在Flutter中调用Android的代码

在Flutter中调用Android原生代码通常涉及以下步骤：

1. 创建一个继承自MethodChannel.MethodCallHandler的FlutterPlugin类。
2. 实现onAttachedToEngine和onDetachedFromEngine方法，以管理插件的生命周期。
3. 在onAttachedToEngine方法中，注册处理来自Flutter的方法调用的处理程序。
4. 使用MethodChannel与Flutter端进行通信。
5. 在Android的MainActivity类中，使用GeneratedPluginRegistrant.registerWith来自动注册所有的插件。

以下是一个简单的例子：

Android端：

import io.flutter.embedding.engine.plugins.FlutterPlugin;
import io.flutter.plugin.common.MethodCall;
import io.flutter.plugin.common.MethodChannel;
import io.flutter.plugin.common.PluginRegistry.Registrar;
 
public class MyPlugin implements FlutterPlugin, MethodChannel.MethodCallHandler {
  private MethodChannel channel;
 
  @Override
  public void onAttachedToEngine(@NonNull FlutterPluginBinding flutterPluginBinding) {
    channel = new MethodChannel(flutterPluginBinding.getBinaryMessenger(), "my_plugin");
    channel.setMethodCallHandler(this);
  }
 
  @Override
  public void onMethodCall(@NonNull MethodCall call, @NonNull MethodChannel.Result result) {
    if (call.method.equals("getPlatformVersion")) {
      result.success("Android " + android.os.Build.VERSION.RELEASE);
    } else {
      result.notImplemented();
    }
  }
 
  @Override
  public void onDetachedFromEngine(@NonNull FlutterPluginBinding binding) {
    channel.setMethodCallHandler(null);
  }
 
  public static void registerWith(Registrar registrar) {
    final MethodChannel channel = new MethodChannel(registrar.messenger(), "my_plugin");
    channel.setMethodCallHandler(new MyPlugin());
  }
}

iOS端（Swift）：

import Flutter
import UIKit
 
public class SwiftMyPlugin: NSObject, FlutterPlugin {
  public static func register(with registrar: FlutterPluginRegistrar) {
    let channel = FlutterMethodChannel(name: "my_plugin", binaryMessenger: registrar.messenger())
    let instance = SwiftMyPlugin()
    registrar.addMethodCallDelegate(instance, channel: channel)
  }
 
  public func handle(_ call: FlutterMethodCall, result: @escaping FlutterResult) {
    if call.method == "getPlatformVersion" {
      result(UIDevice.current.systemVersion)
    } else {
      result(FlutterMethodNotImplemented)
    }
  }
}

在Flutter端调用：

import 'package:flutter/services.dart';
 
class MyPlugin {
  static const MethodChannel _channel = Me