1. Package

add http package in pubspec.xml

                     dependencies:
                              flutter:
                              http: 
                      

2. constants

util/constants.dart

                      const urlBase = 'https://reqres.in/api/';
                      const urlLogin = 'login';
                      const urlUserList = 'users?page=1';

                      

3. Service

lib/apis/request.dart

import http package

                      import 'package:http/http.dart' as http;
                      

define class and constructor

                      class Request {
                          final String url;
                          final dynamic body;

                          Request({this.url, this.body});


                      }
                    

Define functions

                    Future<http.Response> post() {
                         return http.post(urlBase + url, body: body).timeout(Duration(minutes: 2));
                    }
                    Future<http.Response> get() {
                        return http.get(urlBase + url).timeout(Duration(minutes: 2));
                    }

                  

complete code

                  import 'package:flutter_api_calling_using_getx/util/constants.dart';
                  import 'package:http/http.dart' as http;

                  class Request {
                    final String url;
                    final dynamic body;

                    Request({this.url, this.body});

                    Future<http.Response> post() {
                      return http.post(urlBase + url, body: body).timeout(Duration(minutes: 2));
                    }
                    Future<http.Response> get() {
                      return http.get(urlBase + url).timeout(Duration(minutes: 2));
                    }
                  }

                  

4. controller

                  <p>controllers/login_controller.dart</p>
                  <p>define class</p>
                  <pre><xmp>
                  class LoginController extends GetxController {

                  }  
                  

declare the variable for form fields

                  TextEditingController emailTextController;
                  TextEditingController passwordTextController;
                  

assign the controller

                  @override
                  void onInit() {
                    emailTextController = TextEditingController();
                    passwordTextController = TextEditingController();
                    super.onInit();
                  }

                

define apilogin()

                void apiLogin() async {
                  Get.dialog(Center(child: CircularProgressIndicator()),
                      barrierDismissible: false);
                  Request request = Request(url: urlLogin, body: {
                    'email': emailTextController.text,
                    'password': passwordTextController.text
                  });
                  request.post().then((value) {
                    Get.back();
                    Get.off(() => HomeScreen());
                    print(value.body);
                  }).catchError((onError) {});
                }

              

Complete code

              import 'package:flutter/material.dart';
import 'package:flutter_api_calling_using_getx/apis/request.dart';
import 'package:flutter_api_calling_using_getx/screens/home_screen.dart';
import 'package:flutter_api_calling_using_getx/util/constants.dart';
import 'package:get/get.dart';

class LoginController extends GetxController {

  TextEditingController emailTextController;
  TextEditingController passwordTextController;

  @override
  void onInit() {
    emailTextController = TextEditingController();
    passwordTextController = TextEditingController();
    super.onInit();
  }

  void apiLogin() async {
    Get.dialog(Center(child: CircularProgressIndicator()),
        barrierDismissible: false);
    Request request = Request(url: urlLogin, body: {
      'email': emailTextController.text,
      'password': passwordTextController.text
    });
    request.post().then((value) {
      Get.back();
      Get.off(() => HomeScreen());
      print(value.body);
    }).catchError((onError) {});
  }

  @override
  void onClose() {
    emailTextController?.dispose();
    passwordTextController?.dispose();
    super.onClose();
  }
}

5. Screen

screens/login_screen.dart

create class

class LoginScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {

  }
}

login controller

import 'package:flutter_api_calling_using_getx/core/controllers/login_controllers.dart';

class LoginScreen extends StatelessWidget {
    final LoginController _loginController = Get.put(LoginController());

}

Complete code

import 'package:flutter/material.dart';
import 'package:flutter_api_calling_using_getx/common_components/default_button.dart';
import 'package:flutter_api_calling_using_getx/core/controllers/login_controllers.dart';
import 'package:get/get.dart';
import 'package:google_fonts/google_fonts.dart';

class LoginScreen extends StatelessWidget {
  static String routeName = "/login_screen";

  final LoginController _loginController = Get.put(LoginController());
  final _formKey = GlobalKey<FormState>();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.white,
      appBar: AppBar(
        title: Text(
          'GetX Login',
        ),
      ),
      body: Container(
        padding: EdgeInsets.all(16),
        child: Form(
          key: _formKey,
          child: Column(
            children: <Widget>[
              TextFormField(
                controller: _loginController.emailTextController,
                keyboardType: TextInputType.emailAddress,
                decoration: InputDecoration(
                  fillColor: Colors.grey[200],
                  filled: true,
                  hintText: 'Email',
                  hintStyle: GoogleFonts.exo2(
                    fontSize: 16,
                    color: Colors.grey,
                    fontWeight: FontWeight.normal,
                  ),
                  border: OutlineInputBorder(
                    borderRadius: BorderRadius.circular(10),
                    borderSide: BorderSide(
                      color: Colors.transparent,
                      width: 0,
                    ),
                  ),
                  enabledBorder: OutlineInputBorder(
                    borderRadius: BorderRadius.circular(10),
                    borderSide: BorderSide(
                      color: Colors.transparent,
                      width: 0,
                    ),
                  ),
                ),
                style: GoogleFonts.exo2(
                  fontSize: 16,
                  color: Colors.black,
                  fontWeight: FontWeight.normal,
                ),
                validator: (value) =>
                    value.trim().isEmpty ? 'Email required' : null,
              ),
              SizedBox(height: 16),
              TextFormField(
                controller: _loginController.passwordTextController,
                keyboardType: TextInputType.text,
                obscureText: true,
                decoration: InputDecoration(
                  fillColor: Colors.grey[200],
                  filled: true,
                  hintText: 'Password',
                  hintStyle: GoogleFonts.exo2(
                    fontSize: 16,
                    color: Colors.grey,
                    fontWeight: FontWeight.normal,
                  ),
                  border: OutlineInputBorder(
                    borderRadius: BorderRadius.circular(10),
                    borderSide: BorderSide(
                      color: Colors.transparent,
                      width: 0,
                    ),
                  ),
                  enabledBorder: OutlineInputBorder(
                    borderRadius: BorderRadius.circular(10),
                    borderSide: BorderSide(
                      color: Colors.transparent,
                      width: 0,
                    ),
                  ),
                ),
                validator: (value) =>
                    value.trim().isEmpty ? 'Password required' : null,
                style: GoogleFonts.exo2(
                  fontSize: 16,
                  color: Colors.black,
                  fontWeight: FontWeight.normal,
                ),
              ),
              SizedBox(height: 16),
              DefaultButton(
                  text: 'Login',
                  press: () {
                    if (_formKey.currentState.validate()) {
                      _loginController.apiLogin();
                    }
                  })
            ],
          ),
        ),
      ),
    );
  }
}