How to communicate between Flutter and the host platform (Android/iOS) using pigeon

A simple demonstration of pigeon library. Pigeon is a code generator tool to make communication between Flutter and the host platform type-safe, easier, and faster.

Steps

• Add pigeon as a dev_dependency.

  dev_dependencies:
      pigeon: ^15.0.2
  

• Make a .dart file outside of your lib directory for defining the communication interface.

  • create a separate directory(outside lib) say pigeons and create a dart data file(tweet.dart) as below.

    import 'package:pigeon/pigeon.dart';
    
    class Tweet {
        Tweet({
                required this.id,
                required this.message,
                required this.dateTime,
                required this.userId,
            });
            
            final int id;
            final String message;
            final int dateTime;
            final int userId;
    }
    
    @HostApi()
    abstract class TweetApi {
        Tweet getTweet();
    }

• Run pigeon on your .dart file to generate the required Dart and host-language code: flutter pub get then flutter pub run pigeon with suitable arguments.

  • it will generate Tweet.g.dart, Tweet.g.kt and Tweet.g.swift for respective platform Flutter, Android, and iOS.

• Add the generated Dart code to ./lib for compilation. ie tweet.g.dart

• Implement the host-language code and add it to your build

Android

    import io.flutter.embedding.android.FlutterActivity
    import io.flutter.embedding.engine.FlutterEngine
    import java.time.Instant

    class MainActivity: FlutterActivity(), TweetApi {

        override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
            val binaryMessenger = flutterEngine.dartExecutor.binaryMessenger
            TweetApi.setUp(binaryMessenger, this)
        }

        override fun getTweet(): Tweet {
            return Tweet(
                id = 1,
                message = "Tweet from Android",
                dateTime = Instant.now().toEpochMilli(),
                userId = 1001
            )
        }
    }

iOS

    import UIKit
    import Flutter

    @UIApplicationMain
    @objc class AppDelegate: FlutterAppDelegate, TweetApi {
        override func application(
            _ application: UIApplication,
            didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
        ) -> Bool {
            GeneratedPluginRegistrant.register(with: self)
            
            let rootViewController : FlutterViewController = window?.rootViewController as! FlutterViewController

            // get binaryMessenger
            let binaryMessenger = rootViewController as! FlutterBinaryMessenger
            TweetApiSetup.setUp(binaryMessenger: binaryMessenger, api: self)
            
            return super.application(application, didFinishLaunchingWithOptions: launchOptions)
        }
        
        func getTweet() throws -> Tweet {
            let date = Date()
            let milliseconds = Int64(date.timeIntervalSince1970 * 1000)
            return Tweet(id: 1, message: "Tweet from iOS", dateTime: milliseconds, userId: 1001)
        }
    }

• Call the generated Dart methods from your widget.

  final tweetApi = TweetApi();
  final tweet = await tweetApi.getTweet();

complete sourcecode