Flutter实现底部导航栏

import 'package:flutter/material.dart';
import 'package:flutter_guohe/pages/main.dart';
 
void main() {
 runApp(new Guohe());
}

class Guohe extends StatefulWidget {
 @override
 GuoheState createState() =  new GuoheState();
}
 
class GuoheState extends State<Guohe  {
 @override
 Widget build(BuildContext context) {
 
 }
}

import 'package:flutter/material.dart';
 
class Playground extends StatefulWidget {
 @override
 PlaygroundState createState() =  new PlaygroundState();
}
 
class PlaygroundState extends State<Playground  {
 @override
 Widget build(BuildContext context) {
 return new MaterialApp(
  home: new Scaffold(
  appBar: new AppBar(
   title: new Text("操场"),
   backgroundColor: Color.fromARGB(255, 119, 136, 213), //设置appbar背景颜色
   centerTitle: true, //设置标题是否局中
  ),
  body: new Center(
   child: new Text('操场'),
  ),
  ),
 );
 }
}

/**
 * APP的主入口文件
 */
 
import 'package:flutter/material.dart';
 
import 'package:flutter_guohe/pages/main/today.dart';
import 'package:flutter_guohe/pages/main/playground.dart';
import 'package:flutter_guohe/pages/main/kb.dart';
import 'package:flutter_guohe/pages/main/leftmenu.dart';
 
import 'package:flutter_guohe/common/eventBus.dart';
 
//果核的主界面
class Guohe extends StatefulWidget {
 @override
 GuoheState createState() =  new GuoheState();
}
 
class GuoheState extends State<Guohe  with SingleTickerProviderStateMixin {
 TabController controller;
 
 @override
 void initState() {
 controller = new TabController(length: 3, vsync: this);
 }
 
 @override
 void dispose() {
 controller.dispose();
 super.dispose();
 }
 
 @override
 Widget build(BuildContext context) {
 return new MaterialApp(
  home: new Scaffold(
  drawer: new LeftMenu(),
  body: new TabBarView(
   controller: controller,
   children: <Widget [
   new Today(),
   new Kb(),
   new Playground(),
   ],
  ),
  bottomNavigationBar: new Material(
   color: Colors.white,
   child: new TabBar(
   controller: controller,
   labelColor: Colors.deepPurpleAccent,
   unselectedLabelColor: Colors.black26,
   tabs: <Widget [
    new Tab(
    text: "今日",
    icon: new Icon(Icons.brightness_5),
    ),
    new Tab(
    text: "课表",
    icon: new Icon(Icons.map),
    ),
    new Tab(
    text: "操场",
    icon: new Icon(Icons.directions_run),
    ),
   ],
   ),
  ),
  ),
 );
 }
}

labelColor: Colors.deepPurpleAccent,
unselectedLabelColor: Colors.black26,