code: void onColumnSelect(final int index, final boolean selected) {
          final DataColumnDef columnDef = acceptableColumns.get(index);
          if (selected) {
              listEditor.getList().add(columnDef.clone());
          } else {
              listEditor.getList().remove(columnDef);
          }
          columnsChangedEvent.fire(new ColumnsChangedEvent(this, listEditor.getList()));
      }
docs: ***********************************************************
  * VIEW CALLBACK METHODS **
  ***********************************************************