flutter底部导航

常规App都有一个底部导航，flutter为我们封装好了底部导航组件

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'flutter的底部导航'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  int _tabIndex = 0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
        centerTitle: true,
      ),
      body: Container(
        child: ListView(
          children: <Widget>[
            Card(
              shape: RoundedRectangleBorder(
                borderRadius: BorderRadiusDirectional.circular(20),
              ),
              clipBehavior: Clip.antiAlias,
              child: Image.asset(
                "images/big.jpg",
                width: double.maxFinite,
              ),
            ),
          ],
        ),
      ),
      bottomNavigationBar: BottomNavigationBar(
        items: <BottomNavigationBarItem>[
          BottomNavigationBarItem(
            icon: Icon(Icons.home),
            title: Text('home'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.school),
            title: Text('school'),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.person),
            title: Text('person'),
          ),
        ],
        type: BottomNavigationBarType.fixed,
        currentIndex: _tabIndex,
        onTap: (index) {
          setState(() {
            _tabIndex = index;
          });
        },
      ),
    );
  }
}