main.dart

import 'package:flutter/material.dart';

void main() {
  runApp(const App());
}

class App extends StatelessWidget {
  const App({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: StatefulPage(),
    );
  }
}

class StatefulPage extends StatefulWidget {
  const StatefulPage({Key? key}) : super(key: key);

  @override
  StatefulPageState createState() => StatefulPageState();
}

class StatefulPageState extends State<StatefulPage> {
  bool isRow = false;
  static const List<Widget> childrenConst = [
    StatefulConst(),
    StatelessConst(),
  ];

  @override
  Widget build(BuildContext context) {
    print('Build: StatefulPageState');
    return Scaffold(
      appBar: AppBar(title: const Text('Sample const')),
      body: Center(
        child: isRow
            ? Column(children: childrenConst)
            : Row(children: childrenConst),
      ),
      floatingActionButton: FloatingActionButton(
        child: const Icon(Icons.add),
        onPressed: () => setState(() {
          isRow = !isRow;
        }),
      ),
    );
  }
}

class StatefulConst extends StatefulWidget {
  const StatefulConst({Key? key}) : super(key: key);

  @override
  StatefulConstState createState() => StatefulConstState();
}

class StatefulConstState extends State<StatefulConst> {
  @override
  Widget build(BuildContext context) {
    print('Build: StatefulConstState');
    return Container(
      width: 10,
      height: 10,
      color: Colors.amber,
    );
  }
}

class StatelessConst extends StatelessWidget {
  const StatelessConst({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    print('Build: StatelessConst');
    return Container(
      width: 10,
      height: 10,
      color: Colors.purple,
    );
  }
}