How to show tooltip at the tapped position until the next tap is received in Maps?

class _CustomMapZoomPanBehavior extends MapZoomPanBehavior {
  late MapTapCallback onTap;
 
  @override
  void handleEvent(PointerEvent event) {
    if (event is PointerUpEvent) {
      onTap(event.localPosition);
    } 
    super.handleEvent(event);
  }
}
 
typedef MapTapCallback = void Function(Offset position);

late MapLatLng _markerPosition;
late _CustomMapZoomPanBehavior _zoomPanBehavior;
late MapShapeLayerController _controller;
late List<Model> _data;
late MapShapeSource _mapSource;
int _tappedIndex = 0;
 
@override
void initState() {
  _controller = MapShapeLayerController();
  _zoomPanBehavior = _CustomMapZoomPanBehavior()
    ..onTap = updateMarkerChange;
  _data = <Model>[
    Model('Asia', '44,579,000 sq. km.'),
    Model('Africa', '30,370,000 sq. km.'),
    Model('Europe', '10,180,000 sq. km.'),
    Model('North America', '24,709,000 sq. km.'),
    Model('South America', '17,840,000 sq. km.'),
    Model('Australia', '8,600,000 sq. km.'),
  ];
  
  _mapSource = MapShapeSource.asset(
    "assets/world_map.json",
    shapeDataField: "continent",
    dataCount: _data.length,
    primaryValueMapper: (int index) => _data[index].continent,
  );
  super.initState();
}
 
void updateMarkerChange(Offset position) {
  _markerPosition = _controller.pixelToLatLng(position);
}
 
@override
Widget build(BuildContext context) {
  return Scaffold(
    body: SfMaps(
      layers: [
        MapShapeLayer(
          source: _mapSource,
          zoomPanBehavior: _zoomPanBehavior,
          controller: _controller,
          shapeTooltipBuilder: (BuildContext context, int index) {
            _tappedIndex = index;
            if (_controller.markersCount > 0) {
              _controller.clearMarkers();
            }
            _controller.insertMarker(0);
            return SizedBox();
          },
          markerBuilder: (BuildContext context, int index) {
            return MapMarker(
              latitude: _markerPosition.latitude,
              longitude: _markerPosition.longitude,
              child: Container(
                width: 130,
                height: 45,
                color: Colors.blue,
                padding: const EdgeInsets.all(5),
                child: Text(
                    _data[_tappedIndex].continent + '\n' +
                      _data[_tappedIndex].area,
                      style: TextStyle(
                        color: Colors.white,
                        fontSize: Theme
                            .of(context)
                            .textTheme
                            .bodyText2!
                            .fontSize),
                ),
              ),
            );
          },
        ),
      ],
    ),
  );
}
 
class Model {
  const Model(this.continent, this.area);
  final String continent;
  final String area;
}