Unhandled Exception: NoSuchMethodError: The method '[]' was called on null (json parse)

Just Check the modified code :

Following is the local json that you provided:

{ "Delhi": { "districtData": { "East Delhi": { "confirmed": 1, "lastupdatedtime": "" }, "South West Delhi": { "confirmed": 3, "lastupdatedtime": "" }, "West Delhi": { "confirmed": 2, "lastupdatedtime": "" }, "North Delhi": { "confirmed": 3, "lastupdatedtime": "" }, "New Delhi": { "confirmed": 3, "lastupdatedtime": "" }, "South Delhi": { "confirmed": 2, "lastupdatedtime": "" }, "North East Delhi": { "confirmed": 1, "lastupdatedtime": "" }, "North West Delhi": { "confirmed": 3, "lastupdatedtime": "" }, "Unknown": { "confirmed": 53, "lastupdatedtime": "" }, "Delhi": { "confirmed": 1, "lastupdatedtime": "" } } } } 

Later i have created a model class for that :

// To parse this JSON data, do // // final indiaState = indiaStateFromJson(jsonString); import 'dart:convert'; IndiaState indiaStateFromJson(String str) => IndiaState.fromJson(json.decode(str)); String indiaStateToJson(IndiaState data) => json.encode(data.toJson()); class IndiaState { Delhi delhi; IndiaState({ this.delhi, }); factory IndiaState.fromJson(Map<String, dynamic> json) => IndiaState( delhi: Delhi.fromJson(json["Delhi"]), ); Map<String, dynamic> toJson() => { "Delhi": delhi.toJson(), }; } class Delhi { Map<String, DistrictDatum> districtData; Delhi({ this.districtData, }); factory Delhi.fromJson(Map<String, dynamic> json) => Delhi( districtData: Map.from(json["districtData"]).map((k, v) => MapEntry<String, DistrictDatum>(k, DistrictDatum.fromJson(v))), ); Map<String, dynamic> toJson() => { "districtData": Map.from(districtData).map((k, v) => MapEntry<String, dynamic>(k, v.toJson())), }; } class DistrictDatum { int confirmed; String lastupdatedtime; DistrictDatum({ this.confirmed, this.lastupdatedtime, }); factory DistrictDatum.fromJson(Map<String, dynamic> json) => DistrictDatum( confirmed: json["confirmed"], lastupdatedtime: json["lastupdatedtime"], ); Map<String, dynamic> toJson() => { "confirmed": confirmed, "lastupdatedtime": lastupdatedtime, }; } 

below is the main file i have shown your data in a listview check it out :

import 'package:flutter/material.dart'; import 'package:flutter/services.dart'; import 'package:sample_project_for_api/model.dart'; class HomePage extends StatefulWidget { @override _HomePageState createState() => _HomePageState(); } class _HomePageState extends State<HomePage> { bool isLoading = false; List<Cities> citilesList = List(); // here i have taken the json locally which you posted on stack Future<String> loadFromAssets() async { return await rootBundle.loadString('json/parse.json'); } @override void initState() { super.initState(); givenFunction(); } Future givenFunction() async { setState(() { isLoading = true; }); //final httpRequest = await http.get(districtAPI); //final json = jsonDecode(httpRequest.body); // you can make the http call above just uncomment is and comment the below line String jsonString = await loadFromAssets(); // Here you can just replace down your httpRequest.body with jsonString final indiaState = indiaStateFromJson(jsonString); indiaState.delhi.districtData.forEach((key, value) { // This column is show you the values are getting fetched and printed below print('This is the key : ' + key); print('Confirmed :' + value.confirmed.toString()); citilesList.add(Cities(key, value.confirmed)); }); setState(() { isLoading = false; }); } @override Widget build(BuildContext context) { return MaterialApp( home: Scaffold( body: isLoading ? CircularProgressIndicator() : ListView.builder( itemCount: citilesList.length, itemBuilder: (BuildContext context, int index) { return Container( child: Card( margin: EdgeInsets.symmetric(vertical: 10, horizontal: 10), child: Padding( padding: const EdgeInsets.all(15.0), child: Row( children: <Widget>[ Text(citilesList[index].state + ": "), Text(citilesList[index].confirmed.toString()) ], ), ), ), ); }, ), ), ); } } void main() { runApp(HomePage()); } class Cities { final String state; final int confirmed; Cities(this.state, this.confirmed); } 

Just added a sample image for the data fetch items: Let me know if it works