Simple local restaurant query app

main.dart

import 'dart:async';
import 'package:flutter/material.dart';
import './places.dart';

const lat = 37.7576792;
const long = -122.5078112;

void main() => runApp(new MyApp());

class MyApp extends StatelessWidget {
  static List<Place> _favPlaces = <Place>[];  // ignore, it's for the next feature
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
        title: 'Polymer Demo',
        theme: new ThemeData(
          primarySwatch: Colors.red,
        ),
        home: new Scaffold(
            appBar: new AppBar(
              title: new Text('Home'),
            ),
            body: new HomeScreen()));
  }
}

class HomeScreen extends StatefulWidget {
  HomeScreen({Key key, this.title}) : super(key: key);
  final String title;

  @override
  _HomeScreenState createState() => new _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  List<Place> _places = <Place>[];

  @override
  initState() {
    super.initState();
    listenForPlaces();
  }

  void listenForPlaces() async {
    var stream = await getPlaces(lat, long);
    stream.listen((place) =>
        // _places.add(place);
        setState(() => _places.add(place)));
  }

  @override
  Widget build(BuildContext context) {
    return new ListView(
      children: _places.map((place) => new PlaceWidget(place)).toList(),
    );
  }
}

class PlaceWidget extends StatefulWidget {
  @override
  _PlaceWidgetState createState() {
    return new _PlaceWidgetState(place, false);
  }

  final Place place;
  PlaceWidget(this.place, {Key key}) : super(key: key);
}

class _PlaceWidgetState extends State<PlaceWidget> {
  final Place _place;
  bool favorited;

  _PlaceWidgetState(this._place, this.favorited);

  @override
  Widget build(BuildContext context) {
    return new ListTile(
      key: new PageStorageKey(_PlaceWidgetState),
      title: new Text(_place.name),
      subtitle:
          new Text(_place.address, style: Theme.of(context).textTheme.caption),
      leading: new CircleAvatar(
        child: new Text(_place.rating.toString()),
        backgroundColor:
            favorited ? Colors.green : Theme.of(context).primaryColor,
      ),
      trailing: new GestureDetector(
        onTap: () {
          final snackBar =
              new SnackBar(content: new Text("Tapped on " + _place.name));
          Scaffold.of(context).showSnackBar(snackBar);
          setState(() {
            favorited = !favorited;
          });
          MyApp._favPlaces.add(_place);
          print(MyApp._favPlaces);
        },
        child: favorited
            ? new Icon(Icons.favorite, color: Colors.red)
            : new Icon(Icons.favorite_border),
      ),
    );
  }
}

class SecondScreen extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return new Scaffold(
        appBar: new AppBar(title: new Text('Supplementary Screen')),
        body: new Center(
            child: new RaisedButton(
          child: new Text('go back to screen 1'),
          onPressed: () {
            Navigator.pop(context);
          },
        )));
  }
}

places.dart

// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

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

import '../key.dart' show key;


main() {
  getPlaces(37.7576792, -122.5078112);
}

class Place {
  final String name;
  final double rating;
  final String address;

  Place.fromJson(Map jsonMap) :
    name = jsonMap['name'],
    rating = jsonMap['rating']?.toDouble() ?? -1.0,
    address = jsonMap['vicinity'];

  String toString() => 'Place: $name';
}

Future<Stream<Place>> getPlaces(double lat, double lng) async {
  var url = 'https://maps.googleapis.com/maps/api/place/nearbysearch/json' +
    '?location=$lat,$lng' +
    '&radius=1000&type=restaurant' +
    '&key=$key';

  // http.get(url).then(
  //   (res) => print(res.body)
  // );
  
  var client = new http.Client();
  var streamedRes = await client.send(new http.Request('get', Uri.parse(url)));

  return streamedRes.stream
    .transform(UTF8.decoder)
    .transform(JSON.decoder)
    .expand((jsonBody) => (jsonBody as Map)['results'] )
    .map((jsonPlace) => new Place.fromJson(jsonPlace));
}