).textTheme.labelMedium!.fontSize!,
+        // fixedColor: Theme.of(context).colorScheme.primary,
+        // type: BottomNavigationBarType.fixed,
+
+        // Here, the items of BottomNavigationBar are hard coded. In a real
+        // world scenario, the items would most likely be generated from the
+        // branches of the shell route, which can be fetched using
+        // `navigationShell.route.branches`.
+        items: const <BottomNavigationBarItem>[
+          BottomNavigationBarItem(
+            label: 'Home',
+            icon: Icon(Icons.home_outlined),
+            activeIcon: Icon(Icons.home),
+          ),
+          BottomNavigationBarItem(
+            label: 'Settings',
+            icon: Icon(Icons.settings_outlined),
+            activeIcon: Icon(Icons.settings),
+          ),
+        ],
+        currentIndex: navigationShell.currentIndex,
+        onTap: (int index) => _onTap(context, index),
+      ),
+    );
+  }
+
+  /// Navigate to the current location of the branch at the provided index when
+  /// tapping an item in the BottomNavigationBar.
+  void _onTap(BuildContext context, int index) {
+    // When navigating to a new branch, it's recommended to use the goBranch
+    // method, as doing so makes sure the last navigation state of the
+    // Navigator for the branch is restored.
+    navigationShell.goBranch(
+      index,
+      // A common pattern when using bottom navigation bars is to support
+      // navigating to the initial location when tapping the item that is
+      // already active. This example demonstrates how to support this behavior,
+      // using the initialLocation parameter of goBranch.
+      initialLocation: index == navigationShell.currentIndex,
+    );
+  }
+}