Flutter Unhandled Exception: DioError [DioErrorType.DEFAULT]: NoSuchMethodError: The getter 'statusCode' was called on null

Question

In flutter I am trying to call and Endpoint that returns and object like this:

{
  "latestVersion": "1.0.2",
  "minVersion": "1.0.1"
}

I am getting this error:

I/flutter (17425): checkLatestVersion
I/flutter (17425): provider
I/flutter (17425): http://10.0.2.2:3000/api
E/flutter (17425): [ERROR:flutter/lib/ui/ui_dart_state.cc(177)] Unhandled Exception: DioError [DioErrorType.DEFAULT]: NoSuchMethodError: The getter 'statusCode' was called on null.
E/flutter (17425): Receiver: null
E/flutter (17425): Tried calling: statusCode
E/flutter (17425): #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
E/flutter (17425): #1      errorInterceptor (package:kliik_app/dio/interceptor.dart:23:25)
E/flutter (17425): #2      addInterceptors.<anonymous closure> (package:kliik_app/dio/interceptor.dart:19:39)
E/flutter (17425): #3      InterceptorsWrapper.onError (package:dio/src/interceptor.dart:125:22)

I don't understand why the call isn't performed. The problem is when I do the call:

var res = await _dio.get(_endpoint+"/app-version");

It seems like res is null or it doesn't do the get call, but I don't understand why.

Thats part of my code:

class _UpdateAppState extends State<UpdateApp> {
  final AppVersionApiProvider _provider = new AppVersionApiProvider();

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

    checkLatestVersion(context);
  }

  Future  checkLatestVersion(context) async {
    await Future.delayed(Duration(seconds: 5));
    print("checkLatestVersion");
    final AppVersionModel appVersion = await _provider.find();
    print("afterCallProvider");
    if (appVersion != null) {

      PackageInfo packageInfo = await PackageInfo.fromPlatform();
      Version currentVersion = Version.parse(packageInfo.version);

      if (appVersion.minVersion > currentVersion) {
        _showCompulsoryUpdateDialog(
          context,
          "Siusplau, actualitza l'app per continuar.",
        );
      } else if (appVersion.latestVersion > currentVersion) {
        SharedPreferences sharedPreferences =
            await SharedPreferences.getInstance();

        bool showUpdates = false;
        showUpdates = sharedPreferences.getBool(kUpdateDialogKeyName);
        if (showUpdates != null && showUpdates == false) {
          return;
        }

        _showOptionalUpdateDialog(
          context,
          "Hi ha una nova versió de l'app disponible. Vols actualitzar-la?",
        );
        print('Update available');
      } else {
        print('App is up to date');
      }
    }
  }

Provider class: await _provider.find()

class AppVersionApiProvider {
  final String _endpoint = conf.api;
  final Dio _dio = addInterceptors(Dio());

  Future<AppVersionModel> find() async {
     print("provider");
     print(_endpoint);
     var res = await _dio.get(_endpoint+"/app-version");
    
    if(res.statusCode == 200) {
      print("test");
      return AppVersionModel.fromJson(res.data);
    }
    return null;
  }
}

Backend API:

import { Controller, Get } from '@nestjs/common';
import { AppVersionService } from './app-version.service';

@Controller('app-version')
export class AppVersionController {

  constructor(
    private appVersionService: AppVersionService
  ) { }

  @Get('/')
  async appVersion() {
    console.log("app-versiooooon");
    return this.appVersionService.get();
  }
}

The API works fine, I open the Google Chrome and I go to:

http://localhost:3000/api/app-version

It returns:

// 20201123095650
// http://localhost:3000/api/app-version
​
{
  "latestVersion": "1.0.2",
  "minVersion": "1.0.1"
}

Solution

final Dio _dio = addInterceptors(Dio());

var res = await _dio.get(_endpoint+"/app-version");

Change to:

final Dio _dio = new Dio();

Response res = await _dio.get(_endpoint+"/app-version");

Comments

[Arnau Bosch]

@Vinah H P I have tried what you said: I am getting the same error: [ERROR:flutter/lib/ui/ui_dart_state.cc(177)] Unhandled Exception: DioError [DioErrorType.DEFAULT]: NoSuchMethodError: The getter 'statusCode' was called on null. E/flutter (28532): Receiver: null E/flutter (28532): Tried calling: statusCode Also it says <asynchronous suspension>

[Arnau Bosch]

@Vinah H P Hi, It doesn't print nothing. I think that the problem is with the call await _dio.get(_endpoint+"/app-version");

[Admin]

Response res = await _dio.get(_endpoint+"/app-version"); print(res.statusCode); Tell me what you get..

[Arnau Bosch]

Vinay H P this: [ERROR:flutter/lib/ui/ui_dart_state.cc(177)] Unhandled Exception: DioError [DioErrorType.DEFAULT]: NoSuchMethodError: The getter 'statusCode' was called on null. E/flutter (30618): Receiver: null E/flutter (30618): Tried calling: statusCode

[Admin]

@Arnau final Dio _dio = new Dio(); Try without addInterceptors(Dio()); Lets debug one step at a time. I assume you are using Android Studio, This Package pub.dev/packages/dio.. and Android Studio Emulator.

[Admin]

@Arnau <asynchronous suspension> is not an indication of a problem, it just indicates that code execution is not synchronous code executed line-by-line, but instead a callback from a completed Future started at some position in the callstack.

[Admin]

@ArnauBoschTekla.io medium.com/flutter-community/…

[Arnau Bosch]

yeah it was that. I have remove addIntercepetors(Dio()) and now it works! I dont understand why but thank you

[Admin]

Hi @Arnau Bosch, Just a request. I need reputation points so if you could vote and select this answer as accepted answer, I will get some. I am new, trying to answer the questions and help others. So, please help me by doing that.