UGUI中EventSystem，EventTrigger响应事件介绍

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看到群里有小伙伴再问UI的事件监听，分享一下。

方式一：组件拖拽

添加EventTrigger组件，拖拽实例，添加事件的这种方式就省略不讲了，在实际运用中虽然方便简单但是不推荐使用。

方式二：实现事件接口

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.EventSystems;

public class InfoPanel: MonoBehaviour,IPointerEnterHandler,IPointerExitHandler,IPointerDownHandler,IPointerClickHandler{

    public void OnPointerEnter (PointerEventData eventData)
    {
        Debug.Log ("enter");
        //鼠标进入当前实例范围，就触发
        Debug.Log (eventData.pointerEnter.name);
    }

    public void OnPointerExit(PointerEventData eventData){
        Debug.Log ("exit");
    }
    //按下就触发
    public void OnPointerDown(PointerEventData eventData){
        Debug.Log ("down");
        //Debug.Log (eventData.pointerPress.name); eventData.pointerPress.name该值只能写一个、不能重复写
    }

    //鼠标点击完成（按下，抬起）触发 ，如果按下的时候在别的地方抬起，则不会触发
    public void OnPointerClick(PointerEventData eventData){
        Debug.Log ("click");
    }
}

方式三：代码添加事件

  public Image image;
    public Image image1;
    // Use this for initialization
    void Start()
    {
        AddEventTriggerEvent(image, EventTriggerType.PointerDown, (o) => { Debug.Log("PointerDown"); });
        AddEventTriggerEvent(image1, EventTriggerType.PointerClick, (o) => { Debug.Log("PointerClick"); });

    }
    /// 

    /// 为EventTrigger添加事件及事件监听。
    /// 
    /// 带有或需要添加EventTrigger的对象
    /// 要添加的事件的类型
    /// 事件的触发回调
    private void AddEventTriggerEvent(Component obj, EventTriggerType eventType, UnityAction callback)
    {
        EventTrigger.Entry entry = null;
        EventTrigger trigger = obj.GetComponent();

        if (trigger != null) // 已有EventTrigger
        {
            // 查找是否已经存在要注册的事件
            foreach (EventTrigger.Entry existingEntry in trigger.triggers)
            {
                if (existingEntry.eventID == eventType)
                {
                    entry = existingEntry;
                    break;
                }
            }
        }
        else 
        {
            trigger = obj.gameObject.AddComponent();
        }
        // 如果这个事件不存在，就创建新的实例
        if (entry == null)
        {
            entry = new EventTrigger.Entry();
            entry.eventID = eventType;
        }
        // 添加触发回调并注册事件
        entry.callback.AddListener(callback);
        trigger.triggers.Add(entry);
    }

 方式四：继承EventTrigger，重写需要的逻辑

public class UGUIEventListener : EventTrigger
{
    public delegate void VoidDelegate(GameObject go);
    public VoidDelegate onClick;
    public VoidDelegate onDown;
    public VoidDelegate onEnter;
    public VoidDelegate onExit;
    public VoidDelegate onUp;
    public VoidDelegate onSelect;
    public VoidDelegate onUpdateSelect;
    public VoidDelegate onLongPress;                    //长按按键

    public float interval = 1f;                         //长按按键判断间隔
    public float invokeInterval = 0.2f;                 //长按状态方法调用间隔
    private bool isPointDown = false;
    private float lastInvokeTime;                       //鼠标点击下的时间
    private float timer;
    static public UGUIEventListener Get(GameObject go)
    {
        UGUIEventListener listener = go.GetComponent();
        if (listener == null) listener = go.AddComponent();
        return listener;
    }
    public override void OnPointerClick(PointerEventData eventData)
    {
        if (onClick != null) onClick(gameObject);
    }

    public override void OnPointerDown(PointerEventData eventData)
    {
        isPointDown = true;
        lastInvokeTime = Time.time;
        if (onDown != null) onDown(gameObject);
    }
    public override void OnPointerEnter(PointerEventData eventData)
    {
        if (onEnter != null) onEnter(gameObject);
    }
    public override void OnPointerExit(PointerEventData eventData)
    {
        isPointDown = false;                            //鼠标移出按钮时推出长按状态
        if (onExit != null) onExit(gameObject);
    }
    public override void OnPointerUp(PointerEventData eventData)
    {
        isPointDown = false;
        if (onUp != null) onUp(gameObject);
    }
    public override void OnSelect(BaseEventData eventData)
    {
        if (onSelect != null) onSelect(gameObject);
    }
    public override void OnUpdateSelected(BaseEventData eventData)
    {
        if (onUpdateSelect != null) onUpdateSelect(gameObject);
    }
    private void Update()
    {
        if (isPointDown)
        {
            if (Time.time - lastInvokeTime > interval)
            {
                timer += Time.deltaTime;
                if (timer > invokeInterval)
                {
                    onLongPress.Invoke(gameObject);
                    timer = 0;
                }
            }
        }
    }

 

  public  GameObject image;

    // Use this for initialization
    private void Awake()
    {
        UGUIEventListener.Get(image).onLongPress = OnLongPress;
        UGUIEventListener.Get(image).onClick = OnClick;
        UGUIEventListener.Get(image).onDown = OnDown;
        UGUIEventListener.Get(image).onUp = OnUp;
        UGUIEventListener.Get(image).onEnter = OnEnter;
        UGUIEventListener.Get(image).onExit = OnExit;
    }

    private void OnExit(GameObject go)
    {
        Debug.Log("OnExit");
    }

    private void OnEnter(GameObject go)
    {
        Debug.Log("OnEnter");
    }

    private void OnUp(GameObject go)
    {
        Debug.Log("OnUp");
    }

    private void OnDown(GameObject go)
    {
        Debug.Log("OnDown");
    }

    private void OnClick(GameObject go)
    {
        Debug.Log("OnClick");
    }

    public void OnLongPress(GameObject go)
    {
        Debug.Log("OnLongPress");
    }

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