引发了另一个异常:NoSuchMethodError:在null上调用了getter'latitude' [英] Another exception was thrown: NoSuchMethodError: The getter 'latitude' was called on null

问题描述

我正在尝试使用Flutter中的Location软件包，但是当我尝试在我的应用中显示纬度和经度时，我收到一条错误消息，指出"getter'纬度'被调用为null."我的设备上的位置服务是否可能有问题?当我单击屏幕上的消息时，还会提示我一个弹出窗口，提示为了获得更好的体验，请打开使用Google位置服务的设备位置"，但是我已经在应用程序中启用了位置服务的权限.以下是我的代码

I am trying to utilize the Location package in Flutter, but when I try to display the Latitude and Longitude in my app I am getting an error stating "The getter 'latitude' was called on null." Is it possible that there's something wrong with the location services on my device? I am also prompted with a popup when I click on the screen stating "For a better experience, turn on device location, which uses Google's location service" but I already enabled permissions for location services in the app. Below is my code

import 'package:flutter/material.dart'; 
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:provider/provider.dart';
import 'package:wasteagram/data/firestore_service.dart';
import 'package:location/location.dart'; 
import 'dart:async';
import 'package:wasteagram/model/user_location.dart'; 



class DetailPage extends StatefulWidget {

  final DocumentSnapshot post; 

  DetailPage({this.post}); 

  @override
  _DetailPageState createState() => _DetailPageState();
}

class _DetailPageState extends State<DetailPage> {

  LocationData locationData; 

  @override
  void initState() {
    super.initState(); 
    retrieveLocation(); 
  }

  void retrieveLocation() async {
    var locationService = Location(); 
    locationData = await locationService.getLocation(); 
    setState(() {

    });

  }

  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.post.data["wastedate"])
      ), 
      body: Center(
        child: Container( 
          child: Column(
            children: <Widget> [
              Image.network(widget.post.data["image"]),
              Text(widget.post.data["wastedate"]), 
              Text(widget.post.data["wastenumber"]), 
              Text('Latitude: ${locationData.latitude}'),
              Text('Longitude: ${locationData.longitude}')

            ]
          )
        )
      ),
    );
  }
}

推荐答案

尝试将将来的构建器用于异步方法回调，例如

try to use future builder for async method callback e.g.

FutureBuilder(
  future: retrieveLocation(),
  builder: (context, AsyncSnapshot snapshot) {
    if (snapshot.data == null) {
      return Center(child: CircularProgressIndicator());
    }
    return Center(
    child: Container( 
      child: Column(
        children: <Widget> [
          Image.network(widget.post.data["image"]),
          Text(widget.post.data["wastedate"]), 
          Text(widget.post.data["wastenumber"]), 
          Text('Latitude: ${locationData.latitude}'),
          Text('Longitude: ${locationData.longitude}')

        ]
      )
    )
  },
);

问题是在完全执行 retrieveLocation()

这篇关于引发了另一个异常:NoSuchMethodError:在null上调用了getter'latitude'的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！