我想明白了如前所述，mapbox_maps_flutter：0.4.4目前与mapbox_gl不兼容。添加custom_marker的方法是将点注解与注解管理器结合使用。
下面是设置的样子：

MapboxMap? mapboxMap;
    PointAnnotationManager? pointAnnotationManager;
    PointAnnotation? pointAnnotation;
    
    _onMapCreated(MapboxMap mapboxMap) async {
        this.mapboxMap = mapboxMap;
        mapboxMap.annotations.createPointAnnotationManager().then((value) async {
          pointAnnotationManager = value;
          _createMarker();
        });
      }

Future<void> _createMarker({double currentLat = 0, double currentLong = 0, }) async {
    final ByteData bytes =
    await rootBundle.load('assets/images/marker.png');
    final Uint8List list = bytes.buffer.asUint8List();

    pointAnnotationManager
        ?.create(PointAnnotationOptions(
        geometry: Point(
            coordinates: Position(
              currentLong == 0
                  ? widget.postLongitude != 0 ? widget.postLongitude : widget.location.longitude
                  : currentLong,
              currentLat == 0
                  ? widget.postLatitude != 0 ? widget.postLatitude : widget.location.latitude
                  : currentLat,
            )).toJson(),
        iconSize: 2.5,
        iconOffset: [0.0, -10.0],
        symbolSortKey: 10,
        image: list))
        .then((value) => pointAnnotation = value);
  }

以上是如何创建标记并将其放置在任意初始gps位置。下面显示了当您在Map上拖动滚动或单击Map内的任何位置时如何移动标记：

Widget _map() {
    return SizedBox(
      height: MediaQuery.of(context).size.height * 0.8, //mapbox needs to have a height
      child: MapWidget(
          resourceOptions: ResourceOptions(accessToken: MAPBOX_ACCESS_TOKEN),
        onMapCreated: _onMapCreated,
        key: const ValueKey("mapWidget"),
        onScrollListener: (screenCoordinate) {
          pointAnnotationManager?.deleteAll();
          _createMarker(currentLat: screenCoordinate.x, currentLong: screenCoordinate.y);
        },
        onTapListener: (screenCoordinate) async {
          pointAnnotationManager?.deleteAll();
          _createMarker(currentLat: screenCoordinate.x, currentLong: screenCoordinate.y);
          setState(()  {});
        },
      )
    );
  }