谷歌地图不显示

如果手动设置坐标

target: LatLng(48.5244722, 39.2643343),

，显示地图。如果坐标是动态确定的，则不会使用package:geolocator显示地图。为什么？下面是完整的代码示例和屏幕截图。

主要.dart

import 'package:flutter/material.dart';

import 'package:google_maps_flutter/google_maps_flutter.dart';

import 'package:geolocator/geolocator.dart';

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

class MyApp extends StatelessWidget {
 @override
 Widget build(BuildContext context) {
  return MaterialApp(
   debugShowCheckedModeBanner: false,
   title: 'Name App',
   theme: ThemeData(
    primarySwatch: Colors.blue,
   ),
   home: Scaffold(
    appBar: AppBar(
     title: Text('Name Page'),
    ),
    body: MyHomePage(),
   ),
  );
 }
}

class MyHomePage extends StatefulWidget {
 @override
 _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {

 String _str = ''; //для проверки
 double _latitude = 0.0;  //широта
 double _longitude = 0.0; //долгота

 @override
 void initState() {
  super.initState();
  _getPosition().then((value) {
   _latitude = value.latitude;
   _longitude = value.longitude;
   _str = '$_latitude\n$_longitude';
  });
 }

 @override
 void dispose() {
  super.dispose();

 }

 void _f1() {
  setState(() {

  });
 }

 Future<Position> _getPosition() async {
  Position position = await Geolocator.getCurrentPosition(desiredAccuracy: LocationAccuracy.best);
  return position;
 }

 @override
 Widget build(BuildContext context) {
  return Stack(
   children: [
    GoogleMap(
     initialCameraPosition: CameraPosition(
      //target: LatLng(48.5244722, 39.2643343),
      target: LatLng(_latitude, _longitude),
      zoom: 19.151926040649414,
      bearing: 222.8334901395799,
     ),
     mapType: MapType.hybrid,
    ),
    Align(
     alignment: Alignment(0.0, 0.95),
     child: Text(
      _str,
      style: TextStyle(
       fontSize: 20.0,
      ),
     ),
    ),
   ],
  );
 }

}