flutter使用Chanel与原生通信
在Flutter中，Platform Channel允许Flutter与原生平台（如Android和iOS）之间进行双向通信，以便在Flutter应用程序和原生代码之间传递消息和调用功能。
以下是使用Platform Channel与原生通信的一般步骤：
1. 在Flutter端创建一个MethodChannel对象，用于发送消息给原生平台。通常在Flutter Widget的初始化方法中创建MethodChannel。
import 'package:flutter/services.dart';// 创建MethodChannel对象
MethodChannel _channel = MethodChannel('com.example.channelName');
2. 在Flutter端发送消息给原生平台，可以使用MethodChannel的invokeMethod方法。
// 发送消息给原生平台
dynamic result = await _channel.invokeMethod('methodName', arguments);
3. 在原生平台（如Android和iOS）实现对应的方法，用于接收Flutter端发送的消息。
对于Android平台，可以在MainActivity或Application类中注册MethodChannel，并实现对应的方法。
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.channelName";@Overridepublic void configureFlutterEngine(FlutterEngine flutterEngine) {super.configureFlutterEngine(flutterEngine);new MethodChannel(flutterEngine.getDartExecutor().getBinaryMessenger(), CHANNEL).setMethodCallHandler((call, result) -> {if (call.method.equals("methodName")) {// 处理Flutter端发送的消息String arg = call.arguments.toString();// 执行相应的操作// ...// 将结果返回给Flutter端result.success("Result from native");} else {result.notImplemented();}});}
}
对于iOS平台，在AppDelegate.m文件中注册MethodChannel，并实现对应的方法。
#import "AppDelegate.h"
#import "GeneratedPluginRegistrant.h"@implementation AppDelegate- (BOOL)application:(UIApplication *)applicationdidFinishLaunchingWithOptions:(NSDictionary *)launchOptions {[GeneratedPluginRegistrant registerWithRegistry:self];FlutterViewController *controller = (FlutterViewController *)self.window.rootViewController;FlutterMethodChannel *channel = [FlutterMethodChannelmethodChannelWithName:@"com.example.channelName"binaryMessenger:controller.binaryMessenger];[channel setMethodCallHandler:^(FlutterMethodCall* call, FlutterResult result) {if ([@"methodName" isEqualToString:call.method]) {// 处理Flutter端发送的消息NSString *arg = call.arguments;// 执行相应的操作// ...// 将结果返回给Flutter端result(@"Result from native");} else {result(FlutterMethodNotImplemented);}}];return [super application:application didFinishLaunchingWithOptions:launchOptions];
}通过以上步骤，你可以在Flutter端和原生代码之间进行双向通信。
以下是我项目初期的调研代码块：
flutter的代码：
class GetxStatePage extends StatefulWidget {const GetxStatePage({super.key});@overrideState<StatefulWidget> createState() {return GetxStatePageState();}
}class GetxStatePageState extends State<GetxStatePage> {late MethodChannel _channel;@overridevoid initState() {super.initState();//初始化MethodChannel，通道名称“multiple-flutters”，Android端ios也要统一_channel = const MethodChannel('multiple-flutters');}@overrideWidget build(BuildContext context) {return MaterialApp(home: Scaffold(appBar: AppBar(backgroundColor: SGColors.white,title: const Text('Getx',style: TextStyle(color: SGColors.textColor),),),body: Center(child: InkWell(onTap: () {String value = "Hello from Flutter";//这里定义方法和参数_channel.invokeMethod<void>("nextData", {'data': value});// 在此处添加您希望执行的点击事件print('跳转到Android');},child: SizedBox(width: 100,height: 100,child: Text("Getx"),),),),),);}
}
我们再看看Android端的实现代码：首先打通通道需要engine，channel，与flutter端的统一就行；
class EngineBindings(activity: Activity, delegate: EngineBindingsDelegate, entrypoint: String,initialRoute: String) :DataModelObserver {val channel: MethodChannelval engine: FlutterEngineval delegate: EngineBindingsDelegateinit {// This has to be lazy to avoid creation before the FlutterEngineGroup.val dartEntrypoint =DartExecutor.DartEntrypoint(FlutterInjector.instance().flutterLoader().findAppBundlePath(), entrypoint)// engine = BaseApplication.getApplication().engines.createAndRunEngine(activity, dartEntrypoint)engine = BaseApplication.getApplication().engines.createAndRunEngine(activity, dartEntrypoint, initialRoute)this.delegate = delegatechannel = MethodChannel(engine.dartExecutor.binaryMessenger, "multiple-flutters")}/*** This setups the messaging connections on the platform channel and the DataModel.*/fun attach() {DataModel.instance.addObserver(this)channel.invokeMethod("setCount", DataModel.instance.counter)channel.setMethodCallHandler { call, result ->when (call.method) {"incrementCount" -> {DataModel.instance.counter = DataModel.instance.counter + 1result.success(null)}"next" -> {this.delegate.onNext()result.success(null)}"nextData" -> {val data: String? = call.argument("data")this.delegate.onNext(data)result.success(null)}else -> {result.notImplemented()}}}}/*** This tears down the messaging connections on the platform channel and the DataModel.*/fun detach() {engine.destroy();DataModel.instance.removeObserver(this)channel.setMethodCallHandler(null)}override fun onCountUpdate(newCount: Int) {channel.invokeMethod("setCount", newCount)}}
具体的activity必须继承FlutterActivity，且这个类必须在主配置清单AndroidMainfest.xml中配置：
<activityandroid:name=".ui.demo.SingleFlutterActivity"android:configChanges="orientation|keyboardHidden|keyboard|screenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"android:exported="true"android:hardwareAccelerated="true"android:windowSoftInputMode="adjustResize" />
class FlutterToAndroidActivity : FlutterActivity(), EngineBindingsDelegate {var mFlutterApi: SGAndroid2Flutter? = nullprivate val engineBindings: EngineBindings by lazy {EngineBindings(activity = this, delegate = this, entrypoint = FlutterRouter.MESSAGE_CENTER_ENTRY_POINTER, initialRoute = "${FlutterRouter.MESSAGE_CENTER_ROUTER}?psId=1234")}override fun onDestroy() {super.onDestroy()engineBindings.detach()}override fun provideFlutterEngine(context: Context): FlutterEngine? {return engineBindings.engine}override fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)engineBindings.attach()setContentView(layout.activity_flutter_to_android)val extraString = intent.getStringExtra("extraString")tv_center.text = extraStringval binaryMessenger: BinaryMessenger = provideFlutterEngine(this)!!.getDartExecutor().getBinaryMessenger()mFlutterApi = SGAndroid2Flutter(binaryMessenger)tv_center.setOnClickListener {callFlutterMethod()}}private fun callFlutterMethod() {val handler = Handler(Looper.getMainLooper())(0..2).map { it.toLong() * 100 }.forEach {handler.postDelayed(it) {mFlutterApi?.sendData(it.toString()) { // 必须在主线程中调用println("从 Flutter 获取到的值是：$it ") // true，回调在主线程}}}}override fun onNext() {}override fun onNext(str: String?) {}
}
就可以在onNext的方法中调用我们的操作；
/*** flutter 调用原生的方法,原生写法* */override fun onNext(str: String?) {val flutterIntent = Intent(this, FlutterToAndroidActivity::class.java)flutterIntent.putExtra("extraString", str)startActivity(flutterIntent)
}
最后执行，flutter跳转FlutterToAndroidActivity成功，flutter成功调用原生Android的方法。
体会：
之前一直使用纯flutter开发，当需要原生加flutter开发的时候，其实成本更大了。
他既需要Android写好桥接代码，又需要ios写一套，flutter端的是一套。
为什么会这样？因为船大难掉头，一些大的现有项目没办法短时间改技术栈，一些公司会拿出一部分试试水。部分代码迁移。为以后的项目打基础。
遇到些特殊的需求，会更麻烦，比如我们这种做法：需要在原生端获取网络数据，去请求接口，然后把数据传递给flutter，而一开始请求哪个接口，传哪些参数又需要flutter传给原生，Android和ios两端去实现。
所以在项目中我们用到了pigeon的插件，这样就不用写太多的代码，通信的过程pigeon会帮你自动生成，可以看我下一篇文章实践！
https://juejin.cn/post/7270861556031700992