[移动开发]flutter- 底部导航

示例：

import 'package:flutter/material.dart';


class Home extends StatefulWidget {
  Home({Key key}) : super(key: key);

  @override
  _HomeState createState() => _HomeState();
}

class _HomeState extends State<Home> {

  final List<BottomNavigationBarItem> bottomNavigationItems = [
    BottomNavigationBarItem(
      icon: Icon(Icons.home),
      backgroundColor: Colors.blue,
      label: '首页',
    ),
     BottomNavigationBarItem(
      icon: Icon(Icons.calendar_view_day_sharp),
      backgroundColor: Colors.yellow,
      label: '分类',
    ),
     BottomNavigationBarItem(
      icon: Icon(Icons.shopping_cart),
      backgroundColor: Colors.cyan,
      label: '购物车',
    ),
     BottomNavigationBarItem(
      icon: Icon(Icons.person),
      backgroundColor: Colors.purple,
      label: '我的',
    )
  ];

  final page = [
    Center(child: Text('首页', style: TextStyle(fontSize: 50))),
    Center(child: Text('分类', style: TextStyle(fontSize: 50))),
    Center(child: Text('购物车', style: TextStyle(fontSize: 50))),
    Center(child: Text('我的', style: TextStyle(fontSize: 50)))
  ];

  int index;

  void changePage(currentIndex) {
    setState(() {
      index = currentIndex;      
    });
  }

  @override
    void initState() {
      // TODO: implement initState
      super.initState();
      index = 0;
    }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Tabbar'),
      ),
      bottomNavigationBar: BottomNavigationBar(
        items: bottomNavigationItems, 
        currentIndex: index,
        type: BottomNavigationBarType.shifting,
        onTap: (index) {
          changePage(index);
        },
      ),
      body: page[index],
    );
  }
}