Flutter get Json and extract variable

Question

Im newbie to dart/flutter.

I wrote a code that takes values from input fields and substitutes a link in url to check authorization and returns the following response:

  "result": {
    "Result": 0,
    "RequiredInfo": 0,
    "Custom": {},
    "Name": "1",
    "UserId": 4,
    "AuthenticationType": "",
    "Role": 1,
    "Claims": [
      {
        "type": "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name",
        "value": "1"
      }
    ]
  },
  "httpStatusCode": 200
}

I wrote the code in button method,

import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:convert';
import 'package:ultra/widgets/data/login_user.dart';

final loginUserText = TextEditingController();
final passwordUserText = TextEditingController();
const String login = '1';
const String pass = '1';
final String basicAuth = 'Basic ' + base64Encode(utf8.encode('$login:$pass'));

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

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

class InputFieldsState extends State<InputFields> {
  @override
  Widget build(BuildContext context) {
    return Container(
      width: 350,
      child: Column(
        children: [
          LoginFieldWidget(loginUserText: loginUserText),
          SizedBox(
            height: 15,
          ),
          PasswordFieldWidget(passwordUserText: passwordUserText),
          ButtonWidget(),
        ],
      ),
    );
  }
}

///////////////////////////// MAIN BUTTON ////////////////////////////////////
class ButtonWidget extends StatefulWidget {
  const ButtonWidget({
    Key? key,
  }) : super(key: key);

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

class _ButtonWidgetState extends State<ButtonWidget> {
  @override
  Widget build(BuildContext context) {
    //////////////// SHOW DIALOG ERROR WINDOW /////////////////////////////////
    Future<void> _showMyDialog() async {
      return showDialog<void>(
        context: context,
        barrierDismissible: false, // user must tap button!
        builder: (BuildContext context) {
          return AlertDialog(
            shape: RoundedRectangleBorder(
              borderRadius: BorderRadius.circular(15),
            ),
            title: const Text(
              'Ошибка',
              style: TextStyle(color: Colors.red),
            ),
            content: SingleChildScrollView(
              child: ListBody(
                children: const <Widget>[
                  Text(
                    'Вы ввели неправильный логин или пароль.',
                    style: TextStyle(fontSize: 18, fontWeight: FontWeight.w600),
                  ),
                  SizedBox(
                    height: 15,
                  ),
                  Text(''),
                ],
              ),
            ),
            actions: <Widget>[
              TextButton(
                child: const Text(
                  'OK',
                  style: TextStyle(fontSize: 28, color: Colors.red),
                ),
                onPressed: () {
                  Navigator.of(context).pop();
                },
              ),
            ],
          );
        },
      );
    }

//////////////////////////// AUTH FUNCTION ////////////////////////////////

    Future<dynamic> fetchData() async {
      final loginUser = loginUserText.text;
      final passUser = passwordUserText.text;
      final url = Uri.parse(
          'http://xx.xxx.xxx.xxx/api/users/$loginUser/$passUser/valid');
      final response = await http
          .get(url, headers: <String, String>{'authorization': basicAuth});
      Map<String, dynamic> parsed = json.decode(response.body);
      final user = User.fromJson(parsed);

      if (user.httpStatusCode == 200 && user.result!.result == 0) {
        Navigator.of(context).pushNamed('/main_screen');
      } else {
        _showMyDialog();
      }
    }

/////////////////////// ENTER BUTTON ////////////////////////////////////
    return Container(
      margin: EdgeInsets.only(top: 15),
      width: 250,
      height: 50,
      child: ElevatedButton(
        style: ButtonStyle(
          shape: MaterialStateProperty.all<RoundedRectangleBorder>(
            RoundedRectangleBorder(
              borderRadius: BorderRadius.circular(15),
              side: BorderSide(color: Colors.red),
            ),
          ),
          backgroundColor: MaterialStateProperty.all(Colors.red),
        ),
        onPressed: () {
          setState(() {
            fetchData();
          });
        },
        child: Text(
          'ВОЙТИ',
          style: TextStyle(fontSize: 20),
        ),
      ),
    );
  }
}

////////////////////////// PASSWORD FIELD //////////////////////////////////
class PasswordFieldWidget extends StatelessWidget {
  const PasswordFieldWidget({
    Key? key,
    required this.passwordUserText,
  }) : super(key: key);

  final TextEditingController passwordUserText;

  @override
  Widget build(BuildContext context) {
    return TextField(
      controller: passwordUserText,
      cursorColor: Colors.red,
      cursorHeight: 25,
      style: TextStyle(fontSize: 20),
      obscureText: true,
      decoration: InputDecoration(
          contentPadding: EdgeInsets.all(20),
          hintText: 'Пароль',
          hintStyle: TextStyle(fontSize: 20),
          prefixIcon: Icon(
            Icons.security,
            color: Colors.red,
          ),
          border: OutlineInputBorder(
            borderSide: BorderSide.none,
            borderRadius: const BorderRadius.all(
              Radius.circular(15),
            ),
          ),
          filled: true,
          fillColor: Colors.white),
    );
  }
}

/////////////////////////// LOGIN FIELD /////////////////////////////////////
class LoginFieldWidget extends StatelessWidget {

It seems to work fine, but I cannot figure out how I can get the UserId variable from the json request so that I can use it in other screen or widgets for other json requests, where the UserId of the user is already required.

Faizan Darwesh · Accepted Answer · 2021-08-08 06:51:54Z

1

final user = User.fromJson(parsed);

You can get UserId by using this code below

final userId = user.result!.UserId;

answered Aug 8, 2021 at 6:51

Faizan Darwesh

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2 Comments

Чак Джонс Over a year ago

I know this, thanks. When I do this, I cannot use that variable in other places, like screens or other widgets. I mean I cannot use this variable outside this method.

Faizan Darwesh Over a year ago

Your welcome. You can make userId variable global and assign it inside the function. Inorder to pass it to other widgets you can pass it as constructor parameter

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