在flutter地图(openstreet)中搜索地址，但无法将相机移动到标记位置

import 'package:flutter/material.dart';
import 'package:flutter_map/flutter_map.dart';
import 'package:geocoder/geocoder.dart';
import 'package:flutter_map/plugin_api.dart';

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

class _MapPageState extends State<MapPage> {
  final MapController _mapController = MapController();
  TextEditingController _searchController = TextEditingController();
  List<Marker> _markers = [];

  void searchAddress(String address) async {
    List<Address> addresses = await Geocoder.local.findAddressesFromQuery(address);
    if (addresses.isNotEmpty) {
      Address firstAddress = addresses.first;
      double latitude = firstAddress.coordinates.latitude;
      double longitude = firstAddress.coordinates.longitude;

      setState(() {
        _markers = [
          Marker(
            width: 80.0,
            height: 80.0,
            point: LatLng(latitude, longitude),
            builder: (ctx) => Container(
              child: Icon(
                Icons.location_on,
                color: Colors.red,
              ),
            ),
          ),
        ];
      });

      _mapController.move(LatLng(latitude, longitude), 15.0);
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Map Search'),
      ),
      body: Column(
        children: [
          Padding(
            padding: EdgeInsets.all(16.0),
            child: TextField(
              controller: _searchController,
              decoration: InputDecoration(
                labelText: 'Search Address',
              ),
            ),
          ),
          Expanded(
            child: FlutterMap(
              mapController: _mapController,
              options: MapOptions(
                center: LatLng(0, 0),
                zoom: 10.0,
              ),
              layers: [
                TileLayerOptions(
                  urlTemplate: 'https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png',
                  subdomains: ['a', 'b', 'c'],
                ),
                MarkerLayerOptions(markers: _markers),
              ],
            ),
          ),
        ],
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          String address = _searchController.text;
          searchAddress(address);
        },
        child: Icon(Icons.search),
      ),
    );
  }
}