Flutter实现底部菜单导航

return new MaterialApp(
  home: new Scaffold(
   body: new Center(
    child: _currentPage // 动态的展示我们当前的页面
   ),
   bottomNavigationBar: bottomNavigationBar, // 底部工具栏
  ),

  theme: new ThemeData(
  primarySwatch: Colors.blue, // 设置主题颜色
  ),

 );

import 'package:flutter/material.dart';
import 'package:flutter_demo/index/index.dart';   // 导入index.dart

// 这里为入口函数
void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
 // This widget is the root of your application.
 @override
 Widget build(BuildContext context) {
 return new MaterialApp(
  title: 'Flutter Demo',
  home: new Index(),  // 指定去加载 Index页面。
 );
 }
}

import 'package:flutter/material.dart';

// 创建一个 Icon 展示控件
class NavigationIconView {

 // 创建两个属性，一个是 用来展示 icon， 一个是动画处理
 final BottomNavigationBarItem item;
 final AnimationController controller;

 // 类似于 java 中的构造方法
 // 创建 NavigationIconView 需要传入三个参数， icon 图标，title 标题， TickerProvider
 NavigationIconView({Widget icon, Widget title, TickerProvider vsync}):
 item = new BottomNavigationBarItem(
  icon: icon,
  title: title,
 ),
 controller = new AnimationController(
  duration: kThemeAnimationDuration, // 设置动画持续的时间
  vsync: vsync       // 默认属性和参数
 );
}

import 'package:flutter/material.dart';
import 'package:flutter_demo/NoticePage/notice_page.dart';
import 'package:flutter_demo/home/home_page.dart';
import 'package:flutter_demo/idea/idea_page.dart';
import 'package:flutter_demo/market/market_page.dart';
import 'package:flutter_demo/my/my_page.dart';

import 'navigation_icon_view.dart'; // 如果是在同一个包的路径下，可以直接使用对应的文件名

// 创建一个 带有状态的 Widget Index
class Index extends StatefulWidget {

 // 固定的写法
 @override
 State<StatefulWidget> createState() => new _IndexState();
}

// 要让主页面 Index 支持动效，要在它的定义中附加mixin类型的对象TickerProviderStateMixin
class _IndexState extends State<Index> with TickerProviderStateMixin{

 int _currentIndex = 0; // 当前界面的索引值
 List<NavigationIconView> _navigationViews; // 底部图标按钮区域
 List<StatefulWidget> _pageList; // 用来存放我们的图标对应的页面
 StatefulWidget _currentPage; // 当前的显示页面

 // 定义一个空的设置状态值的方法
 void _rebuild() {
 setState((){});
 }

 @override
 void initState() {
 super.initState();

 // 初始化导航图标
 _navigationViews = <NavigationIconView>[
  new NavigationIconView(icon: new Icon(Icons.assessment), title: new Text("首页"), vsync: this), // vsync 默认属性和参数
  new NavigationIconView(icon: new Icon(Icons.all_inclusive), title: new Text("想法"), vsync: this),
  new NavigationIconView(icon: new Icon(Icons.add_shopping_cart), title: new Text("市场"), vsync: this),
  new NavigationIconView(icon: new Icon(Icons.add_alert), title: new Text("通知"), vsync: this),
  new NavigationIconView(icon: new Icon(Icons.perm_identity), title: new Text("我的"), vsync: this),
 ];

 // 给每一个按钮区域加上监听
 for (NavigationIconView view in _navigationViews) {
  view.controller.addListener(_rebuild);
 }

 // 将我们 bottomBar 上面的按钮图标对应的页面存放起来，方便我们在点击的时候
 _pageList = <StatefulWidget>[
  new HomePage(),
  new IdeaPage(),
  new MarketPage(),
  new NoticePage(),
  new MyPage()
 ];
 _currentPage = _pageList[_currentIndex];
 }

 @override
 Widget build(BuildContext context) {

 // 声明定义一个 底部导航的工具栏
 final BottomNavigationBar bottomNavigationBar = new BottomNavigationBar(
  items: _navigationViews
   .map((NavigationIconView navigationIconView) => navigationIconView.item)
   .toList(), // 添加 icon 按钮
  currentIndex: _currentIndex, // 当前点击的索引值
  type: BottomNavigationBarType.fixed, // 设置底部导航工具栏的类型：fixed 固定
  onTap: (int index){ // 添加点击事件
  setState((){ // 点击之后，需要触发的逻辑事件
   _navigationViews[_currentIndex].controller.reverse();
   _currentIndex = index;
   _navigationViews[_currentIndex].controller.forward();
   _currentPage = _pageList[_currentIndex];
  });
  },
 );

 return new MaterialApp(
  home: new Scaffold(
   body: new Center(
    child: _currentPage // 动态的展示我们当前的页面
   ),
   bottomNavigationBar: bottomNavigationBar, // 底部工具栏
  ),

  theme: new ThemeData(
  primarySwatch: Colors.blue, // 设置主题颜色
  ),

 );
 }

}

import 'package:flutter/material.dart';

class HomePage extends StatefulWidget{
 @override
 State<StatefulWidget> createState() => new _HomePageState();
}

class _HomePageState extends State<HomePage> {

 @override
 Widget build(BuildContext context) {
 return new MaterialApp(
  home: new Scaffold(
  appBar: new AppBar(
   title: new Text('首页'),
   actions: <Widget>[
   new Container()
   ],
  ),
  body: new Center(
   child: null,
  ),
  ),
 );
 }
}

import 'package:flutter/material.dart';

class IdeaPage extends StatefulWidget{
 @override
 State<StatefulWidget> createState() => new _IdeaPageState();
}
class _IdeaPageState extends State<IdeaPage> {

 @override
 Widget build(BuildContext context) {
 return new MaterialApp(
  home: new Scaffold(
  appBar: new AppBar(
   title: new Text('想法'),
   actions: <Widget>[
   new Container()
   ],
  ),
  body: new Center(
   child: null,
  ),
  ),
 );
 }
}

import 'package:flutter/material.dart';
class MarketPage extends StatefulWidget{
 @override
 State<StatefulWidget> createState() => new _MarketPageState();
}
class _MarketPageState extends State<MarketPage> {
 @override
 Widget build(BuildContext context) {
 return new MaterialApp(
  home: new Scaffold(
  appBar: new AppBar(
   title: new Text('市场'),
   // 后面的省略
   // ......
  )
  ),
 );
 }

}