get(recognizer) {
    if (recognizer instanceof Recognizer) {
      return recognizer;
    }

    let { recognizers } = this;
    for (let i = 0; i < recognizers.length; i++) {
      if (recognizers[i].options.event === recognizer) {
        return recognizers[i];
      }
    }
    return null;
  }
@private
get a recognizer by its event name.
@param {Recognizer|String} recognizer
@returns {Recognizer|Null}