如何在Flutter中让用户在地图上手动设置位置

import 'package:flutter/material.dart';
import 'package:flutter_map/flutter_map.dart';
import 'package:latlong/latlong.dart';

class MapPage extends StatefulWidget {
  @override
  _MapPageState createState() => _MapPageState();
}

class _MapPageState extends State<MapPage> {
  MapController _mapController = MapController();
  LatLng _selectedLocation;

  void _handleTap(LatLng tappedPoint) {
    setState(() {
      _selectedLocation = tappedPoint;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Map'),
      ),
      body: FlutterMap(
        mapController: _mapController,
        options: MapOptions(
          center: LatLng(0, 0),
          zoom: 10.0,
          onTap: _handleTap, // 绑定点击事件处理函数
        ),
        layers: [
          TileLayerOptions(
            urlTemplate: 'https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png',
            subdomains: ['a', 'b', 'c'],
          ),
          MarkerLayerOptions(
            markers: [
              if (_selectedLocation != null)
                Marker(
                  width: 40.0,
                  height: 40.0,
                  point: _selectedLocation,
                  builder: (ctx) => Container(
                    child: Icon(
                      Icons.location_on,
                      color: Colors.red,
                    ),
                  ),
                ),
            ],
          ),
        ],
      ),
    );
  }
}