code: private void obtainBackground(@StyleRes final int themeResourceId) {
          TypedArray typedArray = getContext().getTheme().obtainStyledAttributes(themeResourceId,
                  new int[]{R.attr.materialDialogBackground});
          int resourceId = typedArray.getResourceId(0, 0);
  
          if (resourceId != 0) {
              setBackground(resourceId);
          } else {
              setBackgroundColor(
                      ContextCompat.getColor(getContext(), R.color.dialog_background_light));
          }
      }
docs: Obtains the background from a specific theme.
  
  @param themeResourceId
  The resource id of the theme, the background should be obtained from, as an {@link
  Integer} value