【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

  @override
  Widget 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";

    @Override
    public 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! FlutterViewController
      let batteryChannel = FlutterMethodChannel(name: "sample.flutter.dev/battery", binaryMessenger: controller.binaryMessenger)
      batteryChannel.setMethodCallHandler({
          (call: FlutterMethodCall, result: @escaping FlutterResult) -> Void in
          guard 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.current
        device.isBatteryMonitoringEnabled = true
        if 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;

  @override
  void 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());

  @override
  Widget 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! FlutterViewController
      let 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 = nil
            return nil
        }
        
        func onListen(withArguments arguments: Any?, eventSink: @escaping FlutterEventSink) -> FlutterError? {
            self.eventSink = eventSink
            self.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() {
            @Override
            public void onListen(Object arguments, EventChannel.EventSink events) {
            }

            @Override
            public 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;

            @Override
            public void onListen(Object arguments, EventChannel.EventSink events) {
                eventSink = events;
                Runnable runnable = new Runnable() {
                    @Override
                    public 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);
            }

            @Override
            public 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 {

    @Override
    public 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! FlutterViewController
      let basicMessageChannel = FlutterBasicMessageChannel(name: channelName, binaryMessenger: controller.binaryMessenger)
      basicMessageChannel.setMessageHandler { message, reply in
          if 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)
  }
}