Hi i am working on a weather app i learnt from a course, everything was working fine till i start with the refactoring and it just got complicated the code show no error but when i hot restart the app it crash showing

The method '[]' was called on null.
Receiver: null
Tried calling: []("main")

in the console

i don't even know where i went wrong with my code and i will like if someone can take a lot at the code below and how i can fix it: networking.dart

import 'package:http/http.dart' as http;
import 'dart:convert';

class NetworkHelper {
  NetworkHelper(this.url);
  final String url;

  Future getData() async {
    http.Response response = await http.get(Uri.parse(url));
    if (response.statusCode == 200) {
      String data = response.body;
      var output = jsonDecode(data);
    } else {
      print(response.statusCode);
      print('not working');
    }
  }
}

loading_screen.dart

import 'package:flutter/animation.dart';
import 'package:flutter/material.dart';
import 'package:clima/services/location.dart';
import 'package:clima/services/networking.dart';
import 'package:clima/screens/location_screen.dart';
import 'package:flutter_spinkit/flutter_spinkit.dart';

const apiKey = '4c6ffd8e4e647128123739045f48d839';

class LoadingScreen extends StatefulWidget {
  @override
  _LoadingScreenState createState() => _LoadingScreenState();
}

class _LoadingScreenState extends State<LoadingScreen> {
  @override
  double? latitude;
  double? longtitude;
  void initState() {
    super.initState();
    getLocationData();
  }

  void getLocationData() async {
    Location location = Location();
    await location.geolocation();
    latitude = location.latitude;
    longtitude = location.longtitude;
    NetworkHelper networkHelper = NetworkHelper(
        'https://api.openweathermap.org/data/2.5/weather?lat=$latitude&lon=$longtitude&appid=$apiKey&units=metric');
    var weatherdata = await networkHelper.getData();
    Navigator.push(context, MaterialPageRoute(builder: (context) {
      return LocationScreen(
        locationWeather: weatherdata,
      );
    }));
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: SpinKitDoubleBounce(
          color: Colors.white,
          size: 100.0,
        ),
      ),
    );
  }
}

location_screen.dart

import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:clima/utilities/constants.dart';
import 'package:clima/services/weather.dart';

class LocationScreen extends StatefulWidget {
  final locationWeather;
  LocationScreen({this.locationWeather});
  @override
  _LocationScreenState createState() => _LocationScreenState();
}

class _LocationScreenState extends State<LocationScreen> {
  WeatherModel weather = WeatherModel();
  int? temperature;
  String? weatherIcon;
  String? cityName;
  String? weatherMessage;
  @override
  void initState() {
    UpdateUi(widget.locationWeather);
    super.initState();
  }

  void UpdateUi(dynamic weatherData) {
    setState(() {
      double temp = weatherData['main']['temp'];
      temperature = temp.toInt();
      var condition = weatherData['weather'][0]['id '];
      cityName = weatherData['name'];
      weatherMessage = weather.getMessage(temperature!);
      weatherIcon = weather.getWeatherIcon(condition);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        decoration: BoxDecoration(
          image: DecorationImage(
            image: AssetImage('images/location_background.jpg'),
            fit: BoxFit.cover,
            colorFilter: ColorFilter.mode(
                Colors.white.withOpacity(0.8), BlendMode.dstATop),
          ),
        ),
        constraints: BoxConstraints.expand(),
        child: SafeArea(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: <Widget>[
              Row(
                mainAxisAlignment: MainAxisAlignment.spaceBetween,
                children: <Widget>[
                  FlatButton(
                    onPressed: () {},
                    child: Icon(
                      Icons.near_me,
                      size: 50.0,
                    ),
                  ),
                  FlatButton(
                    onPressed: () {},
                    child: Icon(
                      Icons.location_city,
                      size: 50.0,
                    ),
                  ),
                ],
              ),
              Padding(
                padding: EdgeInsets.only(left: 15.0),
                child: Row(
                  children: <Widget>[
                    Text(
                      weatherIcon!,
                      style: kTempTextStyle,
                    ),
                    Text(
                      '☀️',
                      style: kConditionTextStyle,
                    ),
                  ],
                ),
              ),
              Padding(
                padding: EdgeInsets.only(right: 15.0),
                child: Text(
                  "$weatherMessage in $cityName",
                  textAlign: TextAlign.right,
                  style: kMessageTextStyle,
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

this is the part from the location_screen.dart where i think i made a mistake i tried using jsonDecode(data) to see if that will fix it, but it did not, because i have already declared it somewhere else before :

void UpdateUi(dynamic weatherData) {
    setState(() {
      double temp = weatherData['main']['temp'];
      temperature = temp.toInt();
      var condition = weatherData['weather'][0]['id '];
      cityName = weatherData['name'];
      weatherMessage = weather.getMessage(temperature!);
      weatherIcon = weather.getWeatherIcon(condition);
    });
  }

I tried fixing it , but it did not work , i am actually a beginner on flutter, i think that is the reason why i am having this ,

so i will like someone to lead me on the right path..just incase if i encounter such in the future i can fix it myself thanks.

CodePudding user response：

The Error comes from location_screen.dart line 27. I cannot really tell the nature of what the API request is sending back. I may be null, that try when you tried to call weatherData['main']['temp'] you got an error.

Check your internet connection and the terminal for any errors. Your implementation seems okay.

CodePudding user response：

Try to remove the empty space after id in var condition