Android侧

class MainActivity :
        FlutterFragmentActivity(),
        EventChannel.StreamHandler {
    
      private var eventSink: EventChannel.EventSink? = null
    
       override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
            super.configureFlutterEngine(flutterEngine)
            startEventChannel(flutterEngine.dartExecutor.binaryMessenger)
        }
    
       private fun startEventChannel(messenger: BinaryMessenger) {
            EventChannel(messenger, "Channel").setStreamHandler(this)
        }
    
      override fun onWindowFocusChanged(hasFocus: Boolean) {
            super.onWindowFocusChanged(hasFocus)
            eventSink?.success(hasFocus)
        }
    
       override fun onListen(arguments: Any?, events: EventChannel.EventSink?) {
            eventSink = events
        }
    
        override fun onCancel(arguments: Any?) {
            eventSink = null
        }
    
    }

Flutter侧

final _eventChannel =
      const EventChannel('Channel');

  

    Future<void> getValue() async {
        try {
          _eventChannel
              .receiveBroadcastStream()
              .asyncMap((dynamic event) => event)
              .listen((event) {
            emit(state.copyWith(
              status: Status.success,
              hasFocus: event as bool,
            ));
          });
        } on PlatformException catch (e) {
          emit(state.copyWith(
            status: Status.failure,
            errorMessage: e.message ?? "Unknown error",
          ));
        }
      }