controller.dart

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

class PostController extends GetxController {
  final _postList = <PostModel>[].obs;
  List<PostModel> get postList => _postList.value;

  final _isLoading = false.obs;
  bool get isLoading => _isLoading.value;

  Future<void> getResults() async {
    _isLoading.value = true;
    var response = await http.get('https://jsonplaceholder.typicode.com/posts');
    var responseList = (jsonDecode(response.body) as List)
        .map((e) => PostModel.fromJson(e))
        .toList();
    // auto refresh the UI... but still LOADING.
    _postList.value = responseList;
    _isLoading.value = false;
  }
}

main.dart

import 'package:flutter/material.dart';
import 'package:get/get.dart';
import 'controller.dart';
import 'post_page.dart';

void main() {
  Get.put(PostController());
  runApp(MaterialApp(
    debugShowCheckedModeBanner: false,
    home: PostPage(),
  ));
}

model.dart

// MODEL
class PostModel {
  int userId;
  int id;
  String title;
  String body;

  PostModel({this.userId, this.id, this.title, this.body});

  PostModel.fromJson(Map<String, dynamic> json) {
    userId = json['userId'];
    id = json['id'];
    title = json['title'];
    body = json['body'];
  }
}

post_page.dart

import 'package:flutter/material.dart';
import 'package:get/get.dart';

import 'controller.dart';

class PostPage extends GetView<PostController> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text('Posts')),
      body: GetX(
        init: controller,
        initState: (_) {
          controller.getResults();
        },
        builder: (_) {
          if (controller.isLoading) {
            return Center(
              child: Text('Loading...'),
            );
          }
          final postList = controller.postList;
          if (postList.isEmpty) {
            return Center(
              child: Text('No content to display'),
            );
          }

          // build the list.
          return ListView.builder(
            itemBuilder: (ctx, idx) {
              final postItem = postList[idx];
              return ListTile(
                contentPadding: EdgeInsets.all(12),
                title: Text(postItem.title),
                subtitle: Text(postItem.body),
              );
            },
            itemCount: postList.length,
          );
        },
      ),
    );
  }
}