Flutter：谷歌地图自定义标记不会改变背景

Question

我在我的应用程序中使用google_maps_flutter: ^2.0.6包。 在这里，我使用提供程序将标记加载到我的应用程序中。 此外，我需要在点击时更改标记的装饰图像。 问题是我的 ontap 事件正在执行，但图像没有改变。

以下是谷歌地图小部件的代码

  Set<Marker> customMarkers = Set<Marker>();

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

  void getMarkers() {
    Future.delayed(const Duration(seconds: 2), () {
      setState(() {
        customMarkers =
            Provider.of<MapProvider>(context, listen: false).getMarkers();
      });
    });
  }

  void _onMapCreated(GoogleMapController controller) {
    mapController = controller;
  }

  @override
  Widget build(BuildContext context) {
    var con = config.SizeConfig();
    return Scaffold(
      body: Container(
        height: con.h(),
        width: con.w(),
        child: Stack(
          children: [
            GoogleMap(
              zoomControlsEnabled: false,
              mapType: MapType.normal,
              onMapCreated: (controller) {
                _onMapCreated(controller);                
              },
              markers: customMarkers,
              initialCameraPosition: CameraPosition(
                target: _center,
                zoom: 14.0,
              ),
            ),
            BackBtn(con: con),
            TitleWidget(con: con),
            BottomBtn(con: con),
          ],
        ),
      ),
    );
  }

下面是我创建的提供程序

  class MapProvider extends ChangeNotifier {
  Set<Marker> customMarkers = Set<Marker>();


  void generateMarkers(context) {
    var con = config.SizeConfig();

    var locations = [
      LatLng(56.9570879, 24.1014793),
      LatLng(56.9568659, 24.0961793),
      LatLng(56.9546749, 24.0836303),
      LatLng(56.9408639, 24.1005883),
      LatLng(56.9420809, 24.0958893)
    ];

    var markerListLength = 5;

    Future.delayed(const Duration(seconds: 2), () {
      var decorationImageDarkBlue = DecorationImage(
          image: AssetImage('${Constants.IMAGE_PATH}icon-map-pin.png'),
          fit: BoxFit.scaleDown);

      var decorationImageGreen = DecorationImage(
          image: AssetImage('${Constants.IMAGE_PATH}icon-map-pin-green.png'),
          fit: BoxFit.scaleDown);

      var decorationImageLightBlue = DecorationImage(
          image:
              AssetImage('${Constants.IMAGE_PATH}icon-map-pin-light-blue.png'),
          fit: BoxFit.scaleDown);

      var decorationImageBlack = DecorationImage(
          image: AssetImage('${Constants.IMAGE_PATH}icon-map-pin-black.png'),
          fit: BoxFit.scaleDown);

      for (var i = 0; i < markerListLength; i++) {
        var selected = i == 0
            ? decorationImageDarkBlue
            : i == 1
                ? decorationImageGreen
                : decorationImageLightBlue;

        MarkerGenerator(
          [
            Container(
              alignment: Alignment.topCenter,
              padding: EdgeInsets.all(con.initWidth(v1: 6)),
              decoration: BoxDecoration(image: selected),
              height: con.initHeight(v1: 40),
              width: con.initWidth(v1: 30.47),
              child: Container(
                  width: con.initWidth(v1: 18),
                  height: con.initWidth(v1: 18),
                  alignment: Alignment.center,
                  decoration:
                      BoxDecoration(color: kwhite, shape: BoxShape.circle),
                  child: CustomText(
                      fontColor: Color(0xFF1879D3),
                      fontSize: 12,
                      text: '$i')),
            )
          ],
          (bitmaps) {
            customMarkers.add(Marker(
                infoWindow: InfoWindow(title: "$i"),
                markerId: new MarkerId("randomText$i"),
                position: locations[i],
                icon: BitmapDescriptor.fromBytes(bitmaps.first),
                anchor: Offset(0.5, 0.5),
                onTap: () {
                  print("marker on tap executed"); // this line prints
                  selected = decorationImageBlack; //this line isn't
                  notifyListeners();
                }));
          },
        ).generate(context);
      }
    });
  }

  Set<Marker> getMarkers() {
    return customMarkers;
  }
}

这里有什么错误，我该如何解决。