main.dart cryptoapp

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

final String apiUrl = 'https://api.coinmarketcap.com/v1/ticker/?convert=IDR&limit=20';

@override
Future<List> fetchCurrencies() async {
    http.Response response = await http.get(apiUrl);
    String responseBody = response.body;
    final statusCode = response.statusCode;

    if (statusCode < 200 || statusCode >= 300 || responseBody == Null) {
      throw new FetchDataException('An error occured : [Status Code : $statusCode]');
    }

    final List cryptoItems = json.decode(responseBody);
    return cryptoItems;
}

class FetchDataException implements Exception {
  final _message;

  FetchDataException([this._message]);

  String toString() {
    if (_message == null) return "Exception";
    return "Exception: $_message";
  }
}

void main() async {
  List currencies = await fetchCurrencies();

  runApp(
    new MaterialApp(
      title: 'Flutter Demo',
      theme: new ThemeData(
        primarySwatch: Colors.purple,
      ),
      home: new CryptoHome(currencies),
    )
  );
}

class CryptoHome extends StatelessWidget {

  final List _currencies;
  final List<MaterialColor> _colors = [Colors.blue, Colors.indigo, Colors.red];

  CryptoHome(this._currencies);

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      body: _buildBody(),
      backgroundColor: Colors.purple,
    );
  }

  Widget _buildBody() {
    return new Container(
      margin: const EdgeInsets.fromLTRB(8.0, 56.0, 8.0, 0.0),
      child: new Column(
        children: <Widget>[
          _getAppTitleWidget(),
          _getListViewWidget()
        ],
      ),
    );
  }

  Widget _getAppTitleWidget() {
    return new Container(
      margin: const EdgeInsets.only(bottom: 16.0),
      child: new Center(
        child: new Text(
        'Cryptocurrencies',
        style: new TextStyle(
          color: Colors.white,
          fontWeight: FontWeight.bold,
          fontSize: 24.0
          ),
        )
      )
    );
  }

  Widget _getListViewWidget() {
    return new Flexible(
      child: new ListView.builder(
        itemCount: _currencies.length,
        itemBuilder: (context, index) {
          final Map currency = _currencies[index];
          final MaterialColor color = _colors[index % _colors.length];

          return _getListItemWidget(currency, color);
        },
      ),
    );
  }

  Container _getListItemWidget(Map currency, MaterialColor color) {
    return new Container(
      margin: const EdgeInsets.only(top: 5.0),
      child: new Card(
        child: _getListTileWidget(currency, color),
      ),
    );
  }

  ListTile _getListTileWidget(Map currency, MaterialColor color) {
    return new ListTile(
      leading: _getLeadingWidget(currency['name'], color),
      title: _getTitleWidget(currency['name']),
      subtitle: _getSubtitleWidget(currency['price_usd'], currency['percent_change_1h']),
      isThreeLine: true,
    );
  }

  CircleAvatar _getLeadingWidget(String currencyName, MaterialColor color) {
    return new CircleAvatar(
      backgroundColor: color,
      child: new Text(currencyName[0]),
    );
  }

  Text _getTitleWidget(String currencyName) {
    return new Text(
      currencyName,
      style: new TextStyle(
        fontWeight: FontWeight.bold
      ),
    );
  }

  Text _getSubtitleWidget(String priceUsd, String percentChange1h) {
    return new Text(
      '\$$priceUsd\n1 hour: $percentChange1h'
    );
  }
}