【Flutter 混合開發】與原生通訊-EventChannel

Flutter 混合開發系列 包含以下：

• 嵌入原生View-Android
• 嵌入原生View-iOS
• 與原生通訊-MethodChannel
• 與原生通訊-BasicMessageChannel
• 與原生通訊-EventChannel
• 添加 Flutter 到 Android Activity
• 添加 Flutter 到 Android Fragment
• 添加 Flutter 到 iOS

每一個工做日分享一篇，歡迎關注、點贊及轉發。

EventChannel

Flutter 端

Flutter 端建立 EventChannel 通道，用於與原生端通訊：

var _eventChannel = EventChannel('com.flutter.guide.EventChannel');

com.flutter.guide.EventChannel 是 EventChannel 的名稱，原生端要與之對應。

監聽原生端發送的消息：

var _data;
  @override
  void initState() {
    super.initState();
    _eventChannel.receiveBroadcastStream().listen(_onData);
  }

  _onData(event){
    setState(() {
      _data = event;
    });
  }

Flutter 端完整代碼：

class EventChannelDemo extends StatefulWidget {
  @override
  _EventChannelDemoState createState() => _EventChannelDemoState();
}

class _EventChannelDemoState extends State<EventChannelDemo> {

  var _eventChannel = EventChannel('com.flutter.guide.EventChannel');
  var _data;
  @override
  void initState() {
    super.initState();
    _eventChannel.receiveBroadcastStream().listen(_onData);
  }

  _onData(event){
    setState(() {
      _data = event;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(),
      body: Center(
        child: Text('$_data'),
      ),
    );
  }
}

Android 端

android 下建立 EventChannelDemo：

class EventChannelDemo(var activity: Activity, messenger: BinaryMessenger):EventChannel.StreamHandler {
    private var channel: EventChannel
    private var index = 0
    private var events: EventChannel.EventSink? = null
    init {
        channel = EventChannel(messenger, "com.flutter.guide.EventChannel")
        channel.setStreamHandler(this)
        startTimer()
    }


    fun startTimer() {
        var timer = Timer().schedule(timerTask {
            index++
            var map = mapOf("name" to "laomeng${index}",
                    "age" to "${index}"
            )
            activity.runOnUiThread {
                events?.success(map)
            }

        }, 0, 1000)

    }

    override fun onListen(arguments: Any?, events: EventChannel.EventSink?) {
        this.events = events
    }

    override fun onCancel(arguments: Any?) {
        this.events = null
    }
}

events?.success(map) 方法是向 Flutter 端發送數據，此方法必須在主線程執行：

activity.runOnUiThread {
    events?.success(map)
}

在 MainActivity 啓動：

class MainActivity : FlutterActivity() {

    override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
        super.configureFlutterEngine(flutterEngine)
        EventChannelDemo(this,flutterEngine.dartExecutor.binaryMessenger)
        flutterEngine.plugins.add(MyPlugin())
    }
}

iOS 端

ios 下建立 MethodChannelDemo，按以下方式：

import Flutter
import UIKit

public class EventChannelDemo:NSObject, FlutterStreamHandler{
    
    var channel:FlutterEventChannel?
    var count =  0
    var events:FlutterEventSink?
    
    public override init() {
        super.init()
    }
    
    convenience init(messenger: FlutterBinaryMessenger) {
        
        self.init()
        
        channel = FlutterEventChannel(name: "com.flutter.guide.EventChannel", binaryMessenger: messenger)
        channel?.setStreamHandler(self)
        startTimer()
    }
    
    func startTimer() {
        let timer = Timer.scheduledTimer(timeInterval:1, target: self, selector:#selector(self.tickDown),userInfo:nil,repeats: true)
    }
    @objc func tickDown(){
        count += 1
        let args = ["count":count]
        if(events != nil){
            events!(args)
        }
    }
    
    public func onListen(withArguments arguments: Any?, eventSink events: @escaping FlutterEventSink) -> FlutterError? {
        self.events = events
        return nil;
    }
    
    public func onCancel(withArguments arguments: Any?) -> FlutterError? {
        self.events = nil
        return nil;
    }

}

在 AppDelegate 啓動：

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
    EventChannelDemo(messenger: controller.binaryMessenger)
    GeneratedPluginRegistrant.register(with: self)
    
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }
}

交流

老孟Flutter博客（330個控件用法+實戰入門系列文章）：http://laomengit.com

歡迎加入Flutter交流羣（微信：laomengit）、關注公衆號【老孟Flutter】：