code: public final void setDialogIcon(@Nullable final Bitmap dialogIcon) {
          this.dialogIcon = new BitmapDrawable(getContext().getResources(), dialogIcon);
          this.dialogIconBitmap = dialogIcon;
          this.dialogIconId = -1;
      }
docs: Sets the icon of the preference's dialog.
  
  @param dialogIcon
  The dialog, which should be set, as an instance of the class {@link Bitmap} or null,
  if no icon should be shown in the dialog