【Flutter】三个Channel(Android-java / Ios-swift)

Channel

实现与原生通信

【1】MethodChannel

flutter MethodChannel官方文档
通过MethodChannel来传递数据，调用方法

案例

分别调用Android和Ios原生的获取电量的方法

Flutter端

实例一个MethodChannel，唯一标识name，定义方法名称getBatteryLevel
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methodchannel.invokeMethod(name)来调用方法

  static const platform = MethodChannel('sample.flutter.dev/battery');static const method = 'getBatteryLevel';String _batteryLevel = 'Unknown battery level';Future<void> _getBatteryLevel() async {String batteryLevel;try {final result = await platform.invokeMethod<int>(method);batteryLevel = 'Battery level at $result';} on PlatformException catch (e) {batteryLevel = "Failed to get battery level: '${e.message}";}setState(() {_batteryLevel = batteryLevel;});}

界面操作

  @overrideWidget build(BuildContext context) {return Material(child: Column(mainAxisAlignment: MainAxisAlignment.spaceEvenly,children: [ElevatedButton(onPressed: _getBatteryLevel,child: const Text('Get Battery Level'),),Text(_batteryLevel),],),);}

Android端

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    private static final String CHANNEL = "sample.flutter.dev/battery";private MethodChannel methodChannel;private static final String METHOD = "getBatteryLevel";@Overridepublic void configureFlutterEngine(@NonNull FlutterEngine flutterEngine) {super.configureFlutterEngine(flutterEngine);BinaryMessenger binaryMessenger = flutterEngine.getDartExecutor().getBinaryMessenger();methodChannel = new MethodChannel(binaryMessenger, CHANNEL);methodChannel.setMethodCallHandler((call, result) -> {});}

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if (call.method.equals(METHOD)) {int batteryLevel = getBatteryLevel();if (batteryLevel != -1) {result.success(batteryLevel);} else {result.error("UNAVAILABLE", "Battery level not avaiable", null);}} else {result.notImplemented();}

private int getBatteryLevel() {int batteryLevel = -1;if (VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {BatteryManager batteryManager = (BatteryManager) getSystemService(BATTERY_SERVICE);batteryLevel = batteryManager.getIntProperty(BatteryManager.BATTERY_PROPERTY_CAPACITY);} else {IntentFilter intentFilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);Intent intent = new ContextWrapper(getApplicationContext()).registerReceiver(null, intentFilter);batteryLevel = (intent.getIntExtra(BatteryManager.EXTRA_LEVEL, -1) * 100) /intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1);}return batteryLevel;}

Ios端

实例FlutterMethodChannel
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override func application(_ application: UIApplication,didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {let method : String = "getBatteryLevel"let controller : FlutterViewController = window?.rootViewController as! FlutterViewControllerlet batteryChannel = FlutterMethodChannel(name: "sample.flutter.dev/battery", binaryMessenger: controller.binaryMessenger)batteryChannel.setMethodCallHandler({(call: FlutterMethodCall, result: @escaping FlutterResult) -> Void inguard call.method == method else {result(FlutterMethodNotImplemented)return}self.receiveBatteryLevel(result: result)})GeneratedPluginRegistrant.register(with: self)return super.application(application, didFinishLaunchingWithOptions: launchOptions)}

定义获取电量的方法

func receiveBatteryLevel(result: FlutterResult) -> Void {let device = UIDevice.currentdevice.isBatteryMonitoringEnabled = trueif device.batteryState == UIDevice.BatteryState.unknown {result(FlutterError(code: "UNAVAILABLE", message: "Battery level not available.", details: nil))} else {result(Int(device.batteryLevel * 100))}}

运行测试

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【2】EventChannel

墙外的参考文章
区别MethodChannel，它是continuously
采用event streams

案例

在原生端(Android&Ios)会有个计时器，不停的传时间给Flutter端，Flutter端显示出来

Flutter端

实例一个EventChannel，唯一标识name
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  late EventChannel eventChannel;@overridevoid initState() {eventChannel = const EventChannel('timeHandlerEvent');super.initState();}

在Flutter注册监听
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Stream<String> get streamTimeFromNative =>eventChannel.receiveBroadcastStream().map((event) => event.toString());@overrideWidget build(BuildContext context) {return Scaffold(body: Center(child: StreamBuilder<String>(stream: streamTimeFromNative,builder: (BuildContext context, AsyncSnapshot<String> snapshot) {if (snapshot.hasData) {return Text('${snapshot.data}',style: Theme.of(context).textTheme.headlineMedium,);} else {return const CircularProgressIndicator();}},),),);}

Ios端

实例一个FlutterEventChannel，加上唯一标识timeHandlerEvent
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let controller : FlutterViewController = window?.rootViewController as! FlutterViewControllerlet eventChannel = FlutterEventChannel(name: "timeHandlerEvent", binaryMessenger: controller.binaryMessenger)

定义FlutterStreamHandler

class TimeHandler: NSObject, FlutterStreamHandler {func onCancel(withArguments arguments: Any?) -> FlutterError? {return nil}func onListen(withArguments arguments: Any?, eventSink: @escaping FlutterEventSink) -> FlutterError? {return nil}}

每间隔1秒发送一次当前时间

    class TimeHandler: NSObject, FlutterStreamHandler {var timer = Timer()private var eventSink: FlutterEventSink?func onCancel(withArguments arguments: Any?) -> FlutterError? {eventSink = nilreturn nil}func onListen(withArguments arguments: Any?, eventSink: @escaping FlutterEventSink) -> FlutterError? {self.eventSink = eventSinkself.timer = Timer.scheduledTimer(withTimeInterval: 1, repeats: true, block: {_ in let dateFormat = DateFormatter()dateFormat.dateFormat = "HH:mm:ss"let time = dateFormat.string(from: Date())eventSink(time)})return nil}}

注册监听

eventChannel.setStreamHandler(TimeHandler())

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Android端

new 一个EventChannel对象
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在channel注册一个stream Handler

        EventChannel.StreamHandler streamHandler = new EventChannel.StreamHandler() {@Overridepublic void onListen(Object arguments, EventChannel.EventSink events) {}@Overridepublic void onCancel(Object arguments) {}};eventChannel.setStreamHandler(streamHandler);

不断将当前时间返回
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EventChannel.StreamHandler streamHandler = new EventChannel.StreamHandler() {private final Handler handler = new Handler(Looper.getMainLooper());private EventChannel.EventSink eventSink = null;@Overridepublic void onListen(Object arguments, EventChannel.EventSink events) {eventSink = events;Runnable runnable = new Runnable() {@Overridepublic void run() {Locale locale = new Locale("zh", "CN");SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss", locale);String time = dateFormat.format(new Date());events.success(time);handler.postDelayed(this, 1000);}};handler.postDelayed(runnable, 1000);}@Overridepublic void onCancel(Object arguments) {eventSink = null;}};eventChannel.setStreamHandler(streamHandler);

运行测试

在建立好EventChannel之后，运行项目。
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获取到当前的时间，并且不停的

【3】BasicMessageChannel

参考文章
约定一种数据格式，来互相传递数据

案例

传递Map数据到Android/Ios端，再解析并返回数据到Flutter端

Flutter端

构建BasicMessageChannel，唯一标识name，约定数据格式StandardMessageCodec

static const messageChannel =BasicMessageChannel('basic_message_channel', StandardMessageCodec());

发送数据

Map<String, dynamic> message = {"name": "apple","time": "2024-04-09 12:30:00"};
messageChannel.send(arguments)

接收数据

Map reply = await messageChannel.send(arguments) as Map;

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Android 端

接收数据

messageChannel.setMessageHandler((message, reply) -> {});

发送数据

reply.reply(resultMap);

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package com.example.basic_message_channel_example;import android.os.Bundle;import androidx.annotation.NonNull;
import androidx.annotation.Nullable;import java.sql.Timestamp;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;import io.flutter.embedding.android.FlutterActivity;
import io.flutter.embedding.engine.FlutterEngine;
import io.flutter.plugin.common.BasicMessageChannel;
import io.flutter.plugin.common.BinaryMessenger;
import io.flutter.plugin.common.StandardMessageCodec;public class MainActivity extends FlutterActivity {@Overridepublic void configureFlutterEngine(@NonNull FlutterEngine flutterEngine) {super.configureFlutterEngine(flutterEngine);BinaryMessenger binaryMessenger = Objects.requireNonNull(getFlutterEngine()).getDartExecutor().getBinaryMessenger();BasicMessageChannel<Object> messageChannel = new BasicMessageChannel<Object>(binaryMessenger, "basic_message_channel", StandardMessageCodec.INSTANCE);messageChannel.setMessageHandler((message, reply) -> {Map<Object, Object> arguments = (Map<Object, Object>) message;assert message != null;String name = (String) arguments.get("name");assert name != null;if (name.equals("apple")) {Map<String, Object> resultMap = new HashMap<>();String timeStr = (String) arguments.get("time");Timestamp timestamp = Timestamp.valueOf(timeStr);resultMap.put("message", "i eat the " + name + " at " + timestamp.toString());resultMap.put("code", 200);reply.reply(resultMap);} else {Map<String, Object> resultMap = new HashMap<>();resultMap.put("message", "i dislike " + name);resultMap.put("code", 500);reply.reply(resultMap);}});}
}

Ios 端

构建通道

let controller : FlutterViewController = window?.rootViewController as! FlutterViewController
let basicMessageChannel = FlutterBasicMessageChannel(name: channelName, binaryMessenger: controller.binaryMessenger)

接收数据

      basicMessageChannel.setMessageHandler { message, reply in}

返回数据

reply(result)

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import UIKit
import Flutter@available(iOS 15.0, *)
@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {override func application(_ application: UIApplication,didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {let channelName : String = "basic_message_channel"let controller : FlutterViewController = window?.rootViewController as! FlutterViewControllerlet basicMessageChannel = FlutterBasicMessageChannel(name: channelName, binaryMessenger: controller.binaryMessenger)basicMessageChannel.setMessageHandler { message, reply inif let data = message as? Dictionary<String, Any> {let name: String = data["name"] as? String ?? ""if name == "apple" {let timeStr: String = data["time"] as? String ?? ""var message: String = "I eat the "message.append(name)message.append(" at ")message.append(timeStr)let result = ["code": 200, "message": message]reply(result)} else {var message = "I dislike "message.append(name)let result = ["code": 500, "message": message]reply(result)}}}GeneratedPluginRegistrant.register(with: self)return super.application(application, didFinishLaunchingWithOptions: launchOptions)}
}