9.1 平台通道（Platform Channel）

Platform Channel 是 Flutter 与原生平台（Android/iOS）之间通信的桥梁，允许 Dart 代码调用原生 API，或原生代码向 Flutter 推送事件。

一、通信机制概述

Flutter (Dart) Platform Channel 原生 (Java/Swift) │ │ │ MethodChannel.invokeMethod('getBatteryLevel') │ │ ─────────────────────────────────────────────────► │ │ │ 执行原生代码 │ result: 85 │ │ ◄───────────────────────────────────────────────── │ │ │ │ EventChannel.receiveBroadcastStream() │ │ ─────────────────────────────────────────────────► │ │ event: {charging: true} │ │ ◄───────────────────────────────────────────────── │ 原生推送事件

三种 Channel 类型：

二、MethodChannel

2.1 Flutter 侧

classBatteryService{staticconst_channel=MethodChannel('com.example.app/battery');staticFuture<int>getBatteryLevel()async{try{finallevel=await_channel.invokeMethod<int>('getBatteryLevel');returnlevel??-1;}onPlatformExceptioncatch(e){debugPrint('Battery error:${e.message}');return-1;}onMissingPluginException{debugPrint('Battery plugin not available');return-1;}}staticFuture<bool>isCharging()async{finalresult=await_channel.invokeMethod<bool>('isCharging');returnresult??false;}}

2.2 Android 侧（Kotlin）

// android/app/src/main/kotlin/.../MainActivity.ktclassMainActivity:FlutterActivity(){privatevalCHANNEL="com.example.app/battery"overridefunconfigureFlutterEngine(flutterEngine:FlutterEngine){super.configureFlutterEngine(flutterEngine)MethodChannel(flutterEngine.dartExecutor.binaryMessenger,CHANNEL).setMethodCallHandler{call,result->when(call.method){"getBatteryLevel"->{vallevel=getBatteryLevel()if(level!=-1)result.success(level)elseresult.error("UNAVAILABLE","Battery not available",null)}"isCharging"->{result.success(isDeviceCharging())}else->result.notImplemented()}}}privatefungetBatteryLevel():Int{valbatteryManager=getSystemService(BATTERY_SERVICE)asBatteryManagerreturnbatteryManager.getIntProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY)}}

2.3 iOS 侧（Swift）

// ios/Runner/AppDelegate.swift@UIApplicationMain@objcclassAppDelegate:FlutterAppDelegate{overridefuncapplication(_application:UIApplication,didFinishLaunchingWithOptions options:[UIApplication.LaunchOptionsKey:Any]?)->Bool{letcontroller=window?.rootViewControlleras!FlutterViewControllerletchannel=FlutterMethodChannel(name:"com.example.app/battery",binaryMessenger:controller.binaryMessenger)channel.setMethodCallHandler{call,resultinswitchcall.method{case"getBatteryLevel":letdevice=UIDevice.current device.isBatteryMonitoringEnabled=trueifdevice.batteryState==.unknown{result(FlutterError(code:"UNAVAILABLE",message:"Battery not available",details:nil))}else{result(Int(device.batteryLevel*100))}default:result(FlutterMethodNotImplemented)}}returnsuper.application(application,didFinishLaunchingWithOptions:options)}}

三、EventChannel

3.1 Flutter 侧（监听流）

classNetworkStatusService{staticconst_channel=EventChannel('com.example.app/network');staticStream<bool>getonConnectivityChanged{return_channel.receiveBroadcastStream().map((event)=>eventasbool);}}// 使用classConnectivityWidgetextendsStatefulWidget{...}class_StateextendsState<ConnectivityWidget>{StreamSubscription?_sub;bool _isConnected=true;@overridevoidinitState(){super.initState();_sub=NetworkStatusService.onConnectivityChanged.listen((connected){setState(()=>_isConnected=connected);});}@overridevoiddispose(){_sub?.cancel();super.dispose();}}

3.2 Android 侧（Kotlin）

classConnectivityStreamHandler(context:Context):EventChannel.StreamHandler{privatevalconnectivityManager=context.getSystemService(Context.CONNECTIVITY_SERVICE)asConnectivityManagerprivatevarcallback:ConnectivityManager.NetworkCallback?=nulloverridefunonListen(arguments:Any?,events:EventChannel.EventSink){callback=object:ConnectivityManager.NetworkCallback(){overridefunonAvailable(network:Network){events.success(true)}overridefunonLost(network:Network){events.success(false)}}connectivityManager.registerDefaultNetworkCallback(callback!!)}overridefunonCancel(arguments:Any?){callback?.let{connectivityManager.unregisterNetworkCallback(it)}callback=null}}

四、BasicMessageChannel

// 双向通信（不需要请求-响应模式，适合消息传递）staticconst_messageChannel=BasicMessageChannel<String>('com.example.app/messages',StringCodec(),);// 发送消息到原生await_messageChannel.send('Hello from Flutter');// 监听来自原生的消息_messageChannel.setMessageHandler((message)async{print('Message from native:$message');return'Flutter received:$message';// 可选的回复});

小结

👉 下一节：9.2 原生插件开发