Flutter实现底部导航栏效果

class MyApp extends StatelessWidget {
 // This widget is the root of your application.
 @override
 Widget build(BuildContext context) {
  return new MaterialApp(
   title: 'Flutter Demo',
   theme: new ThemeData(

    primarySwatch: themeColor(),

   ),
   home: new MyHomePage(title: 'Flutter Demo Home Page'),
  );
 }
}

class _MyHomePageState extends State {


 PageController pageController;
 int page = 0;

 @override
 Widget build(BuildContext context) {

  return new Scaffold(

   backgroundColor: Colors.grey,

   body: new PageView(

     children: [
      new Index(),
      new Classify(),
      new Shopping(),
      new Myself()
     ],

     controller: pageController,
     onPageChanged: onPageChanged
   ),

   bottomNavigationBar: new BottomNavigationBar(items: [
    new BottomNavigationBarItem(
     icon: new Icon(Icons.laptop_chromebook),
     title: new Text("主页"),
     backgroundColor: Colors.grey
    ),
    new BottomNavigationBarItem(
      icon: new Icon(Icons.list), title: new Text("分类"),backgroundColor: Colors.grey),
    new BottomNavigationBarItem(
      icon: new Icon(Icons.local_grocery_store), title: new Text("购物车")),
    new BottomNavigationBarItem(icon: new Icon(Icons.person), title: new Text("我的"))
   ],
     onTap: onTap,
     currentIndex: page
   ),
  );
 }

 @override
 void initState() {
  super.initState();
  pageController = new PageController(initialPage: this.page);
 }


 void onTap(int index) {
  pageController.animateToPage(
    index, duration: const Duration(milliseconds: 300),
    curve: Curves.ease);
 }


 void onPageChanged(int page) {
  setState(() {
   this.page = page;
  });
 }


}

import 'package:flutter/material.dart';
class Classify extends StatelessWidget {


 @override
 Widget build(BuildContext context) {
  // TODO: implement build

  return new Scaffold(
   body: new Center(
    child:
    new Text("分类"),
   ),
  );
 }
}