I was able to solve it by setting the background of the default searchview plate as follows
int searchPlateId = searchView.getContext().getResources()
.getIdentifier("android:id/search_plate", null, null);
View searchPlateView = searchView.findViewById(searchPlateId);
if (searchPlateView != null) {
searchPlateView.setBackgroundColor(Color.BLACK);
}
This article helped.article link