Add base skeleton

moneymgr_mobile/lib/widgets/scaffold_with_navigation.dart

@@ -0,0 +1,100 @@
+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+
+/// A scaffold that shows navigation bar/rail when the current path is a navigation
+/// item.
+///
+/// When in a navigation item, a [NavigationBar] will be shown if the width of the
+/// screen is less than 600dp. Otherwise, a [NavigationRail] will be shown.
+class ScaffoldWithNavigation extends StatelessWidget {
+  const ScaffoldWithNavigation({
+    super.key,
+    required this.child,
+    required this.selectedIndex,
+    required this.navigationItems,
+  });
+
+  final Widget child;
+  final int selectedIndex;
+  final List<NavigationItem> navigationItems;
+
+  @override
+  Widget build(BuildContext context) {
+    void onDestinationSelected(int index) =>
+        context.go(navigationItems[index].path);
+
+    // Use navigation rail instead of navigation bar when the screen width is
+    // larger than 600dp.
+    if (MediaQuery.sizeOf(context).width > 600) {
+      return Scaffold(
+        body: Row(
+          children: [
+            NavigationRail(
+              selectedIndex: selectedIndex,
+              onDestinationSelected: onDestinationSelected,
+              destinations: [
+                for (final item in navigationItems)
+                  NavigationRailDestination(
+                    icon: Icon(item.icon),
+                    selectedIcon: item.selectedIcon != null
+                        ? Icon(item.selectedIcon)
+                        : null,
+                    label: Text(item.label),
+                  )
+              ],
+              extended: true,
+            ),
+            Expanded(child: child),
+          ],
+        ),
+      );
+    }
+
+    return Scaffold(
+      body: child,
+      bottomNavigationBar: NavigationBar(
+        selectedIndex: selectedIndex,
+        onDestinationSelected: onDestinationSelected,
+        destinations: [
+          for (final item in navigationItems)
+            NavigationDestination(
+              icon: Icon(item.icon),
+              selectedIcon:
+              item.selectedIcon != null ? Icon(item.selectedIcon) : null,
+              label: item.label,
+            )
+        ],
+      ),
+    );
+  }
+}
+
+/// An item that represents a navigation destination in a navigation bar/rail.
+class NavigationItem {
+  /// Path in the router.
+  final String path;
+
+  /// Widget to show when navigating to this [path].
+  final WidgetBuilder body;
+
+  /// Icon in the navigation bar.
+  final IconData icon;
+
+  /// Icon in the navigation bar when selected.
+  final IconData? selectedIcon;
+
+  /// Label in the navigation bar.
+  final String label;
+
+  /// The subroutes of the route from this [path].
+  final List<RouteBase> routes;
+
+  NavigationItem({
+    required this.path,
+    required this.body,
+    required this.icon,
+    this.selectedIcon,
+    required this.label,
+    this.routes = const [],
+  });
+}