code: public static int getSelectableBackground(Context ctx) {
          // If we're running on Honeycomb or newer, then we can use the Theme's
          // selectableItemBackground to ensure that the View has a pressed state
          TypedValue outValue = new TypedValue();
          //it is important here to not use the android.R because this wouldn't add the latest drawable
          ctx.getTheme().resolveAttribute(R.attr.selectableItemBackground, outValue, true);
          return outValue.resourceId;
      }
docs: helper to get the system default selectable background
  
  @param ctx
  @return