Flutter和原生交互---EventChannel

Posted 2022-11-03 泸沽烟火

EventChannel，用于android原生事件流向Flutter端的发送，例如通过原生监听重力感应等状态变化后向Flutter发送通知，一对多通知，类似于原生广播

原生端实现代码：

1.实现EventChannel：单例类，通过sendEventData通知Flutter

package com.example.flutter_event_channel_plugin;

import android.util.Log;

import androidx.annotation.NonNull;

import io.flutter.embedding.engine.plugins.FlutterPlugin;
import io.flutter.plugin.common.EventChannel;

public class FlutterEventChannel implements FlutterPlugin, EventChannel.StreamHandler 
    public static final String CHANNEL_NAME = "event_channel_name";
    private EventChannel eventChannel;
    private EventChannel.EventSink eventSink;

    private static volatile FlutterEventChannel instance;

    private FlutterEventChannel () 
    

    public static FlutterEventChannel getInstance() 
        if (instance == null) 
            synchronized (FlutterEventChannel .class) 
                if (instance == null) 
                    instance = new FlutterEventChannel ();
                
            
        
        return instance;
    

    /**
     * 处理设置事件流的请求。
     *
     * @param arguments 流配置参数，可能为空。
     * @param events    用于向flutter接收器发射事件。
     */
    @Override
    public void onListen(Object arguments, EventChannel.EventSink events) 
        this.eventSink = events;
    

    /**
     * 处理请求以删除最近创建的事件流。
     *
     * @param arguments 流配置参数，可能为空。
     */
    @Override
    public void onCancel(Object arguments) 

    

    public void sendEventData(Object data) 
        if (eventSink != null) 
            eventSink.success(data);
        
    

    @Override
    public void onAttachedToEngine(@NonNull FlutterPlugin.FlutterPluginBinding binding) 
        eventChannel = new EventChannel(binding.getBinaryMessenger(), CHANNEL_NAME);
        eventChannel.setStreamHandler(this);
    

    @Override
    public void onDetachedFromEngine(@NonNull FlutterPlugin.FlutterPluginBinding binding) 
        eventSink.endOfStream();
        eventChannel.setStreamHandler(null);
    

2.注册通信类：需要注意的是这里的FlutterActivity是io.flutter.embedding.android包下的

FlutterEventChannel 

package com.example.example;

import android.os.Bundle;

import com.example.FlutterEventChannel;

import io.flutter.embedding.android.FlutterActivity;

public class MainActivity extends FlutterActivity 

    @Override
    protected void onCreate(Bundle savedInstanceState) 
        super.onCreate(savedInstanceState);
        
        FlutterEventChannel eventChannel = FlutterEventChannel.getInstance();
        getFlutterEngine().getPlugins().add(eventChannel);
    

3.Flutter中注册并调用

void main() 
  runApp(MyApp());


class MyApp extends StatefulWidget 
  @override
  _MyAppState createState() => _MyAppState();


class _MyAppState extends State<MyApp> 

  var _eventChannel = EventChannel('event_channel_name');

  @override
  void initState() 
    super.initState();
    _eventChannel.receiveBroadcastStream().listen((event) 
      print("event: $event");
    );
  

  @override
  Widget build(BuildContext context) 
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Plugin example app'),
        ),
      ),
    );