Flutter自动生成代码插件auto_pigeon的使用

当然，以下是如何在Flutter项目中使用auto_pigeon插件自动生成代码的一个示例。auto_pigeon主要用于在Flutter和原生平台代码（如Dart与Kotlin/Swift）之间生成通信代码，从而减少手动编写平台通道代码的工作量。

步骤 1: 添加依赖

首先，在你的pubspec.yaml文件中添加auto_pigeon的依赖：

dependencies:
  flutter:
    sdk: flutter

dev_dependencies:
  auto_pigeon: ^0.x.y  # 请使用最新版本号
  build_runner: ^2.0.0

注意：将0.x.y替换为auto_pigeon的最新版本号。

步骤 2: 定义接口

创建一个Dart文件，例如messaging.dart，在其中定义你希望跨平台通信的接口。

// messaging.dart
import 'package:auto_pigeon/auto_pigeon.dart';

@HostApi()
abstract class MessagingApi {
  void sendMessage(String message);
  Future<String> getMessage();
}

步骤 3: 生成代码

在项目的根目录下运行以下命令来生成代码：

flutter pub run build_runner build

这将生成两个文件：messaging_api.dart（Dart端）和对应的平台端代码（如MessagingApi.kt或MessagingApi.swift）。

步骤 4: 实现平台端代码

iOS (Swift)

在ios/Runner/GeneratedPluginRegistrant.swift中确保注册了生成的代码（通常自动完成）。然后在MessagingApi.swift中实现接口：

// MessagingApi.swift (自动生成的文件)
import Foundation
import Flutter

class MessagingApiImpl: NSObject, FlutterPlugin, MessagingApiProtocol {
    public static func register(with registrar: FlutterRegistrar) {
        let channel = FlutterMethodChannel(name: "plugins.flutter.io/messaging_api", binaryMessenger: registrar.messenger())
        let instance = MessagingApiImpl()
        registrar.addMethodCallDelegate(instance, channel: channel)
        _ = MessagingApi(channel: channel, messenger: registrar.messenger())
    }
    
    private let channel: FlutterMethodChannel
    
    required init(channel: FlutterMethodChannel, messenger: FlutterBinaryMessenger) {
        self.channel = channel
        super.init()
        channel.setMethodCallHandler({ [weak self] call, result in
            guard let self = self else {
                result(.failed("Plugin deallocated"))
                return
            }
            switch call.method {
            case "sendMessage":
                if let message = call.arguments as? String {
                    self.sendMessage(message: message)
                } else {
                    result(.failed("Invalid argument type"))
                }
            case "getMessage":
                self.getMessage(result: result)
            default:
                result(.notImplemented)
            }
        })
    }
    
    func sendMessage(message: String) {
        // 实现发送消息的逻辑
        print("Message sent: \(message)")
    }
    
    func getMessage(result: @escaping FlutterResult) {
        // 实现获取消息的逻辑
        let message = "Hello from iOS"
        result(message)
    }
}

Android (Kotlin)

在android/app/src/main/kotlin/.../MainActivity.kt中确保注册了生成的代码（通常自动完成）。然后在MessagingApi.kt中实现接口：

// MessagingApi.kt (自动生成的文件)
package io.flutter.plugins.generated

import io.flutter.embedding.engine.plugins.FlutterPlugin
import io.flutter.embedding.engine.plugins.activity.ActivityAware
import io.flutter.embedding.engine.plugins.activity.ActivityPluginBinding
import io.flutter.plugin.common.MethodCall
import io.flutter.plugin.common.MethodChannel
import io.flutter.plugin.common.MethodChannel.MethodCallHandler
import io.flutter.plugin.common.MethodChannel.Result
import androidx.annotation.NonNull

class MessagingApiImpl : MethodCallHandler, FlutterPlugin, ActivityAware {
    private lateinit var channel: MethodChannel

    override fun onAttachedToEngine(@NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
        channel = MethodChannel(flutterPluginBinding.binaryMessenger, "plugins.flutter.io/messaging_api")
        channel.setMethodCallHandler(this)
    }

    override fun onMethodCall(@NonNull call: MethodCall, @NonNull result: Result) {
        when (call.method) {
            "sendMessage" -> {
                val message = call.argument<String>("message") ?: run {
                    result.error("INVALID_ARGUMENT", "Message argument is missing", null)
                    return
                }
                sendMessage(message)
                result.success(null)
            }
            "getMessage" -> {
                val message = getMessage()
                result.success(message)
            }
            else -> result.notImplemented()
        }
    }

    override fun onDetachedFromEngine(@NonNull binding: FlutterPlugin.FlutterPluginBinding) {
        channel.setMethodCallHandler(null)
    }

    private fun sendMessage(message: String) {
        // 实现发送消息的逻辑
        println("Message sent: $message")
    }

    private fun getMessage(): String {
        // 实现获取消息的逻辑
        return "Hello from Android"
    }

    // ActivityAware interface methods (if needed)
    override fun onAttachedToActivity(binding: ActivityPluginBinding) {}
    override fun onDetachedFromActivityForConfigChanges() {}
    override fun onReattachedToActivityForConfigChanges(binding: ActivityPluginBinding) {}
    override fun onDetachedFromActivity() {}
}

步骤 5: 在Flutter中使用生成的API

最后，在你的Flutter代码中，你可以使用生成的API来与原生代码通信：

// main.dart
import 'package:flutter/material.dart';
import 'messaging_api.dart'; // 自动生成的文件

void main() {
  runApp(MyApp());
}

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  late MessagingApi _messagingApi;

  @override
  void initState() {
    super.initState();
    _messagingApi = MessagingApi();
    _messagingApi.sendMessage("Hello, platform!");
    _messagingApi.getMessage().then((message) {
      print("Received message: $message");
    });
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Auto Pigeon Demo'),
        ),
        body: Center(
          child: Text('Check the console for platform messages.'),
        ),
      ),
    );
  }
}

这样，你就完成了使用auto_pigeon插件在Flutter项目中自动生成跨平台通信代码的过程。确保在运行Flutter应用之前，已经正确实现了所有平台端的代码。