import 'package:flutter/material.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        bottomNavigationBarTheme: BottomNavigationBarThemeData(
          type: BottomNavigationBarType.fixed,
          showSelectedLabels: false,
          showUnselectedLabels: true,
        ),
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _page = 0;

  void _updatePage(int page) {
    setState(() => _page = page);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(child: Text('$_page')),
      bottomNavigationBar: _buildBottomNavBar(),
    );
  }

  Widget _buildBottomNavBar() {
    return BottomNavigationBar(
      onTap: _updatePage,
      currentIndex: _page,
      items: [
        BottomNavigationBarItem(
          icon: const Icon(Icons.looks_one),
          label: 'Label 1',
        ),
        BottomNavigationBarItem(
          icon: const Icon(Icons.looks_two),
          label: 'Label 2',
        ),
        BottomNavigationBarItem(
          icon: const Icon(Icons.looks_3),
          label: 'Label 3',
        ),
      ],
    );
  }
}