onTask(id, eventName, func) {
    const handler = result => {
      if (result.id == id) {
        this.event.removeListener(eventName, handler);
        // this.removeTaskObj(eventName, result);
        func(result);
      }
    };

    this.event.on(eventName, handler);
  }
Listen to production task events
@param {string} id - a task id
@param {strint} eventName - task name
@param {function} func - task event handler
@public