我在主构建函数中调用了Google maps的一个示例，如下所示：

return GoogleMap(
  onMapCreated: _onMapCreated,
  options: GoogleMapOptions(
    cameraPosition: CameraPosition(
      target: _center1,
      zoom: 11.0,
    ),
  ),
);

在“_onMapCreated”函数中，我有迭代器：

widget.model.allItems.forEach((item) {
  //print("XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX");
  print(item.lat);

  var newItem = LatLng(double.parse(item.lat), double.parse(item.lon));
  mapController.addMarker(
    MarkerOptions(
      icon: BitmapDescriptor.fromAsset(assetName),
      position: newItem,
    ),
  );
});

这对我有用

在第一个例子中，GoogleMapController参数和你的局部变量有相同的名字，所以基本上，局部变量被遮蔽了，你给它自己赋函数参数值。重命名这两个变量中的一个应该可以解决这个问题。

void populateOrder(Item item) async {
if (item != null) {
  for (int i = 0; i < item.feature.length; i++) {
    var position = item.feature[i];
    if (position != null) {
      try {
        if (double.parse(position.latitude) != null &&
            double.parse(position.longitude) != null) {
           mapController.clearMarkers().then((value){
             mapController.addMarker(
              MarkerOptions(
                position: LatLng(double.parse(position.latitude),
                    double.parse(position.longitude)),
                infoWindowText: InfoWindowText(position.schet, ""),
                icon: BitmapDescriptor.defaultMarker,
              ),
            );
          });
        }
      } catch (e) {
        print(e);
      }
    }
  }
}

}

void _onMapCreated(GoogleMapController controller) {
mapController = controller;
populateOrder(itemize);
Future.delayed(Duration(seconds: 6));

}

库已更新：这就是我在Map上显示多个标记的方法。

Completer<GoogleMapController> _controller = Completer();
         // initial camera position
         CameraPosition _cameraPos;
     // A map of markers
         Map<MarkerId, Marker> markers = <MarkerId, Marker>{};
        // function to generate random ids
        int generateIds() {
              var rng = new Random();
              var randomInt;      
                randomInt = rng.nextInt(100);
                print(rng.nextInt(100));
              return randomInt;
            }

            //call this function in initstate
            // I'm getting a json Object with locations from an 
            // external api
            buildMarkers() {
                  for (var i = 0; i < gridItem.locations.length; i++) {
                    var markerIdVal = generateIds();
                  final MarkerId markerId = MarkerId(markerIdVal.toString());
                    final Marker marker = Marker(
                  markerId: markerId,
                  position: LatLng(
                   gridItem.locations[i].latitude,
                    gridItem.locations[i].longitude,
                  ),
                  infoWindow: InfoWindow(title: gridItem.locations[i].place, snippet: gridItem.locations[i].region),
                );
// you could do setState here when adding the markers to the Map
                 markers[markerId] = marker;

                  }
                  print("Length:: + ${markers.length}");
                }
    // your Googlemaps Widget somewhere in your widget tree
    GoogleMap(
              mapType: MapType.normal,
              initialCameraPosition: _cameraPos,
              gestureRecognizers: <Factory<OneSequenceGestureRecognizer>>[Factory<OneSequenceGestureRecognizer>(()=>ScaleGestureRecognizer())].toSet(),
              markers: Set<Marker>.of(markers.values),
              onMapCreated: (GoogleMapController controller) {
                             _controller.complete(controller);}),