https://www.flutter-study.dev/firebase-app/about-firebase-app
Firebaseを使ったアプリ概要
https://qiita.com/tanuki4/items/419fd9c802a1102e7e08
が2018年12月24日に作成
flutterでfirebaseを使いチャットアプリを作る(firestore編)
https://medium.com/flutter-community/a-chat-application-flutter-firebase-1d2e87ace78f
A Chat Application — Flutter & Firebase
Yoganathan Shiv
Dec 30, 2020
→ Input Widgetがお勧め