code: public static StateListDrawable getSelectablePressedBackground(Context ctx, @ColorInt int selected_color, int pressed_alpha, boolean animate) {
          StateListDrawable states = getSelectableBackground(ctx, selected_color, animate);
          ColorDrawable clrPressed = new ColorDrawable(adjustAlpha(selected_color, pressed_alpha));
          states.addState(new int[]{android.R.attr.state_pressed}, clrPressed);
          return states;
      }
docs: helper to get the system default selectable background inclusive an active and pressed state
  
  @param ctx            the context
  @param selected_color the selected color
  @param pressed_alpha  0-255
  @param animate        true if you want to fade over the states (only animates if API newer than Build.VERSION_CODES.HONEYCOMB)
  @return the StateListDrawable