以编程方式选择google地图flutter上的标记

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> {
  GoogleMapController _mapController;
  Set<Marker> _markers = {};

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Google Maps Flutter'),
      ),
      body: GoogleMap(
        initialCameraPosition: CameraPosition(
          target: LatLng(37.7749, -122.4194), // 设置初始位置
          zoom: 12.0, // 设置初始缩放级别
        ),
        markers: _markers, // 添加标记
        onMapCreated: (GoogleMapController controller) {
          _mapController = controller;
        },
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          // 在按钮点击时添加一个标记
          setState(() {
            _markers.add(
              Marker(
                markerId: MarkerId('marker1'),
                position: LatLng(37.7749, -122.4194),
                infoWindow: InfoWindow(
                  title: 'San Francisco',
                  snippet: 'A beautiful city',
                ),
              ),
            );
          });
        },
        child: Icon(Icons.add),
      ),
    );
  }
}