flutter的消息推送之后，在app上收到消息，怎么收到点击消息的回调？

flutter的消息推送之后，在app上收到消息，怎么收到点击消息的回调？

class UmengPushSdk {
  static MethodChannel _channel = const MethodChannel('u-push');

  static _Callbacks _callback = _Callbacks(_channel);

  ///设置token回调
  static void setTokenCallback(Callback callback) {
    _callback.tokenCallback = callback;
  }

  ///设置自定义消息回调
  static void setMessageCallback(Callback callback) {
    _callback.messageCallback = callback;
  }

  ///初始化推送
  static Future<void> register() async {
    return await _channel.invokeMethod(_METHOD_REGISTER);
  }

  ///获取推送id
  static Future<String> getRegisteredId() async {
    return await _channel.invokeMethod(_METHOD_DEVICE_TOKEN);
  }

  static Future<void> setPushEnable(bool enable) async {
    return await _channel.invokeMethod(_METHOD_PUSH_ENABLE, enable);
  }

  static Future<bool> setAlias(String alias, String type) async {
    return await _channel.invokeMethod(_METHOD_SET_ALIAS, {'alias': alias, 'type': type});
  }

  static Future<bool> addAlias(String alias, String type) async {
    return await _channel.invokeMethod(_METHOD_ADD_ALIAS, {'alias': alias, 'type': type});
  }

  static Future<bool> removeAlias(String alias, String type) async {
    return await _channel.invokeMethod(_METHOD_REMOVE_ALIAS, {'alias': alias, 'type': type});
  }

  static Future<bool> addTags(List<String> tags) async {
    return await _channel.invokeMethod(_METHOD_ADD_TAG, tags);
  }

  static Future<bool> removeTags(List<String> tags) async {
    return await _channel.invokeMethod(_METHOD_REMOVE_TAG, tags);
  }

  static Future<List<dynamic>> getTags() async {
    return await _channel.invokeMethod(_METHOD_GET_ALL_TAG);
  }
}