“StreamSubscription '不能被分配给‘StreamSubscription>’

Question

目前正在学习扑动和得到这个错误，而试图检测到设备的位置：

类型“StreamSubscription”的值不能被分配给类型的变量“StreamSubscription>”

我下面的一个在线教程，但不知何故，得到这个错误。

import 'package:flutter/material.dart';
import 'package:flutter_map/flutter_map.dart';
import 'package:location/location.dart';
import 'dart:async';
import 'package:flutter/services.dart';

class MainPage extends StatefulWidget {

  @override
  State<StatefulWidget> createState() => AppState();
} 

class AppState extends State<MainPage> {

  Map<String,double> currentLocation = new Map();
  StreamSubscription<Map<String,double>> locationSubscription;

  var location = new Location();
  String error;

  void initState() {
    super.initState();

    currentLocation['latitude'] = 0.0;
    currentLocation['longitude'] = 0.0;

    initPlatformState();

    locationSubscription = 
    location.onLocationChanged().listen((Map<String,double> result) {
      setState(() {
        currentLocation = result; 
      });
    });
  }

  void initPlatformState() async{
    Map<String,double> myLocation;
    try {
      myLocation = await location.getLocation();
      error="";
    } on PlatformException catch(e) {
      if(e.code == 'PERMISSION_DENIED')
        error = "permission denied";
      else if(e.code == "PERMISSION_DENIED_NEVER_ASK")
        error = "permission denied";
      myLocation = null;
    }

    setState(() {
      currentLocation = myLocation; 
    });
  }

  @override
  Widget build (BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        centerTitle: true,
        title: Text(""),
        automaticallyImplyLeading: false,
      ),
      body: Container(
        child: FlutterMap(
          options: MapOptions(
          ),
          layers: [
            TileLayerOptions(

            ),
          ]
        ),
      )
    ); 
  } 
}

我会为任何建议非常感谢。下面是我跟着视频：https://www.youtube.com/watch?v=K4nYTayjofY&t=321s

Answer 1

貌似教程使用location插件的旧版本完成，因为V2.0.0他们改变了API返回结构化数据，而不是地图。

https://github.com/Lyokone/flutterlocation/blob/master/CHANGELOG.md

所以，你需要更改你的所有Map<String, double>类型LocationData或设置你的插件版本^1.4.0。

Answer 2

我尝试过很多办法，直到我发现多亏了谁帮助另一个扑Facebook的group.Make确保您pubspec.yaml更新位置到最新版本一个善良的人这样

dependencies:
  location: ^2.3.5

然后将其更改为下面的代码：

  LocationData _currentLocation;
  StreamSubscription<LocationData> _locationSubscription;

  var _locationService = new Location();
  String error;

  void initState() {
    super.initState();

    initPlatformState();

    _locationSubscription = _locationService
        .onLocationChanged()
        .listen((LocationData currentLocation) async {
      setState(() {
        _currentLocation = currentLocation;
      });
    });
  }

  void initPlatformState() async {
    try {
      _currentLocation = await _locationService.getLocation();


    } on PlatformException catch (e) {
      if (e.code == 'PERMISSION_DENIED') {
        error = 'Permission denied';
      }else if(e.code == "PERMISSION_DENIED_NEVER_ASK"){
        error = 'Permission denied';
      }
      _currentLocation = null;
    }

您可以访问的经度和纬度

_currentLocation.longitude和_currentLocation.latitude

这些将返回双精度值。另外，还有一些可在https://pub.dev/packages/location#-readme-tab-更多的选择