Flutter & Firebase プロジェクト作成からエミュレータ環境構築まで（FlutterFireを用いた方法）

dart pub global activate flutterfire_cli

dart pub global list

Installed executable flutterfire.
Warning: Pub installs executables into $HOME/.pub-cache/bin, which is not on your path.
You can fix that by adding this to your shell's config file (.bashrc, .bash_profile, etc.):

  export PATH="$PATH":"$HOME/.pub-cache/bin"

flutter create -i swift -a kotlin my_flutter_app

flutter run

flutterfire configure

# パスを通していない場合は以下で実行
# ~/.pub-cache/bin/flutterfire configure

i Found 3 Firebase projects.
? Select a Firebase project to configure your Flutter application with ›
❯ my-first-sample-project (my-first-sample-project)
  my-second-sample-project (my-second-sample-project)
  my-third-sample-project (my-third-sample-project)
  <create a new project>

i Found 3 Firebase projects.
✔ Select a Firebase project to configure your Flutter application with · <create a new project>

✔ Enter a project id for your new Firebase project (e.g. my-cool-project) · my-super-cool-flutter-project
i New Firebase project my-super-cool-flutter-project created succesfully.

? Which platforms should your configuration support (use arrow keys & space to select)? ›
✔ android
✔ ios
  macos
✔ web

✔ Which ios bundle id do you want to use for this configuration, e.g. 'com.example.app'? · com.example.app
i Registered a new Firebase ios app on Firebase project my-super-cool-flutter-project.
i Registered a new Firebase web app on Firebase project my-super-cool-flutter-project.

Firebase configuration file lib/firebase_options.dart generated successfully with the following Firebase apps:
Platform  Firebase App Id
web       1:************:web:0123456789abcdefghijkl
android   1:************:android:0123456789abcdefghijkl
ios       1:************:ios:0123456789abcdefghijkl

// File generated by FlutterFire CLI.
// ignore_for_file: lines_longer_than_80_chars
import 'package:firebase_core/firebase_core.dart' show FirebaseOptions;
import 'package:flutter/foundation.dart'
    show defaultTargetPlatform, kIsWeb, TargetPlatform;

/// Default [FirebaseOptions] for use with your Firebase apps.
///
/// Example:
/// ```dart
/// import 'firebase_options.dart';
/// // ...
/// await Firebase.initializeApp(
///   options: DefaultFirebaseOptions.currentPlatform,
/// );
/// ```
class DefaultFirebaseOptions {
  static FirebaseOptions get currentPlatform {
    if (kIsWeb) {
      return web;
    }
    // ignore: missing_enum_constant_in_switch
    switch (defaultTargetPlatform) {
      case TargetPlatform.android:
        return android;
      case TargetPlatform.iOS:
        return ios;
      case TargetPlatform.macOS:
        throw UnsupportedError(
          'DefaultFirebaseOptions have not been configured for macos - '
          'you can reconfigure this by running the FlutterFire CLI again.',
        );
    }

    throw UnsupportedError(
      'DefaultFirebaseOptions are not supported for this platform.',
    );
  }

  static const FirebaseOptions web = FirebaseOptions(
    // ...
  );

  static const FirebaseOptions android = FirebaseOptions(
    // ...
  );

  static const FirebaseOptions ios = FirebaseOptions(
    // ...
  );
}

flutter pub add firebase_core

dependencies:
  flutter:
    sdk: flutter
  firebase_core: ^1.0.0

// import を追加
import 'package:firebase_core/firebase_core.dart';
import 'firebase_options.dart';

// main() を編集
void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp(
    options: DefaultFirebaseOptions.currentPlatform,
  );
  runApp(const MyApp());
}

flutter pub add firebase_database

dependencies:
  flutter:
    sdk: flutter
  firebase_core: ^1.0.0
  firebase_database: ^9.0.0

Launching lib/main.dart on iPhone 13 in debug mode...

（省略）

Specs satisfying the `firebase_database (from `.symlinks/plugins/firebase_database/ios`)` dependency were found, but they required a higher minimum deployment target.

（省略）

[!] Automatically assigning platform `iOS` with version `9.0` on target `Runner` because no platform was specified. Please specify a platform for this target in your Podfile.

# [更新前]
# platform :ios, '9.0'

# [更新後]
platform :ios, '10.0'

┌─ Flutter Fix ──────────────────────────────────────────────────────────────────────────────────────────────┐
│ The plugin firebase_database requires a higher Android SDK version.                                        │
│ Fix this issue by adding the following to the file android/app/build.gradle:                               │
│ android {                                                                                                  │
│   defaultConfig {                                                                                          │
│     minSdkVersion 19                                                                                       │
│   }                                                                                                        │
│ }                                                                                                          │
│                                                                                                            │
│                                                                                                            │
│ Note that your app won't be available to users running Android SDKs below 19.                              │
│ Alternatively, try to find a version of this plugin that supports these lower versions of the Android SDK. │
└────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

// [更新前]
android {
    defaultConfig {
        minSdkVersion flutter.minSdkVersion
    }
}

// [更新前]
android {
    defaultConfig {
        minSdkVersion 21
    }
}

// import を追加
import 'package:firebase_database/firebase_database.dart';

// _incrementCounter() を編集
void _incrementCounter() {
  FirebaseDatabase database = FirebaseDatabase.instance;
  DatabaseReference ref = database.ref().child('count');

  _counter++;

  ref.set(_counter);

  setState(() {
    _counter;
  });
}