How to Draw Polygon on Google Maps in Flutter?

import 'package:flutter/material.dart';
import 'package:google_maps/Convert_Lat_Long.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);
  
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      // on below line we are specifying title of our app
      title: 'GFG',
      // on below line we are hiding debug banner
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        // on below line we are specifying theme
        primarySwatch: Colors.green,
      ),
      // First screen of our app
      home: const HomePage(),
    );
  }
}

import 'dart:async';
import 'dart:collection';
import 'package:flutter/material.dart';
import 'package:geolocator/geolocator.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';

class HomePage extends StatefulWidget {
  const HomePage({Key? key}) : super(key: key);
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  // created controller to display Google Maps
  Completer<GoogleMapController> _controller = Completer();

  // on below line we have set the camera position
  static final CameraPosition _kGoogle = const CameraPosition(
      target: LatLng(19.0759837, 72.8776559),
    zoom: 14,
  );

  Set<Polygon> _polygon = HashSet<Polygon>();
  
  // created list of locations to display polygon
  List<LatLng> points = [
    LatLng(19.0759837, 72.8776559),
    LatLng(28.679079, 77.069710),
    LatLng(26.850000, 80.949997),
    LatLng(19.0759837, 72.8776559),
  ];
  
   @override
  void initState() {
    // TODO: implement initState
    super.initState();
    //initialize polygon
    _polygon.add(
      Polygon(
        // given polygonId
        polygonId: PolygonId('1'),
        // initialize the list of points to display polygon
        points: points,
        // given color to polygon
        fillColor: Colors.green.withOpacity(0.3),
        // given border color to polygon
        strokeColor: Colors.green,
        geodesic: true,
        // given width of border
        strokeWidth: 4,
      )
    );
  }
  
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Color(0xFF0F9D58),
        // title of app
        title: Text("GFG"),
      ),
      body: Container(
        child: SafeArea(
          child: GoogleMap(
            //given camera position
            initialCameraPosition: _kGoogle,
            // on below line we have given map type
            mapType: MapType.normal,
            // on below line we have enabled location
            myLocationEnabled: true,
            myLocationButtonEnabled: true,
            // on below line we have enabled compass location
            compassEnabled: true,
            // on below line we have added polygon
            polygons: _polygon,
            // displayed google map
            onMapCreated: (GoogleMapController controller){
                _controller.complete(controller);
            },
          ),
        ),
      ),
   );
  }
}