如何在 Flutter 中从 FirebaseFirestore 在 GoogleMap 上添加自定义标记？

如何解决如何在 Flutter 中从 FirebaseFirestore 在 GoogleMap 上添加自定义标记？

我正在尝试从 Firestore 数据库中显示多个标记（仅那些距离小于 2000 的标记）。但不幸的是，我没有得到想要的输出。

    @override
  void initState() {
    super.initState();

    _getCurrentLocation();

  }



 _getCurrentLocation() async {

    setCustomMarker();
    await Geolocator.getCurrentPosition(desiredAccuracy: LocationAccuracy.high)
        .then((Position position) async {

      setState(() {
        _currentPosition = position;
        print('CURRENT POS: $_currentPosition');
        mapController.animateCamera(
          CameraUpdate.newCameraPosition(
            CameraPosition(
              target: LatLng(position.latitude,position.longitude),zoom: 18.0,),);
      });
      await _getAddress();
    }).catchError((e) {
      print(e);
    });
  }

  void setCustomMarker() async{
    customIcon=await BitmapDescriptor.fromAssetImage(ImageConfiguration(devicePixelRatio: 2.5),'Assets/pointer.jpg');

    getVolunteersLocations();
  }
  getVolunteersLocations()async{


    print('get volunteer location called ');
    FirebaseFirestore.instance.collection('Volunteers').get().then((doces) {
      if (doces.docs.isNotEmpty) {

        for (int i = 0; i < doces.docs.length; ++i) {

          var distance=Geolocator.distanceBetween(_currentPosition.latitude,_currentPosition.longitude,doces.docs[i].get('lat'),doces.docs[i].get('lng') );

          print('distance $distance');
          if(distance <2000){
            print('get name ${doces.docs[i].get('v_name')}');

            maarkr.add(Marker(
              markerId: MarkerId(doces.docs[i].get('v_name')),position: LatLng(doces.docs[i].get('lat'),doces.docs[i].get('lng')),infoWindow: InfoWindow(
                title: 'Start ${doces.docs[i].get('v_name')}',snippet: _startAddress,icon:customIcon,));



          }

        }
      }
    });
  }

这是谷歌地图，脚手架中的小部件（构建方法）。我不明白我在做什么，任何帮助将不胜感激。

GoogleMap(
              markers: maarkr.toSet(),initialCameraPosition: _initialLocation,myLocationEnabled: true,myLocationButtonEnabled: false,mapType: MapType.normal,zoomGesturesEnabled: true,zoomControlsEnabled: false,polylines: Set<Polyline>.of(polylines.values),onMapCreated: (GoogleMapController controller) {
                mapController = controller;
              },