main.dart

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

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: "Flutter bottomNavigationBar",
      home: BottomNavigationWidget(),
    );
  }
}

bottom_navigation_widget.dart

import 'package:flutter/material.dart';
import 'pages/home_screen.dart';
import 'pages/email_screen.dart';
import 'pages/pages_screen.dart';
import 'pages/airplay_screen.dart';
import 'pages/my_screen.dart';

class BottomNavigationWidget extends StatefulWidget {
  @override
  _BottomNavigationWidgetState createState() => _BottomNavigationWidgetState();
}

class _BottomNavigationWidgetState extends State<BottomNavigationWidget> {
  
  int _currentIndex = 0;
  List<Widget> list = List();

  @override
  void initState(){
    list
      ..add(HomeScreen())
      ..add(EmailScreen())
      ..add(PagesScreen())
      ..add(AirplayScreen())
      ..add(MyScreen());
    super.initState();
  }
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body:list[_currentIndex],
      bottomNavigationBar: BottomNavigationBar(
        type: BottomNavigationBarType.fixed,
        items: [
          BottomNavigationBarItem(
            icon: Icon(
              Icons.home,
            ),
            title: Text(
              'Home',
            )
          ),
          BottomNavigationBarItem(
            icon: Icon(
              Icons.email,
            ),
            title: Text(
              'Email',
            )
          ),
          BottomNavigationBarItem(
            icon: Icon(
              Icons.pages,
            ),
            title: Text(
              'Pages',
            )
          ),
          BottomNavigationBarItem(
            icon: Icon(
              Icons.airplay,
            ),
            title: Text(
              'Airplay',
            )
          ),
          BottomNavigationBarItem(
            icon: Icon(
              Icons.people,
            ),
            title: Text(
              'My',
            )
          ),
        ],
        currentIndex: _currentIndex,
        onTap: (int index){
          setState(() {
            _currentIndex = index;
          });
        },
      ),
    );
  }
}

home_screen

这个作为底部的页面可以复制用

import 'package:flutter/material.dart';

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