如何在flutter中缩放两个Google地图标记

dependencies:
  flutter:
    sdk: flutter
  google_maps_flutter: ^2.0.6  # 请使用最新版本

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

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: MapScreen(),
    );
  }
}

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

class _MapScreenState extends State<MapScreen> {
  GoogleMapController? _controller;
  final Set<Marker> _markers = {};
  final LatLng _marker1 = LatLng(37.7749, -122.4194); // 旧金山
  final LatLng _marker2 = LatLng(34.0522, -118.2437); // 洛杉矶

  @override
  void initState() {
    super.initState();
    _markers.add(Marker(
      markerId: MarkerId('marker1'),
      position: _marker1,
    ));
    _markers.add(Marker(
      markerId: MarkerId('marker2'),
      position: _marker2,
    ));
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Google Maps Zoom to Markers'),
      ),
      body: GoogleMap(
        initialCameraPosition: CameraPosition(
          target: _marker1,
          zoom: 10,
        ),
        markers: _markers,
        onMapCreated: (GoogleMapController controller) {
          _controller = controller;
          _zoomToFitMarkers();
        },
      ),
    );
  }

  void _zoomToFitMarkers() {
    if (_controller == null) return;

    LatLngBounds bounds;
    if (_marker1.latitude > _marker2.latitude && _marker1.longitude > _marker2.longitude) {
      bounds = LatLngBounds(southwest: _marker2, northeast: _marker1);
    } else if (_marker1.longitude > _marker2.longitude) {
      bounds = LatLngBounds(
          southwest: LatLng(_marker1.latitude, _marker2.longitude),
          northeast: LatLng(_marker2.latitude, _marker1.longitude));
    } else if (_marker1.latitude > _marker2.latitude) {
      bounds = LatLngBounds(
          southwest: LatLng(_marker2.latitude, _marker1.longitude),
          northeast: LatLng(_marker1.latitude, _marker2.longitude));
    } else {
      bounds = LatLngBounds(southwest: _marker1, northeast: _marker2);
    }

    _controller!.animateCamera(CameraUpdate.newLatLngBounds(bounds, 50));
  }
}