sprockets/src/main/java/net/sf/sprockets/widget/SearchViews.java
public static SearchView setBackground(SearchView view, @DrawableRes int drawableId) {
        int id = view.getResources().getIdentifier("android:id/search_plate", null, null);
        if (id > 0) {
            View search = view.findViewById(id);
            if (search != null) {
                search.setBackgroundResource(drawableId);
            }
        }
        return view;
    }
public static SearchView setBackground(SearchView view, @DrawableRes int drawableId) {
        int id = view.getResources().getIdentifier("android:id/search_plate", null, null);
        if (id > 0) {
            View search = view.findViewById(id);
            if (search != null) {
                search.setBackgroundResource(drawableId);
            }
        }
        return view;
    }
Override the default background with a theme version.