1、BottomNavigationBar

新建组件Tabs.dart

定义StatefulWidget组件Tabs

class Tabs extends StatefulWidget {
  Tabs({Key key}) : super(key: key);
  _TabsState createState() => _TabsState();
}

class _TabsState extends State<Tabs> {
  int _currentIndex=0;
  List _pageList=[
    HomePage(),
    CategoryPage(),
    SettingPage(),
  ];
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("Flutter Demo"),
        ),
        body: this._pageList[this._currentIndex],
        bottomNavigationBar: BottomNavigationBar(
          currentIndex: this._currentIndex,   //配置对应的索引值选中
          onTap: (int index){
              setState(() {  //改变状态
                  this._currentIndex=index;
              });
          },
          iconSize:36.0,      //icon的大小
          fixedColor:Colors.red,  //选中的颜色  
          type:BottomNavigationBarType.fixed,   //配置底部tabs可以有多个按钮
          items: [
            BottomNavigationBarItem(
              icon: Icon(Icons.home),
              title: Text("首页")
            ),
             BottomNavigationBarItem(
              icon: Icon(Icons.category),
              title: Text("分类")
            ),
             BottomNavigationBarItem(
              icon: Icon(Icons.settings),
              title: Text("设置")
            )
          ],
        ),
      );
  }
}