code: public final void setDialogHeaderBackground(@Nullable final Bitmap background) {
          this.dialogHeaderBackground = new BitmapDrawable(getContext().getResources(), background);
          this.dialogHeaderBackgroundBitmap = background;
          this.dialogHeaderBackgroundId = -1;
          this.dialogHeaderBackgroundColor = -1;
      }
docs: Sets the background of the header of the preference's dialog.
  
  @param background
  The background, which should be set, as an instance of the class {@link Bitmap} or
  null, if no custom background should be set