flutter with firebase

https://qiita.com/kimuradesu/items/b74c4908efb282d16a46 ::blazor with firebase

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://www.flutter-study.dev/　フラッターではじめるアプリ開発（ベータ版でWebもOK）

https://airhole.ymegane.org/flutter-for-web/  いまさらでもないが

ちなみに工学社の本は参考程度　上記のサイトのほうがまし

ツヤノの本は、firebase記事はないが、それ以外は充実 (とくにカメラ利用）

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いろいろあたってなんとか動いた記録

まず最新のflutter_core,cloud_firestoreをpub.get 

----------------------------------------------------------------      pubspec.yaml

name: my_flutter_app
description: A new Flutter application.

# The following line prevents the package from being accidentally published to
# pub.dev using `pub publish`. This is preferred for private packages.
publish_to: 'none' # Remove this line if you wish to publish to pub.dev

# The following defines the version and build number for your application.
# A version number is three numbers separated by dots, like 1.2.43
# followed by an optional build number separated by a +.
# Both the version and the builder number may be overridden in flutter
# build by specifying --build-name and --build-number, respectively.
# In Android, build-name is used as versionName while build-number used as versionCode.
# Read more about Android versioning at https://developer.android.com/studio/publish/versioning
# In iOS, build-name is used as CFBundleShortVersionString while build-number used as CFBundleVersion.
# Read more about iOS versioning at
# https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
version: 1.0.0+1

environment:
  sdk: ">=2.7.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter


  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^1.0.0
  firebase_core: "^0.7.0"
  cloud_firestore: "^0.16.0"

dev_dependencies:
  flutter_test:
    sdk: flutter

# For information on the generic Dart part of this file, see the
# following page: https://dart.dev/tools/pub/pubspec

# The following section is specific to Flutter.
flutter:

  # The following line ensures that the Material Icons font is
  # included with your application, so that you can use the icons in
  # the material Icons class.
  uses-material-design: true

  # To add assets to your application, add an assets section, like this:
  # assets:
  #   - images/a_dot_burr.jpeg
  #   - images/a_dot_ham.jpeg

  # An image asset can refer to one or more resolution-specific "variants", see
  # https://flutter.dev/assets-and-images/#resolution-aware.

  # For details regarding adding assets from package dependencies, see
  # https://flutter.dev/assets-and-images/#from-packages

  # To add custom fonts to your application, add a fonts section here,
  # in this "flutter" section. Each entry in this list should have a
  # "family" key with the font family name, and a "fonts" key with a
  # list giving the asset and other descriptors for the font. For
  # example:
  # fonts:
  #   - family: Schyler
  #     fonts:
  #       - asset: fonts/Schyler-Regular.ttf
  #       - asset: fonts/Schyler-Italic.ttf
  #         style: italic
  #   - family: Trajan Pro
  #     fonts:
  #       - asset: fonts/TrajanPro.ttf
  #       - asset: fonts/TrajanPro_Bold.ttf
  #         weight: 700
  #
  # For details regarding fonts from package dependencies,
  # see https://flutter.dev/custom-fonts/#from-packages

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android-package-name for firebase is com.example.my_flutter_app

(my_flutter_appというflutter project nameから導出される）　

できたjsonをmy_flutter_app/android/appに転送

firestoreにbooksというコレクションを作りauthor,titleの項目をつくり入れ込んでおく

----------------------------------------------------- main.dart

import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:firebase_core/firebase_core.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyHomePage());
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  var count = 1;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Firestore Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        appBar: AppBar(
          title: Text('Flutter Firestore Demo'),
        ),
        body: createListView(),
        floatingActionButton: FloatingActionButton(
          onPressed: () {
            // Firestore 上にデータを追加
            //
            FirebaseFirestore.instance.collection('books').add({
              'title': 'タイトル$count',
              'author': '著者$count',
            });
            count += 1;
          },
          child: Icon(Icons.add),
        ),
      ),
    );
  }

  createListView() {
    FirebaseFirestore.instance.collection('books').snapshots().listen((data) {
      print(data);
    });

    return StreamBuilder(
      stream: FirebaseFirestore.instance.collection('books').snapshots(),
      builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
        // エラーの場合
        if (snapshot.hasError) {
          return Text('Error: ${snapshot.error}');
        }

        // 通信中の場合
        switch (snapshot.connectionState) {
          case ConnectionState.waiting:
            return Text('Loading ...');
          default:
            return ListView(
              children: snapshot.data.docs.map((DocumentSnapshot document) {
                return new ListTile(
                  title: new Text(document['title']),
                  subtitle: new Text(document['author']),
                );
              }).toList(),
            );
        }
      },
    );
  }
}

----------------------------------------------------------navigation ex

import 'package:flutter/material.dart';

void main() =>
  runApp(MaterialApp(
    initialRoute: '/first',
    routes: <String, WidgetBuilder> {
'/first':(BuildContext context) => FirstRoute(),
'/second': (BuildContext context) => SecondRoute(),
}
));

class FirstRoute extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('First Route'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            RaisedButton(
              onPressed: () {
                Navigator.push(context,
                MaterialPageRoute(
                  builder: (context) => SecondRoute()
                ));
              },
              child: Text('push here',
              style: TextStyle(fontSize: 20),
            )),
    ],),),);
  }
}

class SecondRoute extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Second Route'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            RaisedButton(
                onPressed: () {
                  Navigator.pop(context);
                },
                child: Text('push here',
                  style: TextStyle(fontSize: 20),
                )),
          ],),),);
  }
}