Flutter中底部导航栏具体实现方式

老规格，先看图：

程序主结构如下：

1.在程序主入口文件main.dart添加如下代码

import 'package:flutter/material.dart';
import 'bottom_navigation.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData.light(),
      home: BottomNavigationWidget(),
    );
  }
}

2.创建4个界面，home_page.dart、constant_page.dart、find_page.dart、my_page.dart

home_page.dart

import 'package:flutter/material.dart';

class HomePage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('HomePage'),),
      body: Center(
        child: Text('这是首页'),
      ),
    );
  }
}

constant_page.dart

import 'package:flutter/material.dart';

class ConstantPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('ConstantPage'),),
      body: Center(
        child: Text('这是联系人'),
      ),
    );
  }
}

find_page.dart

import 'package:flutter/material.dart';

class FindPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('FindPage'),),
      body: Center(
        child: Text('这是发现'),
      ),
    );
  }
}

my_page.dart

import 'package:flutter/material.dart';

class MyPage extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('MyPage'),),
      body: Center(
        child: Text('这是我的'),
      ),
    );
  }
}

3.创建动态组件BottomNavigationWidget，新建bottom_navigation.dart

import 'package:flutter/material.dart';
import 'pages/home_page.dart';
import 'pages/constant_page.dart';
import 'pages/find_page.dart';
import 'pages/my_page.dart';

class BottomNavigationWidget extends StatefulWidget {

  @override
  _BottomNavigationWidgetState createState() => new _BottomNavigationWidgetState();
}

class _BottomNavigationWidgetState extends State<BottomNavigationWidget> {
  final List<Widget> list = List();
  int _currentIndex = 0;
  @override
  void initState() {
    list
      ..add(HomePage())
      ..add(ConstantPage())
      ..add(FindPage())
      ..add(MyPage());
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: list[_currentIndex],
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: _currentIndex,
          onTap: (int index){
            setState(() {
              _currentIndex = index;
            });
          },
          type: BottomNavigationBarType.fixed,
          items: [
            BottomNavigationBarItem(
              icon: Icon(Icons.home,color: Colors.blue,),
              title: Text('首页',style: TextStyle(color: Colors.blue))
            ),
            BottomNavigationBarItem(
                icon: Icon(Icons.contacts,color: Colors.blue,),
                title: Text('联系',style: TextStyle(color: Colors.blue))
            ),
            BottomNavigationBarItem(
                icon: Icon(Icons.find_in_page,color: Colors.blue,),
                title: Text('发现',style: TextStyle(color: Colors.blue))
            ),
            BottomNavigationBarItem(
                icon: Icon(Icons.menu,color: Colors.blue,),
                title: Text('我的',style: TextStyle(color: Colors.blue))
            ),

          ]
      ),
    );
  }
}