使用streambuilder更改flutter中的google地图状态

import 'dart:async';
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> {
  StreamController<LatLng> _streamController = StreamController<LatLng>();

  @override
  void dispose() {
    _streamController.close();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Google Map'),
      ),
      body: StreamBuilder<LatLng>(
        stream: _streamController.stream,
        builder: (context, snapshot) {
          if (snapshot.hasData) {
            LatLng position = snapshot.data;
            return GoogleMap(
              initialCameraPosition: CameraPosition(
                target: position,
                zoom: 15.0,
              ),
              markers: Set<Marker>.from([
                Marker(
                  markerId: MarkerId('currentLocation'),
                  position: position,
                ),
              ]),
            );
          } else {
            return Center(
              child: CircularProgressIndicator(),
            );
          }
        },
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () {
          // Simulate getting new location data
          LatLng newPosition = LatLng(37.4219999, -122.0840575);
          _streamController.add(newPosition);
        },
        child: Icon(Icons.location_on),
      ),
    );
  }
}