Flutter Doc JPのBottomNavigationBarで軽く詰まったので

備忘録
Flutter初心者
Flutter Doc JPのBottomNavigationBarで軽く詰まったので

ここが抜けてたら、初心者はわからへん
MainPageがウィジェットじゃないからって怒られる。
　　　　　　　　↓
MainPageのStatefullWidget作る
↓
class MyAppのhome にMainPage(),追加

main.dart

import 'package:flutter/material.dart';

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

  class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MainPage(),
     );
    }
  }

  class MainPage extends StatefulWidget{
    @override
    _MainPageState createState () => _MainPageState();
  }

以下全文

main.dart

import 'package:flutter/material.dart';

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

  class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MainPage(),
     );
    }
  }

  class MainPage extends StatefulWidget{
    @override
    _MainPageState createState () => _MainPageState();
  }

  class _MainPageState extends State<MainPage> {

    int _currentIndex = 0;
    final _pageWidgets = [
      PageWidget(color:Colors.white, title:'Home'),
      PageWidget(color:Colors.blue, title:'Album'),
      PageWidget(color:Colors.orange, title:'Chat'),
    ];

    @override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: AppBar(
          title: Text('BottomNavigationBar'),
        ),
        body: _pageWidgets.elementAt(_currentIndex),
        bottomNavigationBar: BottomNavigationBar(
          items: <BottomNavigationBarItem>[
            BottomNavigationBarItem(icon: Icon(Icons.home), title: Text('Home')),
            BottomNavigationBarItem(icon: Icon(Icons.photo_album), title: Text('Album')),
            BottomNavigationBarItem(icon: Icon(Icons.chat), title: Text('Chat')),
          ],
          currentIndex: _currentIndex,
          fixedColor: Colors.blueAccent,
          onTap: _onItemTapped,
          type: BottomNavigationBarType.fixed,
        ),
      );
    }

    void _onItemTapped(int index) => setState(() => _currentIndex = index );
  }

  class PageWidget extends StatelessWidget {
    final Color color;
    final String title;

    PageWidget({Key key, this.color, this.title}) : super(key: key);

    @override
    Widget build(BuildContext context) {
      return Container(
        color: color,
        child: Center(
          child: Text(
            title,
            style: TextStyle(
              fontSize: 25,
            ),
          ),
        ),
      );
    }
  }