TextView text 보여줌EditText 기입과 편집을 할 수 있슴Button and other clickable elements (such as RadioButton, CheckBox, and Spinner) to provide interactive behavi
참고 https://roqkfwk.tistory.com/40#recentComments 에러-빌드시 Nullable에 빨간줄 https://likejirak.tistory.com/255