Correct way to exit app ;)

code:

@Override
public void onBackPressed() {
    println("by by..");
    
    if(android.os.Build.VERSION.SDK_INT>=16 && android.os.Build.VERSION.SDK_INT<21){
        getActivity().finishAffinity();
    } else if(android.os.Build.VERSION.SDK_INT>=21){
        getActivity().finishAndRemoveTask();
    }
    
    
}

Works on Actual Android devices 2020.