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