Flutter 与原生交互有三种方法：

BasicMessageChannel运用

MethodChannel运用

EventChannel 是原生向Flutter传递数据流的通道，属于单向传输，只能由原生端调用，Flutter端是接收信息，常见的有网络改变监听，屏幕横竖屏切换，位置切换，电池电量，长途通知等事情。

下面结合iOS端代码来描绘下运用方法

Flutter端代码

final eventChannel = const EventChannel('test_event_channel');

界说channel

Future<void> setEventChannel() async {
  _streamSubscription = eventChannel.receiveBroadcastStream().listen((event) {
    print('Flutter收到了原生端的事情：$event');
  }, onError: (error) {
    print(error);
  }, onDone: () {
    print('done');
  }, cancelOnError: true);
}

组件初始化中设置回调

  • 闭包第一个回调为onData，参数event为泛型，表示原生端回来的信息内容
  • onError: 报错会履行
/// Otherwise it is called with just the error object.
/// If [onError] is omitted, any errors on this stream are considered unhandled,
/// and will be passed to the current [Zone]'s error handler.
/// By default unhandled async errors are treated
/// as if they were uncaught top-level errors.
  • onDone: 时间完成会履行
/// If this stream closes and sends a done event, the [onDone] handler is
/// called. If [onDone] is `null`, nothing happens.
  • cancelOnError: 报错后是否撤销事情
/// If [cancelOnError] is `true`, the subscription is automatically canceled
/// when the first error event is delivered. The default is `false`.

iOS原生端

class EventChannelManager: NSObject {
  var channel: FlutterEventChannel
  var eventSink: FlutterEventSink?
  var count = 0
  var timer: Timer?
  init(messager: FlutterBinaryMessenger) {
    channel = FlutterEventChannel(name: "test_event_channel", binaryMessenger: messager)
  }
  func config() {
    channel.setStreamHandler(**self**)
  }
  func startTimer() {
   timer = Timer(timeInterval: TimeInterval(2), target: self, selector: #selectortriggerEventChannel), userInfo: nil, repeats: true)
    RunLoop.current.add(timer!, forMode: .common)
  }
  @objc func triggerEventChannel() {
    count += 1
    eventSink?("当时数值为：\(count)")
  }
}
extension EventChannelManager : FlutterStreamHandler {
  func onListen(withArguments arguments: Any?, eventSink events: @escaping FlutterEventSink) -> FlutterError? {
    self.eventSink = events
    startTimer()
    return nil
  }
  func onCancel(withArguments arguments: **Any**?) -> FlutterError? {
    return nil
  }
}

AppDelegate中调用：

let eventChannelManager = EventChannelManager(messager: messager)
eventChannelManager.config()

和其他两种通讯方法不同的是，EventChannel需要在原生端完成 FlutterStreamHandler协议，获取到 FlutterEventSink，用它来进行消息的发送

eventSink?("当时数值为：\(count)")

打印结果如下：

Flutter与原生通信之EventChannel