import 'package:flutter/material.dart';
import './views/firstPage.dart';
import './views/secondPage.dart';
import './views/thirdPage.dart';
//首先导入三个界面

void main() {
 runApp(new MyApp());
}

class MyApp extends StatefulWidget {
 @override
 _MyHomePageState createState() => new _MyHomePageState();
}

class _MyHomePageState extends State with TickerProviderStateMixin{

 int _tabIndex = 0;

 List _navigationViews;

 var appBarTitles = ['首页', '发现', '我的'];

 PageController pageController;

 var _body;

 initData() {
  _body = new IndexedStack(
   children: [new FirstPage(), new SecondPage(), new ThirdPage()],
   index: _tabIndex,
  );
 }

 @override
 void initState() {
  super.initState();
  _navigationViews = [
   new BottomNavigationBarItem(
    icon: const Icon(Icons.home),
    title: new Text(appBarTitles[0]),
    backgroundColor: Colors.blue,
   ),
   new BottomNavigationBarItem(
    icon: const Icon(Icons.widgets),
    title: new Text(appBarTitles[1]),
    backgroundColor: Colors.blue,
   ),
   new BottomNavigationBarItem(
    icon: const Icon(Icons.person),
    title: new Text(appBarTitles[2]),
    backgroundColor: Colors.blue,
   ),
  ];
 }

 final navigatorKey = GlobalKey();
 @override
 Widget build(BuildContext context) {

  initData();

  return new MaterialApp(
   navigatorKey: navigatorKey,
   theme: new ThemeData(
     primaryColor: Colors.blue,
     accentColor: Colors.blue
   ),
   home: new Scaffold(
    appBar: new AppBar(
     title: new Text(
      appBarTitles[_tabIndex],
      style: new TextStyle(color: Colors.white),
     ),
    ),
    body: _body,
    bottomNavigationBar: new BottomNavigationBar(
     items: _navigationViews
       .map((BottomNavigationBarItem navigationView) => navigationView)
       .toList(),
     currentIndex: _tabIndex,
     type: BottomNavigationBarType.fixed,
     onTap: (index) {
      setState(() {
       _tabIndex = index;
      });
     },
    ),
   ),
  );
 }
}

import 'package:flutter/material.dart';

class FirstPage extends StatefulWidget {
 @override
 State createState() => new FirstPageState();

}

class FirstPageState extends State {
 @override
 Widget build(BuildContext context) {
  return new Scaffold(
   body: new Center(
    child: new Text('这是第一个界面'),
   ),
  );
 }

}

import 'package:flutter/material.dart';

class SecondPage extends StatefulWidget {
 @override
 State createState() => SecondPageState();

}

class SecondPageState extends State {
 @override
 Widget build(BuildContext context) {
  return new Scaffold(
   body: new Center(
    child: new Text("这是我第二个页面"),
   ),
  );
 }
}

import 'package:flutter/material.dart';

class ThirdPage extends StatefulWidget {
 @override
 State createState() => ThirdPageState();

}

class ThirdPageState extends State{
 @override
 Widget build(BuildContext context) {
  return new Scaffold(
   body: new Center(
    child: new Text('我是界面三'),
   ),
  );
 }
}