duplicate class android.support.v4.app.inotificationsidechannel found in modules core-1.3.1-runtime (androidx.core:core:1.3.1) and support-v4-23.1.0-runtime (com.android.support:support-v4:23.1.0) 에러가 뜰 때 해결법 gradle.properties android.useAndroidX=true android.enableJetifier=true 추가해주면 끝..!~!~~~!!!
