swagger/lib/token.dart

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

class TokenPage extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return _TokenPageState();
  }
}

class _TokenPageState extends State<TokenPage> {

  TextEditingController usernameController = TextEditingController();
  TextEditingController  passwordController = TextEditingController();

Future<String> authorization() async {
    var request = http.MultipartRequest(
        'GET', Uri.parse('http://localhost:8080/api/v1/projects'));
    request.fields.addAll({
      'grant_type': 'info',
      'client_id': 'info',
      'username': usernameController.text, 
      'password': passwordController.text, 
    });


    http.StreamedResponse response = await request.send();

    if (response.statusCode == 200) {
      Map<String, dynamic> auth =
          jsonDecode(await response.stream.bytesToString());

      return auth['access_token'];
    } else {
      return "";
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Login'),
        backgroundColor: Colors.green,
      ),
      body: Column(
        children: [
          Padding(
            padding: EdgeInsets.all(8.0),
            child: TextField(
              decoration: InputDecoration(labelText: 'username'),
              controller: usernameController,
            ),
          ),
          Padding(
            padding: EdgeInsets.all(8.0),
            child: TextField(
              decoration: InputDecoration(labelText: 'password'),
              controller: passwordController,
            ),
          ),          
          ElevatedButton(
            onPressed: () async {
              String token = await authorization();
              print(token); //This will be your token.
            },
            child: Text('Login'),),
        ],
      ),
    );
  }
}