anchor.diff:      _bottomSheet?.setState(() { });
     }
   
  -  void showConfigurationSheet(BuildContext appContext) {
  -    _bottomSheet = scaffoldKey.currentState.showBottomSheet((BuildContext bottomSheetContext) {
  +  void _showConfigurationSheet() {
  +    final PersistentBottomSheetController<Null> bottomSheet = scaffoldKey.currentState.showBottomSheet((BuildContext bottomSheetContext) {
         return new Container(
           decoration: new BoxDecoration(
             border: new Border(top: new BorderSide(color: Colors.black26)),
  
positive.code:           ],
          ),
        );
      });
    }
  
  
negative.code:           new IconButton(
              icon: new Icon(Icons.more_vert),
              tooltip: 'Show menu',
              onPressed: _bottomSheet == null ? _showConfigurationSheet : null,
            ),
          ],
        ),
  