[트러블 슈팅] 16. Flutter 변수 선언을 build() 안에서 함

import 'package:flutter/material.dart';
import 'package:flutter_shoppingcart/component/m_select_button.dart';

class MSelectHeader extends StatefulWidget {
  @override
  State<MSelectHeader> createState() => _MSelectHeaderState();
}

class _MSelectHeaderState extends State<MSelectHeader> {
  @override
  Widget build(BuildContext context) {
    // 1. 상태
    List<String> images = [
      'assets/p1.jpeg',
      'assets/p2.jpeg',
      'assets/p3.jpeg',
      'assets/p4.jpeg',
    ];

    int selectedIndex = 0;

    // 2. 행위
    void onClick(int index) {
      selectedIndex = index;
      print("선택한 번호: ${selectedIndex}");
      print("선택한 번호: ${images[selectedIndex]}.");
      setState(() {});
    }

    return Padding(
      padding: EdgeInsets.symmetric(horizontal: 16),
      child: Column(
        children: [
          ClipRRect(
            borderRadius: BorderRadius.circular(5),
            child: AspectRatio(
              aspectRatio: 5 / 3,
              child: Image.asset("${images[selectedIndex]}", fit: BoxFit.cover),
            ),
          ),
          Padding(
            padding: EdgeInsets.symmetric(vertical: 20),
            child: Row(
              mainAxisAlignment: MainAxisAlignment.spaceAround,
              children: [
                MSelectorButton(() => onClick(0)),
                MSelectorButton(() => onClick(1)),
                MSelectorButton(() => onClick(2)),
                MSelectorButton(() => onClick(3)),
              ],
            ),
          ),
        ],
      ),
    );
  }
}