Flutter 从当前位置导航到固定位置不起作用

Question

这是我的第一个 Flutter/dart 项目，所以我是个大人物，这个项目仅供学校使用。 其他一切都很好......

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:flutter_polyline_points/flutter_polyline_points.dart';
import 'package:location/location.dart';

class OrderTrackingPage extends StatefulWidget {
  const OrderTrackingPage({Key? key}) : super(key: key);

  @override
  State<OrderTrackingPage> createState() => OrderTrackingPageState();
}

class OrderTrackingPageState extends State<OrderTrackingPage> {
  final Completer<GoogleMapController> _controller = Completer();

  static const LatLng sourceLocation = LatLng(48.71718424892447, 21.25749138819902);
  static const LatLng destination = LatLng(48.72045571827437, 21.25829794921262);
  BitmapDescriptor sourceIcon = BitmapDescriptor.defaultMarker;
  BitmapDescriptor destinationIcon = BitmapDescriptor.defaultMarker;
  BitmapDescriptor currentLocationIcon = BitmapDescriptor.defaultMarker;
  void setCustomMarkerIcon() {
    BitmapDescriptor.fromAssetImage(
            ImageConfiguration.empty, "assets/Pin_source.png")
        .then(
      (icon) {
        sourceIcon = icon;
      },
    );
    BitmapDescriptor.fromAssetImage(
            ImageConfiguration.empty, "assets/Pin_destination.png")
        .then(
      (icon) {
        destinationIcon = icon;
      },
    );
    BitmapDescriptor.fromAssetImage(
            ImageConfiguration.empty, "assets/Badge.png")
        .then(
      (icon) {
        currentLocationIcon = icon;
      },
    );
  }

  List<LatLng> polylineCoordinates = [];
  LocationData? currentLocation;
  

  void getCurrentLocation() async {
    Location location = Location();
    location.getLocation().then(
      (location) {
        currentLocation = location;
        
        setState(() {});
      },
    );
    GoogleMapController googleMapController = await _controller.future;
    location.onLocationChanged.listen(
      (newLoc) {
        currentLocation = newLoc;
        googleMapController.animateCamera(
          CameraUpdate.newCameraPosition(
            CameraPosition(
              zoom: 13.5,
              target: LatLng(
                newLoc.latitude!,
                newLoc.longitude!,
              ),
            ),
          ),
        );
        setState(() {});
      },
    );
  }

这是问题所在，如果有一个设置标记，折线就可以正常工作，但是当我添加当前位置纬度/经度时，我没有折线。 :C

 void getPolyPoints() async {
    PolylinePoints polylinePoints = PolylinePoints();
    PolylineResult result = await polylinePoints.getRouteBetweenCoordinates(
      'ApiKey', // Your Google Map Key
      PointLatLng(currentLocation!.latitude!, currentLocation!.longitude!),
      PointLatLng(destination.latitude, destination.longitude),
      travelMode: TravelMode.walking
    );
    if (result.points.isNotEmpty) {
      result.points.forEach(
        (PointLatLng point) => polylineCoordinates.add(
          LatLng(point.latitude, point.longitude),
        ),
      );
      setState(() {});
    }
  }

  @override
  void initState() {
    super.initState();
    getPolyPoints();
    getCurrentLocation();
    setCustomMarkerIcon();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: currentLocation == null
          ? const Center(child: Text("Loading"))
          : GoogleMap(
            
              initialCameraPosition: CameraPosition(
                target: LatLng(
                    currentLocation!.latitude!, currentLocation!.longitude!),
                zoom: 13.5,
              ),
              markers: {
                Marker(
                  markerId: const MarkerId("currentLocation"),
                  icon: currentLocationIcon,
                  position: LatLng(
                      currentLocation!.latitude!, currentLocation!.longitude!),
                ),
                Marker(
                  markerId: MarkerId("destination"),
                  icon: destinationIcon,
                  position: destination,
                ),
              },
              onMapCreated: (mapController) {
                _controller.complete(mapController);
              },
              polylines: {
                Polyline(
                  polylineId: const PolylineId("route"),
                  points: polylineCoordinates,
                  color: const Color(0xFF7B61FF),
                  width: 6,
                ),
              },
            ),
    );
  }
}

非常感谢您的帮助。