在 Flutter 中使用 NavigationRail 和 BottomNavigationBar 创建自适应布局

import 'package:flutter/material.dart';
 
void main() => runApp(MyApp());
 
class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      home: HomePage(),
    );
  }
}
 
class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}
 
class _HomePageState extends State<HomePage> {
  int _selectedIndex = 0;
 
  void _onItemTapped(int index) {
    setState(() {
      _selectedIndex = index;
    });
  }
 
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: _getBody(_selectedIndex),
      bottomNavigationBar: BottomNavigationBar(
        items: <BottomNavigationBarItem>[
          BottomNavigationBarItem(icon: Icon(Icons.home), title: Text('Home')),
          BottomNavigationBarItem(icon: Icon(Icons.settings), title: Text('Settings')),
        ],
        currentIndex: _selectedIndex,
        selectedItemColor: Colors.blue,
        onTap: _onItemTapped,
      ),
      navigationRail: NavigationRail(
        selectedIndex: _selectedIndex,
        onDestinationSelected: _onItemTapped,
        destinations: [
          NavigationRailDestination(icon: Icon(Icons.home), label: Text('Home')),
          NavigationRailDestination(icon: Icon(Icons.settings), label: Text('Settings')),
        ],
      ),
    );
  }
 
  Widget _getBody(int index) {
    switch (index) {
      case 0:
        return Text('Home Screen');
      case 1:
        return Text('Settings Screen');
      default:
        return Text('Unknown screen');
    }
  }
}

这段代码展示了如何在Flutter中同时使用NavigationRail和BottomNavigationBar来创建一个具有导航功能的应用程序。当用户点击底部导航栏或侧边导航栏中的项目时，应用程序会更新当前显示的页面。这种方法可以使应用程序在不同的屏幕尺寸上保持响应式布局。