Conversor_API_Flutter

// MODEL:
import 'dart:convert';

import 'package:http/http.dart';

class MoedaModel {
  // Atributos:
  // Valores de conversão:
  double _usd;
  double _eur;
  double _btc;

  // Lista de moedas válidas;
  static List<String> moedas = ['USD', 'EUR', 'BTC'];

  MoedaModel._fromJson(Map<String, dynamic> json) {
    _usd = json['USD'];
    _eur = json['EUR'];
    _btc = json['BTC'];
  }

  static Future<MoedaModel> _consulta() async {
    var url = Uri.parse('https://api.senac.estevaorada.com/api/moeda/BRL');
    // Chamada assíncrona:
    var resposta = await get(url);
    var json = jsonDecode(resposta.body);
    // retornar o objeto pelo factory:
    return MoedaModel._fromJson(json);
  }

  static Future<double> converter(String moeda, double valor) async {
    MoedaModel m = await MoedaModel._consulta();
    if (moeda == 'USD') {
      return valor / m._usd;
    } else if (moeda == 'EUR') {
      return valor / m._eur;
    } else if (moeda == 'BTC') {
      return valor / m._btc;
    } else {
      return 0.0;
    }
  }
}

///////////////////////////////////////////////////////////////////////////////////////
// CONTROLLER:
Future<String> calcular() async {
    var r = await MoedaModel.converter(itemSelecionado, valor);
    return r.toStringAsFixed(2);
  }

///////////////////////////////////////////////////////////////////////////////////////
// VIEW:

import 'package:conversor_imc_flutter/src/controller/conversormoeda_controller.dart';
import 'package:conversor_imc_flutter/src/models/moeda_model.dart';
import 'package:conversor_imc_flutter/src/views/components/drawer.dart';
import 'package:conversor_imc_flutter/src/views/components/espacamento_h.dart';
import 'package:conversor_imc_flutter/src/views/components/espacamento_w.dart';
import 'package:conversor_imc_flutter/src/views/components/titulo2.dart';
import 'package:flutter/material.dart';

class ConversorMoeda extends StatefulWidget {
  @override
  _ConversorMoedaState createState() => _ConversorMoedaState();
}

class _ConversorMoedaState extends State<ConversorMoeda> {
  ConversorMoedaController controller = ConversorMoedaController();
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      //drawer: DrawerInicio(),
      appBar: AppBar(
        title: Text('Conversor de Moeda'),
      ),
      body: Container(
        width: double.infinity,
        height: double.infinity,
        child: SingleChildScrollView(
          child: Padding(
            padding: const EdgeInsets.all(15.0),
            child: Column(
              children: [
                EspacamentoH(h: 20),
                Image.asset(
                  'assets/images/icon_conversor.png',
                  width: 200,
                  height: 200,
                ),
                // Container de espaçamento:
                EspacamentoH(h: 20),
                Titulo2(txt: "Conversor de Moeda:"),
                // Campo de entrada de moeda:
                TextField(
                  keyboardType: TextInputType.number,
                  decoration: InputDecoration(
                    labelText: 'Valor em R\$',
                  ),
                  onChanged: (value) async {
                    controller.valor = double.tryParse(value) ?? 0.0;
                  },
                ),
                // Linha com os campos de resultado:
                Row(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    // Dropdown:
                    Expanded(
                        flex: 1,
                        child: SizedBox(
                          height: 56,
                          // Item do dropdown:
                          child: DropdownButton(
                            onChanged: (value) {
                              setState(() {
                                controller.itemSelecionado = value;
                              });
                            },
                            isExpanded: true,
                            value: controller.itemSelecionado,
                            iconEnabledColor: Colors.pink,
                            underline: Container(
                              height: 1,
                              color: Colors.pink,
                            ),
                            items: controller.moedas.map((valor) {
                              return DropdownMenuItem(
                                  child: Text(valor), value: valor);
                            }).toList(),
                          ),
                        )),
                    // Container de espaçamento:
                    EspacamentoW(w: 10),
                    // TextField
                    Expanded(
                      flex: 2,
                      child: TextField(
                        controller: controller.campoResultado,
                        enabled: false,
                        decoration: InputDecoration(),
                      ),
                    ),
                  ],
                ),
                ElevatedButton(
                    onPressed: () async {
                      controller.campoResultado.text =
                          await controller.calcular();
                      setState(() {});
                    },
                    child: Text("CONVERTER")),
                Text(controller.campoResultado.text)
              ],
            ),
          ),
        ),
      ),
    );
  }
}