rippleEnabled is false

recycler_headercell.xml

<com.ebay.customrippleview.RippleTextView
    android:id="@+id/course_index"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:focusable="true"
    android:gravity="center"
    android:paddingBottom="4dp"
    android:paddingTop="4dp"
    android:text="@string/course_index"
    android:textColor="@android:color/white"
    android:textSize="12sp"
    android:textStyle="bold"
    app:rippleEnabled="false"
    app:backgroundColor="@color/background" />