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sdk 29 사용

import androidx.appcompat.app.AppCompatActivity;
gradle.properties
android.useAndroidX=true
android.enableJetifier=true

dependencies {

implementation 'androidx.appcompat:appcompat:1.0.0'

 Refector을 클릭한 후 , 아래쪽에 있는 Migrate to Androidx를 클릭합니다