##端的に言うと
値が変更されたことをclassへ伝えるやつ
setStateがないと、動的に値の変更を画面に反映できない。。！！
## 注意
stateFulWidgetでしか使えないよ！！
More than 1 year has passed since last update.
Register as a new user and use Qiita more conveniently
- You get articles that match your needs
- You can efficiently read back useful information
- You can use dark theme