Usamos o modelo MVC

get_anuncios.dart

import 'dart:convert';
import 'package:facil_alimentos/api/services_api/cache_management.dart';
import 'package:facil_alimentos/models/anuncios_model.dart';
import 'package:http/http.dart' as http;

class GetAnunciosApi {
  int qtdPatronizedPref = 0;
  int qtdPatronized = 0;
  int qtdNotPatronized = 0;
  int qtdLastPosts = 0;

  Future<List<AnuncioModel>> getMyAnuncios(String userId) async {
    List<AnuncioModel> anuncios = [];
    var url =
        'xxxxxxxxxxxxxxxxxxxxxxxxxx';

    var header = {
      "Content-type": "application/json",
      "key": "xxxxxxxxxxxxxxxx",
      "token": "xxxxxxxxxxxxxxxxxxxxxxxxxxx"
    };

    Map params = {
      "user_id": int.parse(userId),
    };

    var _body = json.encode(params);

    try {
      var response = await http.post(url, headers: header, body: _body);

      final data = json.decode(response.body);

      if (data['status'] == '400') {
        return anuncios;
      }

      for (Map map in data['data']) {
        AnuncioModel anuncio = AnuncioModel.fromJson(map);
        anuncios.add(anuncio);
      }

      return anuncios;
    } catch (e) {
      return null;
    }
  }