public static EventDispatcher GetInstance()
 {
     if (instance == null)
         instance = new EventDispatcher();
     return instance;
 }
 /// <summary>
 /// unregister the target event message.
 /// </summary>
 public void UnRegisterEvent()
 {
     EventDispatcher.GetInstance().MainEventManager.RemoveEventListener <string>(EventSystemDefine.EventTestUserInput, this.OnUserInput);
 }