如何使用GoogleMap flutter *而不是MapView*使用GoogleMap flutter在两个标记之间绘制路径

GoogleMap(
  onMapCreated: (GoogleMapController controller) {
    _controller.complete(controller);
  },
  initialCameraPosition: CameraPosition(
    target: LatLng(37.7749, -122.4194), // 设置初始地图位置
    zoom: 12.0, // 设置初始缩放级别
  ),
),

Marker(
  markerId: MarkerId("起点"),
  position: LatLng(37.7749, -122.4194),
  icon: BitmapDescriptor.defaultMarker,
  infoWindow: InfoWindow(
    title: "起点",
    snippet: "San Francisco",
  ),
),
Marker(
  markerId: MarkerId("终点"),
  position: LatLng(37.3352, -122.0498),
  icon: BitmapDescriptor.defaultMarker,
  infoWindow: InfoWindow(
    title: "终点",
    snippet: "Cupertino",
  ),
),

Polyline(
  polylineId: PolylineId("路径"),
  points: [
    LatLng(37.7749, -122.4194),
    LatLng(37.3352, -122.0498),
  ],
  color: Colors.blue,
  width: 5,
),

import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';

class MapScreen extends StatefulWidget {
  @override
  _MapScreenState createState() => _MapScreenState();
}

class _MapScreenState extends State<MapScreen> {
  Completer<GoogleMapController> _controller = Completer();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("地图示例"),
      ),
      body: GoogleMap(
        onMapCreated: (GoogleMapController controller) {
          _controller.complete(controller);
        },
        initialCameraPosition: CameraPosition(
          target: LatLng(37.7749, -122.4194),
          zoom: 12.0,
        ),
        markers: {
          Marker(
            markerId: MarkerId("起点"),
            position: LatLng(37.7749, -122.4194),
            icon: BitmapDescriptor.defaultMarker,
            infoWindow: InfoWindow(
              title: "起点",
              snippet: "San Francisco",
            ),
          ),
          Marker(
            markerId: MarkerId("终点"),
            position: LatLng(37.3352, -122.0498),
            icon: BitmapDescriptor.defaultMarker,
            infoWindow: InfoWindow(
              title: "终点",
              snippet: "Cupertino",
            ),
          ),
        },
        polylines: {
          Polyline(
            polylineId: PolylineId("路径"),
            points: [
              LatLng(37.7749, -122.4194),
              LatLng(37.3352, -122.0498),
            ],
            color: Colors.blue,
            width: 5,
          ),
        },
      ),
    );
  }
}