20、Scaffold属性 BottomNavigationBar 自定义底部导航

BottomNavigationBar 是底部导航条，可以让我们定义底部Tab切换，bottomNavigationBar是

Scaffold组件的参数。

BottomNavigationBar 常见的属性

BottomNavigationBar 底部菜单选中 

class MyFlutter1 extends StatefulWidget {
  const MyFlutter1({super.key});

  @override
  State<MyFlutter1> createState() => _MyFlutter1State();
}

class _MyFlutter1State extends State<MyFlutter1> {
  int _currentIndex =0;
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text("这是导航栏")),
      bottomNavigationBar: BottomNavigationBar(
       currentIndex: _currentIndex,  //默认选中第几个
       iconSize: 35,
       type:BottomNavigationBarType.fixed, //如果底部有4个或者4个以上的进行选择

       fixedColor: const Color.fromARGB(255, 54, 244, 171), //选中的颜色
       onTap: (index){   //选中变化回调函数
         print("监听$index");
         setState(() {
            _currentIndex = index;
         });
       },
       items: const [
        BottomNavigationBarItem(icon: Icon(Icons.home), label: "首页"),
        BottomNavigationBarItem(icon: Icon(Icons.timeline), label: "时间"),
        BottomNavigationBarItem(icon: Icon(Icons.my_library_add), label: "我的"),
      ]),
      body: const Center(
          child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [],
      )),
    );
  }
}

BottomNavigationBar 底部菜单选中 换页面内容

class MyFlutter1 extends StatefulWidget {
  const MyFlutter1({super.key});

  @override
  State<MyFlutter1> createState() => _MyFlutter1State();
}

class _MyFlutter1State extends State<MyFlutter1> {
  int _currentIndex =0;
  final List<Widget> _pages = [
    const HomePage(),
    const TimePag(),
    const myHome()
    
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text("这是导航栏")),
      bottomNavigationBar: BottomNavigationBar(
       currentIndex: _currentIndex,  //默认选中第几个
       fixedColor: const Color.fromARGB(255, 54, 244, 171), //选中的颜色

        unselectedItemColor: Colors.grey, // 设置未选中按钮的颜色为灰色

 onTap: (index){ //选中变化回调函数 print("监听$index"); setState(() { _currentIndex = index; }); },

        selectedFontSize: 18, // 选中后的文字大小

       items: const [
        BottomNavigationBarItem(icon: Icon(Icons.home), label: "首页"),
        BottomNavigationBarItem(icon: Icon(Icons.timeline), label: "时间"),
        BottomNavigationBarItem(icon: Icon(Icons.my_library_add), label: "我的"),
      ]),
      body: _pages[_currentIndex],
    );
  }
}

 自定义图标

            BottomNavigationBarItem(
                icon: ImageIcon(
                    AssetImage('images/icons/wx_house1.png')), // 非选中状态下的图标
                activeIcon: ImageIcon(
                    AssetImage('images/icons/wx_house2.png')), // 选中状态下的图标
                label: "首页"),