@Override
      public void selectionChanged(final @NotNull ContentManagerEvent event) {
        initUI();
        if (ContentManagerEvent.ContentOperation.add == event.getOperation()) {
          showContent(event.getContent());
        }
        else if (ContentManagerEvent.ContentOperation.remove == event.getOperation()) {
          hideContent();
        }
      }
@Override
      public void selectionChanged(final @NotNull ContentManagerEvent event)