createState() => _TopState(); } class _TopState extends State { // 1. 상태 int num = 1; // 2. 행위 void increase(){ num++; setSta"> createState() => _TopState(); } class _TopState extends State { // 1. 상태 int num = 1; // 2. 행위 void increase(){ num++; setSta"> createState() => _TopState(); } class _TopState extends State { // 1. 상태 int num = 1; // 2. 행위 void increase(){ num++; setSta">

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import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: HomePage(),
    );
  }
}

class HomePage extends StatelessWidget {
  const HomePage({super.key});

  @override
  Widget build(BuildContext context) {
    print("HomePage build");
    return Scaffold(
      body: SafeArea(
        child: Column(
          children: [
            Expanded(child: Top()),
            Expanded(child: Bottom()),
          ],
        ),
      ),
    );
  }
}

class Top extends StatefulWidget {
  const Top({super.key});

  @override
  State<Top> createState() => _TopState();
}

class _TopState extends State<Top> {

  // 1. 상태
  int num = 1;

  // 2. 행위
  void increase(){
    num++;
    setState(() {});
  }

  @override
  Widget build(BuildContext context) {
    print("Top build");
    return Column(
      children: [
        Top1(num),
        Top2(increase),
      ],
    );
  }
}

class Top1 extends StatelessWidget {
  final num;

  Top1(this.num);

  @override
  Widget build(BuildContext context) {
    print("Top 1 build");
    return Expanded(
      child: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text("Top 1", style: TextStyle(fontSize: 40, fontWeight: FontWeight.bold)),
            Text("num : $num", style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold))
          ],
        ),
      ),
    );
  }
}

class Top2 extends StatelessWidget {
  final increase;

  Top2(this.increase);

  @override
  Widget build(BuildContext context) {
    print("Top 2 build");
    return Expanded(
      child: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text("Top 2", style: TextStyle(fontSize: 40, fontWeight: FontWeight.bold)),
            ElevatedButton(onPressed: (){
              increase();
            }, child: Icon(Icons.add))
          ],
        ),
      ),
    );
  }
}

class Bottom extends StatelessWidget {
  const Bottom({
    super.key,
  });

  @override
  Widget build(BuildContext context) {
    print("Bottom build");
    return Center(
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          Text("Bottom", style: TextStyle(fontSize: 40, fontWeight: FontWeight.bold)),
        ],
      ),
    );
  }
}