Flutter构建与发送功能插件build_and_send的使用

当然，下面是一个关于如何在Flutter项目中构建和使用一个简单的build_and_send插件的示例代码。这个插件将实现一个简单的文本构建和发送功能。为了简化示例，我们将使用Dart的原生代码和Flutter平台通道（Platform Channels）来实现这一功能。

1. 创建Flutter插件项目

首先，你需要一个Flutter项目。如果你还没有Flutter项目，可以使用以下命令创建一个新的Flutter项目：

flutter create my_flutter_app
cd my_flutter_app

2. 创建自定义插件

在Flutter项目的根目录下，创建一个新的插件目录，例如build_and_send：

mkdir plugins/build_and_send
cd plugins/build_and_send
flutter create --template=plugin --org=com.example --platforms=android,ios .

这将创建一个基本的Flutter插件结构。

3. 实现插件的Dart代码

在plugins/build_and_send/lib/build_and_send.dart中，编写插件的Dart代码：

import 'dart:async';

import 'package:flutter/services.dart';

class BuildAndSend {
  static const MethodChannel _channel = const MethodChannel('com.example.build_and_send');

  static Future<String?> buildMessage(String message) async {
    final String? result = await _channel.invokeMethod('buildMessage', message);
    return result;
  }

  static Future<void> sendMessage(String message) async {
    try {
      await _channel.invokeMethod('sendMessage', message);
    } on PlatformException catch (e) {
      print("Failed to send message: '${e.message}'.");
    }
  }
}

4. 实现Android原生代码

在plugins/build_and_send/android/src/main/kotlin/com/example/build_and_send/BuildAndSendPlugin.kt中，编写Android原生代码：

package com.example.build_and_send

import android.content.Context
import androidx.annotation.NonNull
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.MethodChannel
import io.flutter.plugin.common.MethodCall
import io.flutter.plugin.common.MethodChannel.MethodCallHandler
import io.flutter.plugin.common.MethodChannel.Result

class BuildAndSendPlugin: FlutterPlugin, MethodCallHandler, ActivityAware {
  private var channel: MethodChannel? = null
  private var context: Context? = null

  override fun onAttachedToEngine(@NonNull flutterPluginBinding: FlutterPluginBinding) {
    channel = MethodChannel(flutterPluginBinding.binaryMessenger, "com.example.build_and_send")
    channel?.setMethodCallHandler(this)
    context = flutterPluginBinding.applicationContext
  }

  override fun onMethodCall(@NonNull call: MethodCall, @NonNull result: Result) {
    if (call.method == "buildMessage") {
      val message = call.argument<String>("message") ?: ""
      result.success("Processed message: $message")
    } else if (call.method == "sendMessage") {
      val message = call.argument<String>("message") ?: ""
      // Here you can add the actual logic to send the message, e.g., via network, SMS, etc.
      // For simplicity, we'll just print it to the log.
      println("Sending message: $message")
      result.success(null)
    } else {
      result.notImplemented()
    }
  }

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

  override fun onAttachedToActivity(binding: ActivityPluginBinding) {
    // This method is optional
  }

  override fun onDetachedFromActivityForConfigChanges() {
    // This method is optional
  }

  override fun onReattachedToActivityForConfigChanges(binding: ActivityPluginBinding) {
    // This method is optional
  }

  override fun onDetachedFromActivity() {
    // This method is optional
  }
}

5. 实现iOS原生代码

在plugins/build_and_send/ios/Classes/BuildAndSendPlugin.swift中，编写iOS原生代码：

import Flutter

public class BuildAndSendPlugin: NSObject, FlutterPlugin, MethodCallHandler {
  public static func register(with registrar: FlutterPluginRegistrar) {
    let channel = FlutterMethodChannel(name: "com.example.build_and_send", binaryMessenger: registrar.messenger())
    let instance = BuildAndSendPlugin()
    registrar.addMethodCallDelegate(instance, channel: channel)
  }

  public func handle(_ call: FlutterMethodCall, result: @escaping FlutterResult) {
    switch call.method {
    case "buildMessage":
      guard let message = call.arguments as? String else {
        result("Invalid argument")
        return
      }
      result("Processed message: \(message)")
    case "sendMessage":
      guard let message = call.arguments as? String else {
        result("Invalid argument")
        return
      }
      // Here you can add the actual logic to send the message, e.g., via network, SMS, etc.
      // For simplicity, we'll just print it to the log.
      print("Sending message: \(message)")
      result(())
    default:
      result(FlutterMethodNotImplemented)
    }
  }
}

6. 在Flutter项目中使用插件

回到你的Flutter项目根目录，编辑pubspec.yaml文件，添加对本地插件的依赖：

dependencies:
  flutter:
    sdk: flutter
  build_and_send:
    path: ./plugins/build_and_send

然后，在lib/main.dart中，使用你的插件：

import 'package:flutter/material.dart';
import 'package:build_and_send/build_and_send.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('Build and Send Example'),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              Text(
                'Hello, Flutter!',
                style: TextStyle(fontSize: 20),
              ),
              ElevatedButton(
                onPressed: () async {
                  String? processedMessage = await BuildAndSend.buildMessage("Hello, World!");
                  print(processedMessage ?? "Failed to process message");
                  await BuildAndSend.sendMessage("Hello, World!");
                },
                child: Text('Build and Send Message'),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

7. 运行Flutter项目

确保你已经连接了Android设备或启动了iOS模拟器，然后运行以下命令来构建和运行你的Flutter项目：

flutter run

这样，你就可以在Flutter应用中调用BuildAndSend插件来构建和发送消息了。