streambuilder를 통해서 갱신될 때 마다 값을 변경 import 'package:flutter/material.dart'; import 'package:firebase_core/firebase_core.dart'; import 'package:cloud_firestore/cloud_firestore.dart'; void main() async { WidgetsFlutterBinding.ensureInitialized(); await Firebase.initializeApp(); runApp(MyApp()); } class MyApp extends StatelessWidget { @override Widget build(BuildContext context) { return MaterialApp(..