Flutter 混合开发系列 包含如下：
嵌入原生View-Android嵌入原生View-iOS与原生通信-MethodChannel与原生通信-BasicMessageChannel与原生通信-EventChannel添加 Flutter 到 Android Activity添加 Flutter 到 Android Fragment添加 Flutter 到 iOS每个工作日分享一篇，欢迎关注、点赞及转发。
平台通信的3中方式
Flutter 与 Native 端通信有如下3个方法：
MethodChannel：Flutter 与 Native 端相互调用，调用后可以返回结果，可以 Native 端主动调用，也可以Flutter主动调用，属于双向通信。此方式为最常用的方式， Native 端调用需要在主线程中执行。BasicMessageChannel：用于使用指定的编解码器对消息进行编码和解码，属于双向通信，可以 Native 端主动调用，也可以Flutter主动调用。EventChannel：用于数据流（event streams）的通信， Native 端主动发送数据给 Flutter，通常用于状态的监听，比如网络变化、传感器数据等。通信架构图
此图为官方的架构图
Flutter 与 Native 端通信是异步的。
通信与平台线程
Native 端主动发送数据给 Flutter时，Native 端代码需要在主线程中执行，Android 端从子线程跳转到主线程方式：
Kotlin 代码：
Handler(Looper.getMainLooper()).post { }Java 代码：
new Handler(Looper.getMainLooper()).post(new Runnable() { @Override public void run() { } });如果可以获取到当前 Activity，也可以使用如下方式：
activity.runOnUiThread { }iOS 端从子线程跳转到主线程方式：
Objective-C 代码：
dispatch_async(dispatch_get_main_queue(), ^{ });Swift 代码：
DispatchQueue.main.async { }Flutter 端
Flutter 端创建 MethodChannel 通道，用于与原生端通信：
var channel = MethodChannel('com.flutter.guide.MethodChannel');com.flutter.guide.MethodChannel 是 MethodChannel 的名称，原生端要与之对应。
发送消息：
var result = await channel.invokeMethod('sendData',{'name': 'laomeng', 'age': 18}) 第一个参数表示method，方法名称，原生端会解析此参数。第二个参数表示参数，类型任意，多个参数通常使用Map。返回 Future，原生端返回的数据。完整代码：
class MethodChannelDemo extends StatefulWidget { @override _MethodChannelDemoState createState() => _MethodChannelDemoState(); } class _MethodChannelDemoState extends State<MethodChannelDemo> { var channel = MethodChannel('com.flutter.guide.MethodChannel'); var _data; @override Widget build(BuildContext context) { return Scaffold( appBar: AppBar(), body: Column( children: [ SizedBox( height: 50, ), RaisedButton( child: Text('发送数据到原生'), onPressed: () async { var result = await channel .invokeMethod('sendData', {'name': 'laomeng', 'age': 18}); var name = result['name']; var age = result['age']; setState(() { _data = '$name,$age'; }); }, ), Text('原生返回数据：$_data') ], ), ); } }Android 端
android 下创建 MethodChannelDemo：
package com.flutter.guide import io.flutter.plugin.common.BinaryMessenger import io.flutter.plugin.common.MethodCall import io.flutter.plugin.common.MethodChannel /** * des: */ class MethodChannelDemo(messenger: BinaryMessenger): MethodChannel.MethodCallHandler { private var channel: MethodChannel init { channel = MethodChannel(messenger, "com.flutter.guide.MethodChannel") channel.setMethodCallHandler(this) } override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) { } }onMethodCall 方法在 Flutter 端调用 invokeMethod 方法回调，解析方法如下：
override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) { if (call.method == "sendData") { val name = call.argument("name") as String? val age = call.argument("age") as Int? var map = mapOf("name" to "hello,$name", "age" to "$age" ) result.success(map) } } call.method 字符串就是 invokeMethod 方法传入的 method。call.argument 是 invokeMethod 传入的参数，由于 Flutter 端传入的是 Map，所以上面的解析按照 Map 解析。result.success() 是返回给 Flutter 的结果。Flutter 端解析：
var result = await channel .invokeMethod('sendData', {'name': 'laomeng', 'age': 18}); var name = result['name']; var age = result['age']; 两端的解析要相互对应。在 MainActivity 启动：
class MainActivity : FlutterActivity() { override fun configureFlutterEngine(flutterEngine: FlutterEngine) { super.configureFlutterEngine(flutterEngine) MethodChannelDemo(flutterEngine.dartExecutor.binaryMessenger) } }iOS 端
ios 下创建 MethodChannelDemo，按如下方式：
import Flutter import UIKit public class MethodChannelDemo { init(messenger: FlutterBinaryMessenger) { let channel = FlutterMethodChannel(name: "com.flutter.guide.MethodChannel", binaryMessenger: messenger) channel.setMethodCallHandler { (call:FlutterMethodCall, result:@escaping FlutterResult) in if (call.method == "sendData") { if let dict = call.arguments as? Dictionary<String, Any> { let name:String = dict["name"] as? String ?? "" let age:Int = dict["age"] as? Int ?? -1 result(["name":"hello,\(name)","age":age]) } } } } }在 AppDelegate 启动：
import UIKit import Flutter @UIApplicationMain @objc class AppDelegate: FlutterAppDelegate { override func application( _ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]? ) -> Bool { let controller : FlutterViewController = window?.rootViewController as! FlutterViewController MethodChannelDemo(messenger: controller.binaryMessenger) GeneratedPluginRegistrant.register(with: self) return super.application(application, didFinishLaunchingWithOptions: launchOptions) } }原生端主动发送消息给Flutter
Flutter 端接收数据
@override void initState() { super.initState(); channel.setMethodCallHandler((call) { setState(() { _nativeData = call.arguments['count']; }); }); }Android 发送数据
原生端启动定时器，每隔一秒向 Flutter 发送数据，Android 端代码：
class MethodChannelDemo(var activity: Activity, messenger: BinaryMessenger) : MethodChannel.MethodCallHandler { private var channel: MethodChannel private var count = 0 init { channel = MethodChannel(messenger, "com.flutter.guide.MethodChannel") channel.setMethodCallHandler(this) startTimer() } fun startTimer() { var timer = Timer().schedule(timerTask { activity.runOnUiThread { var map = mapOf("count" to count++) channel.invokeMethod("timer", map) } }, 0, 1000) } override fun onMethodCall(call: MethodCall, result: MethodChannel.Result) { if (call.method == "sendData") { val name = call.argument("name") as String? val age = call.argument("age") as Int? var map = mapOf("name" to "hello,$name", "age" to "$age" ) result.success(map) } } }注意：Android 端发送数据要在主现场中调用，即：
activity.runOnUiThread { var map = mapOf("count" to count++) channel.invokeMethod("timer", map) }启动修改如下：
class MainActivity : FlutterActivity() { override fun configureFlutterEngine(flutterEngine: FlutterEngine) { super.configureFlutterEngine(flutterEngine) MethodChannelDemo(this,flutterEngine.dartExecutor.binaryMessenger) flutterEngine.plugins.add(MyPlugin()) } }iOS 发送数据
iOS 端启动定时器代码如下：
import Flutter import UIKit public class MethodChannelDemo { var count = 0 var channel:FlutterMethodChannel init(messenger: FlutterBinaryMessenger) { channel = FlutterMethodChannel(name: "com.flutter.guide.MethodChannel", binaryMessenger: messenger) channel.setMethodCallHandler { (call:FlutterMethodCall, result:@escaping FlutterResult) in if (call.method == "sendData") { if let dict = call.arguments as? Dictionary<String, Any> { let name:String = dict["name"] as? String ?? "" let age:Int = dict["age"] as? Int ?? -1 result(["name":"hello,\(name)","age":age]) } } } startTimer() } func startTimer() { var timer = Timer.scheduledTimer(timeInterval:1, target: self, selector:#selector(self.tickDown),userInfo:nil,repeats: true) } @objc func tickDown(){ count += 1 var args = ["count":count] channel.invokeMethod("timer", arguments:args) } }