플러터 docs 읽기 https://docs.flutter.dev/development/ui/interactive#stateful-and-stateless-widgets Adding interactivity to your Flutter app How to implement a stateful widget that responds to taps. docs.flutter.dev Stateful and stateless widgets A widget is either stateful or stateless. If a widget can change—when a user interacts with it, for example—it’s stateful. A stateless widget never changes...