面试题：Flutter嵌入层与原生平台集成之通信实现

Question

在Flutter嵌入原生平台时，简述如何使用MethodChannel实现Flutter与原生（以Android为例）之间的双向通信，分别说明在Flutter端和Android端需要进行哪些关键步骤和代码实现。

Answer 1

Flutter端

1. 导入依赖：在pubspec.yaml文件中确保flutter库已引入，通常默认包含。
2. 创建MethodChannel：在Flutter代码中创建MethodChannel实例，指定通道名称，该名称需与Android端一致。

import 'package:flutter/services.dart';

const platform = MethodChannel('com.example.flutter_native_channel');

3. 调用原生方法：使用invokeMethod方法调用Android端暴露的方法，并可传递参数。

try {
  final String result = await platform.invokeMethod('getPlatformVersion');
  print('来自原生的结果: $result');
} on PlatformException catch (e) {
  print("调用原生方法出错: ${e.message}");
}

4. 接收原生调用：注册一个方法处理程序，处理来自Android端的调用。

platform.setMethodCallHandler((call) async {
  if (call.method == 'flutterMethod') {
    // 处理来自原生的调用
    return 'Flutter处理结果';
  }
  throw PlatformException(code: 'Unimplemented', message: '该方法未实现');
});

Android端

1. 导入依赖：在app/build.gradle文件中确保flutter相关依赖已配置。

dependencies {
    implementation "io.flutter:flutter_embedding_v2_release:1.0.0"
}

2. 创建MethodChannel：在Android代码中创建MethodChannel实例，指定与Flutter端相同的通道名称。

import io.flutter.embedding.android.FlutterActivity;
import io.flutter.embedding.engine.FlutterEngine;
import io.flutter.plugin.common.MethodChannel;

public class MainActivity extends FlutterActivity {
    private static final String CHANNEL = "com.example.flutter_native_channel";

    @Override
    public void configureFlutterEngine(FlutterEngine flutterEngine) {
        super.configureFlutterEngine(flutterEngine);
        new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL)
              .setMethodCallHandler(
                    (call, result) -> {
                        if (call.method.equals("getPlatformVersion")) {
                            String platformVersion = "Android " + android.os.Build.VERSION.RELEASE;
                            result.success(platformVersion);
                        } else {
                            result.notImplemented();
                        }
                    }
            );
    }
}

3. 调用Flutter方法：通过MethodChannel的invokeMethod方法调用Flutter端暴露的方法。

MethodChannel channel = new MethodChannel(getFlutterEngine().getDartExecutor().getBinaryMessenger(), CHANNEL);
channel.invokeMethod("flutterMethod", null, new MethodChannel.Result() {
    @Override
    public void success(Object o) {
        Log.d("Native", "Flutter返回结果: " + o);
    }

    @Override
    public void error(String s, String s1, Object o) {
        Log.e("Native", "调用Flutter方法出错: " + s1);
    }

    @Override
    public void notImplemented() {
        Log.e("Native", "该方法未实现");
    }
});