init

client/lib/features/main/screens/main_app_screen.dart

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+import 'package:flutter/material.dart';
+import '../../home/screens/home_screen.dart';
+import '../../learning/screens/learning_home_screen.dart';
+import '../../profile/screens/profile_home_screen.dart';
+
+/// 主应用界面，包含底部导航栏
+class MainAppScreen extends StatefulWidget {
+  const MainAppScreen({super.key});
+
+  @override
+  State<MainAppScreen> createState() => _MainAppScreenState();
+}
+
+class _MainAppScreenState extends State<MainAppScreen> {
+  int _currentIndex = 0;
+
+  final List<Widget> _pages = [
+    const HomeScreen(),
+    const LearningHomeScreen(),
+    const ProfileHomeScreen(),
+  ];
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      body: IndexedStack(
+        index: _currentIndex,
+        children: _pages,
+      ),
+      bottomNavigationBar: Container(
+        decoration: BoxDecoration(
+          color: Colors.white,
+          boxShadow: [
+            BoxShadow(
+              color: Colors.black.withOpacity(0.1),
+              blurRadius: 10,
+              offset: const Offset(0, -2),
+            ),
+          ],
+        ),
+        child: SafeArea(
+          child: Padding(
+            padding: const EdgeInsets.symmetric(horizontal: 8.0, vertical: 8.0),
+            child: Row(
+              mainAxisAlignment: MainAxisAlignment.spaceAround,
+              children: [
+                _buildNavItem(
+                  icon: Icons.home,
+                  label: '首页',
+                  index: 0,
+                ),
+                _buildNavItem(
+                  icon: Icons.school,
+                  label: '学习',
+                  index: 1,
+                ),
+                _buildNavItem(
+                  icon: Icons.person,
+                  label: '我的',
+                  index: 2,
+                ),
+              ],
+            ),
+          ),
+        ),
+      ),
+    );
+  }
+
+  Widget _buildNavItem({
+    required IconData icon,
+    required String label,
+    required int index,
+  }) {
+    final isSelected = _currentIndex == index;
+    final color = isSelected ? const Color(0xFF2196F3) : Colors.grey;
+
+    return GestureDetector(
+      onTap: () {
+        setState(() {
+          _currentIndex = index;
+        });
+      },
+      child: Container(
+        padding: const EdgeInsets.symmetric(vertical: 4, horizontal: 8),
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            Icon(
+              icon,
+              color: color,
+              size: 24,
+            ),
+            const SizedBox(height: 2),
+            Text(
+              label,
+              style: TextStyle(
+                color: color,
+                fontSize: 12,
+                fontWeight: isSelected ? FontWeight.w600 : FontWeight.normal,
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}