【Flutter】pigeonについての公式の記載の整理と公式サンプルを使用し実機で確認

dev_dependencies:
  flutter_test:
    sdk: flutter
  flutter_lints: ^5.0.0
  pigeon: ^25.5.0

import 'package:pigeon/pigeon.dart';

@ConfigurePigeon(
  PigeonOptions(
	  dartOut: 'lib/src/messages.g.dart',
    dartOptions: DartOptions(),
    kotlinOut: 'android/app/src/main/kotlin/dev/flutter/pigeon_example_app/Messages.g.kt',
    kotlinOptions: KotlinOptions(),
    swiftOut: 'ios/Runner/Messages.g.swift',
    swiftOptions: SwiftOptions(),
    dartPackageName: 'pigeon_example_package',
  ),
)

dart run pigeon --input path/to/input.dart

enum Code { one, two }

class MessageData {
  MessageData({required this.code, required this.data});
  String? name;
  String? description;
  Code code;
  Map<String, String> data;
}

@HostApi()
abstract class ExampleHostApi {
  String getHostLanguage();

　// 非同期処理を想定するため@asyncを定義
  @async
  bool sendMessage(MessageData message);
}

final ExampleHostApi _api = ExampleHostApi();

/// MessageDataクラス, HostApiを使用してメッセージを送信
Future<bool> sendMessage(String messageText) {
  final MessageData message = MessageData(
    code: Code.one,
    data: <String, String>{'header': 'this is a header'},
    description: 'uri text',
  );
  try {
    return _api.sendMessage(message);
  } catch (e) {
    // エラーハンドリング
    return Future<bool>(() => true);
  }
}

private class PigeonApiImplementation: ExampleHostApi {
  func getHostLanguage() throws -> String {
    return "Swift"
  }

  func sendMessage(message: MessageData, completion: @escaping (Result<Bool, Error>) -> Void) {
    if message.code == Code.one {
      completion(.failure(PigeonError(code: "code", message: "message", details: "details")))
      return
    }
    completion(.success(true))
  }
}

let controller: FlutterViewController = window?.rootViewController as! FlutterViewController
// ✅ Pigeon API の登録
ExampleHostApiSetup.setUp(binaryMessenger: controller.binaryMessenger, api: PigeonApiImplementation())

  final MessageData message = MessageData(
    code: Code.one,
    data: <String, String>{'header': 'this is a header'},
    description: 'uri text',
  );

            ElevatedButton(
                onPressed: () async {
                  try {
                    final value = await sendMessage('Test');
                    print('Message sent successfully: $value');
                  } catch (error) {
                    print('Error sending message: $error');
                  }
                },
                child: Text('Button')),

            ElevatedButton(
                onPressed: () async {
                  final hostLanguage = await getHostLanguage();
                  print('Host language: $hostLanguage');
                },
                child: Text('Button 2')),

@FlutterApi()
abstract class MessageFlutterApi {
  String flutterMethod(String? aString);
}

/// ExampleFlutterApiの実装
class _ExampleFlutterApi implements MessageFlutterApi {
  @override
  String flutterMethod(String? aString) {
    // Flutter側の処理を実装
    return aString ?? 'test';
  }
}

/// ExampleFlutterApiのセットアップ
void setupExampleFlutterApi() {
  MessageFlutterApi.setUp(_ExampleFlutterApi());
} 

private class PigeonFlutterApi {
  var flutterAPI: MessageFlutterApi

  init(binaryMessenger: FlutterBinaryMessenger) {
    flutterAPI = MessageFlutterApi(binaryMessenger: binaryMessenger)
  }

  func callFlutterMethod(
    aString aStringArg: String?, completion: @escaping (Result<String, PigeonError>) -> Void
  ) {
    flutterAPI.flutterMethod(aString: aStringArg) {
      completion($0)
    }
  }
}

    var pigeonFlutterApi: PigeonFlutterApi?
    
    
        override func application(
        _ application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
    ) -> Bool {
        let controller: FlutterViewController = window?.rootViewController as! FlutterViewController
            // Flutter API の登録
        pigeonFlutterApi = PigeonFlutterApi(binaryMessenger: controller.binaryMessenger)
        
        // ネイティブ画面（ダミー ViewController）をすぐ表示してテスト
        DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
          let nativeVC = NativeViewController()
          nativeVC.pigeonFlutterApi = self.pigeonFlutterApi
          controller.present(nativeVC, animated: true, completion: nil)
        }
        
        
        return super.application(application, didFinishLaunchingWithOptions: launchOptions)
    }

import UIKit

class NativeViewController: UIViewController {
  var pigeonFlutterApi: PigeonFlutterApi?

  override func viewDidLoad() {
    super.viewDidLoad()
      view.backgroundColor = .white

    let closeButton = UIButton(type: .system)
    closeButton.setTitle("Close & Notify Flutter", for: .normal)
    closeButton.addTarget(self, action: #selector(closeButtonTapped), for: .touchUpInside)
    closeButton.frame = CGRect(x: 50, y: 200, width: 220, height: 44)
    view.addSubview(closeButton)
  }

  @objc func closeButtonTapped() {
    pigeonFlutterApi?.callFlutterMethod(aString: "Native screen closed") { result in
      switch result {
      case .success(let response):
        print("Flutter returned: \\(response)")
      case .failure(let error):
        print("Error: \\(error)")
      }
    }

    // 閉じる処理（画面を閉じたい場合）
    dismiss(animated: true, completion: nil)
  }
}

Flutter returned: Native screen closed