UGUI用代码添加EventTrigger的监听事件

手动添加EventTrigger的事件固然方便，但是不利于以后的修改，所以用代码添加是很有必要的。

起初使用的时候是参考了各家博主的代码，都大致相似，就直接拿来。但是当我要在一个EventTrigger下添加多个事件的时候，代码就冗余了，干脆封成一个方法，用起来方便，主要是不用费心思给那些临时变量起名字了。

代码如下：

    /// <summary>
    /// 添加EventTrigger的监听事件
    /// </summary>
    /// <param name="obj">添加监听的对象</param>
    /// <param name="eventID">添加的监听类型</param>
    /// <param name="action">触发方法</param>
    private void AddTriggersListener(GameObject obj, EventTriggerType eventID, UnityAction<BaseEventData> action)
    {
        EventTrigger trigger = obj.GetComponent<EventTrigger>();
        if (trigger == null)
        {
            trigger = obj.AddComponent<EventTrigger>();
        }

        if (trigger.triggers.Count == 0)
        {
            trigger.triggers = new List<EventTrigger.Entry>();
        }
        
        UnityAction<BaseEventData> callback = new UnityAction<BaseEventData>(action);
        EventTrigger.Entry entry = new EventTrigger.Entry();
        entry.eventID = eventID;
        entry.callback.AddListener(callback);
        trigger.triggers.Add(entry);
    }

使用示例：

//播放进度条EventTrigger监听
AddTriggersListener(sliderProgressBar.gameObject, EventTriggerType.PointerEnter, OnVideoPointerEnter);
AddTriggersListener(sliderProgressBar.gameObject, EventTriggerType.PointerExit, OnVideoPointerExit);
AddTriggersListener(sliderProgressBar.gameObject, EventTriggerType.PointerClick, OnVideoPointerClick);
AddTriggersListener(sliderProgressBar.gameObject, EventTriggerType.BeginDrag, OnVideoBeginDrag);
AddTriggersListener(sliderProgressBar.gameObject, EventTriggerType.EndDrag, OnVideoEndDrag);