I'm developing a weather app using an API from OpenWeatherMap. Every time I try to run my code, the error late initialization pops up. I've tried adding the null safety check(!) in place of late but it's still the same. Any idea where I could have gone wrong? Any help would be deeply appreciated. A sample code for solving the error would help a lot. Thanks!!

The error I'm getting in the console:

Performing hot restart... 1,492ms Restarted application in 1,501ms. ══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════ The following LateError was thrown building: LateInitializationError: Field 'weatherInfo' has not been initialized.

When the exception was thrown, this was the stack: C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/internal/js_dev_runtime/private/ddc_runtime/errors.dart 251:49 throw packages/finalproject/LastProject/LastProject_Screen.dart 13:44 get weatherInfo packages/finalproject/LastProject/LastProject_Screen.dart 10:56 mainBodyWidget
packages/finalproject/LastProject/LastProject_Screen.dart 10:56 packages/flutter/src/widgets/sliver.dart 456:22 build packages/flutter/src/widgets/sliver.dart 1214:28 [_build]
packages/flutter/src/widgets/sliver.dart 1227:55 packages/flutter/src/widgets/framework.dart 2573:19 buildScope
packages/flutter/src/widgets/sliver.dart 1220:5 createChild
packages/flutter/src/rendering/sliver_multi_box_adaptor.dart 349:23 packages/flutter/src/scheduler/binding.dart 1080:9 handleDrawFrame packages/flutter/src/scheduler/binding.dart 863:7 C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/private/isolate_helper.dart 48:19 internalCallback

Note: This is just a part of the errors in the console because there are many.

The Code for UI:

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

import 'LastProject_model.dart';

class LastProjectScreen extends StatefulWidget {
  const LastProjectScreen({Key? key}) : super(key: key);

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

class _LastProjectScreenState extends State<LastProjectScreen> {

  //initializing model class object
  late WeatherInfo weatherInfo;
  TextEditingController _textEditingController = TextEditingController();

  //overriding initstate to parse the data and display it on the screen
  @override
  void initState() {
    super.initState();
  }


//data parsing function to call the data from the json file
  getData() async {
    http.Response jsondata = await http.get(Uri.parse(
        'https://api.openweathermap.org/data/2.5/forecast/daily?q=${_textEditingController.text}&units=metric&cnt=7&appid=3c044b7295d2df14f8bee74c19d4b96f'));
    print(jsondata.body);
    weatherInfo = WeatherInfo.fromJson(json.decode(jsondata.body));
    return weatherInfo;
  }


//first row of the screen
  Widget uirow1(WeatherInfo weatherInfo) {
    return Container(
      padding: EdgeInsets.all(5),
      margin: EdgeInsets.only(left: 20, right: 20, top: 20),
      decoration: BoxDecoration(
          // color: Colors.white,
          gradient: LinearGradient(
              colors: [Colors.blue.shade200, Colors.blue.shade50]),
          borderRadius: BorderRadius.all(Radius.circular(20)),
          boxShadow: [
            BoxShadow(
              color: Colors.grey.withOpacity(0.1),
              spreadRadius: 5,
              blurRadius: 7,
              offset: Offset(0, 3),
            )
          ]),
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: [
          Column(
            mainAxisAlignment: MainAxisAlignment.start,
            children: [
              Text(
                'name',
                // weatherInfo.city.name,
                style: TextStyle(fontSize: 17, fontWeight: FontWeight.w700),
              ),
              SizedBox(height: 5),
              Text('temp °F',
                  style: TextStyle(
                      fontSize: 20,
                      fontWeight: FontWeight.bold,
                      color: Colors.black)),
              SizedBox(height: 5),
              Text('description',
                  style: TextStyle(
                      fontSize: 15,
                      fontWeight: FontWeight.bold,
                      color: Colors.black))
            ],
          ),
          Icon(
            Icons.cloud,
            color: Colors.pink[400],
            size: 100,
          ),
        ],
      ),
    );
  }


//second row of the screen
  Widget uirow2() {
    return Container(
      padding: EdgeInsets.all(5),
      margin: EdgeInsets.all(20),
      decoration: BoxDecoration(
          // color: Colors.white,
          gradient: LinearGradient(
              colors: [Colors.blue.shade200, Colors.blue.shade50]),
          borderRadius: BorderRadius.all(Radius.circular(20)),
          boxShadow: [
            BoxShadow(
              color: Colors.grey.withOpacity(0.1),
              spreadRadius: 5,
              blurRadius: 7,
              offset: Offset(0, 3),
            )
          ]),
      child: Column(
        children: [
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceEvenly,
            children: [
              Text('windSpeed',
                  style: TextStyle(
                    fontSize: 15,
                  )),
              // SizedBox(width: 3),
              Text('humidity',
                  style: TextStyle(
                    fontSize: 15,
                  )),
              // SizedBox(width: 5),
              Text('°F',
                  style: TextStyle(
                    fontSize: 15,
                  )),
            ],
          ),
          Row(
            mainAxisAlignment: MainAxisAlignment.spaceEvenly,
            children: [
              Icon(Icons.air_outlined, color: Colors.grey[600], size: 25),
              // const SizedBox(width: 5),
              Icon(Icons.whatshot_rounded, color: Colors.grey[600], size: 25),
              // const SizedBox(width: 5),
              Icon(Icons.air_outlined, color: Colors.grey[600], size: 25)
            ],
          ),
        ],
      ),
    );
  }


//main body widget of the screen
  Widget mainBodyWidget(BuildContext context) {
    return
        // ListView(scrollDirection: Axis.vertical, children: [
        Container(
      padding: EdgeInsets.all(15),
      decoration: const BoxDecoration(
          image: DecorationImage(
              image: NetworkImage(
                  'https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSZCv1LyQUyAJQE21-uNUMx3S8ZgK2U9S--1wQB59QaTFHBp2VqxGTAen5FRA7m5h-E4OU&usqp=CAU'),
              fit: BoxFit.fill)),
      child: Column(
        children: [
          searchwidget(),
          const SizedBox(height: 15),
          uirow1(weatherInfo),
          const SizedBox(height: 15),
          uirow2(),
          const SizedBox(height: 15),
          uirow3()
        ],
      ),
    );
  }


//third row of the screen
  Widget uirow3() {
    return Container(
        padding: EdgeInsets.all(15),
        margin: EdgeInsets.only(left: 20, right: 20),
        height: 180,
        decoration: BoxDecoration(
            gradient: LinearGradient(
                colors: [Colors.blue.shade200, Colors.blue.shade50]),
            borderRadius: BorderRadius.all(Radius.circular(20)),
            boxShadow: [
              BoxShadow(
                color: Colors.grey.withOpacity(0.1),
                spreadRadius: 5,
                blurRadius: 7,
                offset: Offset(0, 3),
              )
            ]),
        child: ListView.separated(
            scrollDirection: Axis.horizontal,
            itemBuilder: (BuildContext context, int index) {
              return Container(
                child: uirow3data(),
              );
            },
            separatorBuilder: (BuildContext context, int index) {
              return SizedBox(width: 20);
            },
            itemCount: 7
            // weatherInfo.weatherListInfo.length,
            ));
  }

//data for the third row of the screen
  Widget uirow3data() {
    return Column(
      children: [
        Center(
            child: Text('Saturday',
                style: TextStyle(
                  fontWeight: FontWeight.bold,
                ))),
        SizedBox(height: 5),
        Icon(
          Icons.cloud,
          color: Colors.pink[400],
          size: 50,
        ),
        SizedBox(height: 4),
        Text('High: 71°F'),
        SizedBox(height: 3),
        Text('Low: 71°F'),
        SizedBox(height: 3),
        Text('Hum: 40%'),
        SizedBox(height: 3),
        Text('Win: 4 mi/h')
      ],
    );
  }

//search textfiled widget
  Widget searchwidget() {
    return Container(
      margin: EdgeInsets.only(left: 20, right: 20, top: 10),
      child: Center(
        child: TextField(
          controller: _textEditingController,
          decoration: InputDecoration(
              enabledBorder: OutlineInputBorder(
                  gapPadding: 3.0,
                  borderSide: const BorderSide(color: Colors.grey, width: 2.0),
                  borderRadius: BorderRadius.circular(11)),
              hintText: 'Search',
              hintStyle: const TextStyle(color: Colors.grey),
              prefixIcon: const Icon(
                Icons.search_sharp,
                color: Colors.grey,
              ),
              suffixIcon: InkWell(
                child: const Icon(Icons.navigate_next, color: Colors.grey),
                onTap: () => getData(),
              )),
        ),
      ),
    );
  }

//main container widget
  Widget mainContainerWidget(BuildContext context) {
    return Scaffold(
        body: FutureBuilder(
                future: getData(),
                builder: (context, snapshot) {
                  if (snapshot.hasError) {
                    return Center(child: Text("Couldn't load the data"));
                  }
                  if (snapshot.hasData) {
                    return Text("Data is being processed");
                  }
                  if (snapshot.data == null) {
                    return ListView.builder(
                        scrollDirection: Axis.vertical,
                        itemCount: 1,
                        shrinkWrap: true,
                        itemBuilder: (context, index) {
                          return Column(
                            children: [mainBodyWidget(context)],
                          );
                        });
                  }
                  return CircularProgressIndicator();
                }));
  }

//Main build function
  @override
  Widget build(BuildContext context) {
    return mainContainerWidget(context);
  }
}

The Code for Model class:

class WeatherInfo {
  late CityInfo city;
  late String cod;
  late double message;
  late int cnt;
  late List<WeatherListInfo> weatherListInfo;

  WeatherInfo(
      this.city, this.cod, this.message, this.cnt, this.weatherListInfo);

  factory WeatherInfo.fromJson(Map<String, dynamic> json) {
    return WeatherInfo(
        CityInfo.fromJson(json["city"]),
        json["cod"],
        json["message"],
        json["cnt"],
        (json["list"] as List).map((e) => WeatherListInfo.fromJson(e)).toList());
  }
}

class CityInfo {
  late String id;
  late String name;
  late String country;
  late String population;
  late String timezone;

  CityInfo(this.id, this.name, this.country, this.population, this.timezone);

  factory CityInfo.fromJson(Map<String, dynamic> json) {
    return CityInfo(json["id"].toString(), json["name"], json["country"],
        json["population"].toString(), json["timezone"].toString());
  }
}

class WeatherListInfo {
  late String dt;
  late String sunrise;
  late String sunset;
  late TemperatureListInfo temperatureListInfo;
  late String pressure;
  late String humidity;
  late List<WeatherDetailInfo> weatherDetailInfo;
  late FeelsLikeListInfo feelsLikeInfo;
  late String speed;
  late String deg;
  late String gust;
  late String clouds;
  late String pop;
  late String rain;

  WeatherListInfo(
    this.dt,
    this.sunrise,
    this.sunset,
    this.temperatureListInfo,
    this.pressure,
    this.humidity,
    this.weatherDetailInfo,
    this.feelsLikeInfo,
    this.speed,
    this.deg,
    this.gust,
    this.clouds,
    this.pop,
    this.rain,
  );

  factory WeatherListInfo.fromJson(Map<String, dynamic> json) {
    return WeatherListInfo(
      json["dt"].toString(),
      json["sunrise"].toString(),
      json["sunset"].toString(),
      TemperatureListInfo.fromJson(json["temp"]),
      json["pressure"].toString(),
      json["humidity"].toString(),
      (json["weather"] as List).map((e) => WeatherDetailInfo.fromJson(e)).toList(),
      FeelsLikeListInfo.fromJson(json["feels_like"]),
      json["speed"].toString(),
      json["deg"].toString(),
      json["gust"].toString(),
      json["clouds"].toString(),
      json["pop"].toString(),
      json["rain"].toString(),
    );
  }
}

class TemperatureListInfo {
  late String day;
  late String min;
  late String max;
  late String night;
  late String eve;
  late String morn;

  TemperatureListInfo(
      this.day, this.night, this.eve, this.morn, this.min, this.max);

  factory TemperatureListInfo.fromJson(Map<String, dynamic> json) {
    return TemperatureListInfo(
      json["day"].toString(),
      json["night"].toString(),
      json["eve"].toString(),
      json["morn"].toString(),
      json["min"].toString(),
      json["max"].toString(),
    );
  }
}

class FeelsLikeListInfo {
  late String day;
  late String night;
  late String eve;
  late String morn;

  FeelsLikeListInfo(this.day, this.night, this.eve, this.morn);

  factory FeelsLikeListInfo.fromJson(Map<String, dynamic> json) {
    return FeelsLikeListInfo(
      json["day"].toString(),
      json["night"].toString(),
      json["eve"].toString(),
      json["morn"].toString(),
    );
  }
}

class WeatherDetailInfo {
  late String id;
  late String main;
  late String description;
  late String icon;

  WeatherDetailInfo(this.id, this.main, this.description, this.icon);

  factory WeatherDetailInfo.fromJson(Map<String, dynamic> json) {
    return WeatherDetailInfo(
      json["id"].toString(),
      json["main"],
      json["description"],
      json["icon"],
    );
  }
}

CodePudding user response：

The error message says it, you didn't initialize weatherInfo. When you mark a variable as late you must initialize it later, but in your case, you only initialize it when you call getData(), so ui complains because it uses a variable that is not yet initialized. You have to options here,

first: you call getData in initState, so the variable will be initialized.

or, second: you remove the late keyword and make the object nullable, but now you'll have to add null checks all over the code.

CodePudding user response：

In your main.dart add .

void main()async{
 WidgetsFlutterBinding.ensureInitialized();

 runApp(MyApp());
}