android studio cardview background transparent

1                 <androidx.cardview.widget.CardView
2                                    xmlns:card_view="http://schemas.android.com/apk/res-auto"
3                                    xmlns:android="http://schemas.android.com/apk/res/android"
4                                    android:id="@+id/cardView"
5                                    android:layout_width="wrap_content"
6                                    android:layout_height="wrap_content"
7                                    android:layout_marginTop="64dp"
8                                    card_view:cardBackgroundColor="@android:color/transparent"
9                                    app:cardCornerRadius="20dp"
10                                    app:cardElevation="0dp">