「flutter」データの渡し方について。

やりたいこと

flutterの練習で天気を取得するアプリを作っているのですが、「_select = _kenmei[index];」で受けた値を「 String cityId = '大阪府';」へ再代入したいのですが、うまく渡すことができませんでした。

ご教授お願いいたします。

該当のコード

new.dart
1import 'package:flutter/cupertino.dart';
2import 'package:flutter/material.dart';
3
4class NewLocal extends StatefulWidget {
5  @override
6  _NewLocalState createState() => _NewLocalState();
7}
8
9class _NewLocalState extends State<NewLocal> {
10  String _select = "none";
11
12  final List<String> _kenmei = [
13    '北海道',
14    '青森県',
15    '秋田県',
16    '岩手県',
17    '宮城県',
18    '福島県',
19    '茨城県',
20    '栃木県',
21    '群馬県',
22    '埼玉県',
23    '千葉県',
24    '神奈川県',
25  ];
26
27  @override
28  Widget build(BuildContext context ) {
29
30    return CupertinoPicker(
31      scrollController: FixedExtentScrollController(
32        initialItem: 9,
33      ),
34      itemExtent: 47,
35      children: _kenmei.map((String item) => Text(item)).toList(),
36      onSelectedItemChanged: newLocal,
37    );
38  }
39
40  String newLocal(int index) {
41    setState(() {
42      _select = _kenmei[index];
43      print(_select);
44    });
45  }
46}

main.dart
1import 'package:flutter/material.dart';
2import 'dart:async';
3import 'dart:convert';
4import 'package:http/http.dart' as http;
5import 'package:weather_app/main_widget.dart';
6
7Future<WeatherInfo> fetchWeather () async{
8
9
10  WeatherInfo weatherInfo = WeatherInfo();
11
12  String cityId = '大阪府';
13  final apiKey = 'xxxxxxxxxxxxxxxxx';
14  final requestUrl = 'http://api.openweathermap.org/data/2.5/weather?q=${cityId}&lang=ja&units=metric&appid=${apiKey}';
15
16  final response = await http.get(Uri.parse(requestUrl));
17
18  if(response.statusCode == 200){
19    return WeatherInfo.fromJson(jsonDecode(response.body));
20  }else{
21    throw Expanded(child: Center(child: Text('読み込みエラー'),
22    ),
23    );
24  }
25}
26
27class WeatherInfo {
28  final String location;
29  final double temp;
30  final double tempMin;
31  final double tempMax;
32  final String weather;
33  final int humidity;
34  final double windSpeed;
35
36  WeatherInfo({
37    @required this.location,
38    @required this.temp,
39    @required this.tempMin,
40    @required this.tempMax,
41    @required this.weather,
42    @required this.humidity,
43    @required this.windSpeed,
44  });
45
46  factory WeatherInfo.fromJson(Map<String, dynamic> json){
47    return WeatherInfo(
48        location: json['name'],
49        temp: json['main']['temp'],
50        tempMin: json['main']['temp_min'],
51        tempMax: json['main']['temp_max'],
52        weather: json['weather'][0]['description'],
53        humidity: json['main']['humidity'],
54        windSpeed: json['wind']['speed']
55    );
56  }
57}
58
59
60void  main () => runApp(
61    MaterialApp(
62        title: "お天気アプリ",
63        home:MyApp()
64    )
65);
66
67class MyApp extends StatefulWidget {
68  @override
69  _MyAppState createState() => _MyAppState();
70}
71
72class _MyAppState extends State<MyApp> {
73
74  Future<WeatherInfo> futureWeather;
75
76  @override
77  void initState(){
78    super.initState();
79    futureWeather = fetchWeather();
80  }
81
82  @override
83  Widget build(BuildContext context) {
84    return Scaffold(
85        body: FutureBuilder<WeatherInfo>(
86          future: futureWeather,
87          builder: (context, snapshot){
88            if(snapshot.hasData){
89              return MainWidget(
90                location: snapshot.data.location,
91                temp: snapshot.data.temp,
92                tempMin: snapshot.data.tempMin,
93                tempMax: snapshot.data.tempMax,
94                weather: snapshot.data.weather,
95                humidity: snapshot.data.humidity,
96                windSpeed: snapshot.data.windSpeed,
97              );
98            }else if(snapshot.hasError){
99              return Center(
100                child: Text('スナップショットのエラー'),
101              );
102            }
103            return CircularProgressIndicator();
104          },
105        )
106    );
107  }
108}