feat:增加底部标题栏

lib/layout/nav_bar.dart

@@ -0,0 +1,22 @@
+import 'package:flutter/material.dart';
+
+import 'menu.dart';
+
+Widget buildBottomNavigationBar({
+  required BuildContext context,
+  required int index,
+  required Function(int) onTap,
+}) {
+  return BottomNavigationBar(
+    currentIndex: index,
+    onTap: onTap,
+    items: bottomNavItems,
+    type: BottomNavigationBarType.fixed,
+    selectedItemColor: Theme.of(context).colorScheme.primary,
+    unselectedItemColor: Colors.grey,
+    showSelectedLabels: true,
+    showUnselectedLabels: true,
+    backgroundColor: Colors.white,
+    elevation: 8,
+  );
+}