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UI中的事件系统EventSystem

作者:互联网

一.EventSystem简介

  用于处理事件的分发和相应的系统,创建画布的同时会创建事件系统

 

 

 二.UGUI实现事件系统的3种方式

1.使用组件eventTrigger(不推荐),拖动赋值

 

2.代码添加enentTrigger组件,添加监听的方式

    private int _index;
    // Start is called before the first frame update
    void Start()
    {
        //添加trigger组件
        EventTrigger trigger = gameObject.AddComponent<EventTrigger>();
        //初始化一个事件列表
        trigger.triggers = new List<EventTrigger.Entry>();

        //定义绑定类型
        EventTrigger.Entry entry = new EventTrigger.Entry();
        entry.eventID = EventTriggerType.PointerClick;
        //添加事件监听方法
        entry.callback = new EventTrigger.TriggerEvent();
        entry.callback.AddListener((data) => ChangeColor());    //添加的方法必须带有基础数据参数data,目前data为空

        //将entry添加到trigger上去
        trigger.triggers.Add(entry);
    }

    //供注册使用的方法
    public void ChangeColor()
    {
        if(_index == 0)
        {
            GetComponent<Image>().color = Color.blue;
        }
        else
        {
            GetComponent<Image>().color = Color.red;
        }
        _index = _index == 0 ? 1 : 0;
    }

可以看到,Entry和TriggerEvent都是EventTrigger组件中的内部类,对应着绑定事件的类型和监听方法,Entry类中含有TriggerEvent类型的变量名称是callback。在添加好事件的类型和回调方法后将entry添加到EventTrigger的事件列表triggers上去。下面是源码中EventTrigger的代码:

namespace UnityEngine.EventSystems
{
    [AddComponentMenu("Event/Event Trigger")]
    public class EventTrigger : MonoBehaviour, IPointerEnterHandler, IEventSystemHandler, IPointerExitHandler, IPointerDownHandler, IPointerUpHandler, IPointerClickHandler, IInitializePotentialDragHandler, IBeginDragHandler, IDragHandler, IEndDragHandler, IDropHandler, IScrollHandler, IUpdateSelectedHandler, ISelectHandler, IDeselectHandler, IMoveHandler, ISubmitHandler, ICancelHandler
    {
        protected EventTrigger();

        public List<Entry> triggers { get; set; }
        [EditorBrowsable(EditorBrowsableState.Never)]
        [Obsolete("Please use triggers instead (UnityUpgradable) -> triggers", true)]
        public List<Entry> delegates { get; set; }

        public virtual void OnBeginDrag(PointerEventData eventData);
        public virtual void OnCancel(BaseEventData eventData);
        public virtual void OnDeselect(BaseEventData eventData);
        public virtual void OnDrag(PointerEventData eventData);
        public virtual void OnDrop(PointerEventData eventData);
        public virtual void OnEndDrag(PointerEventData eventData);
        public virtual void OnInitializePotentialDrag(PointerEventData eventData);
        public virtual void OnMove(AxisEventData eventData);
        public virtual void OnPointerClick(PointerEventData eventData);
        public virtual void OnPointerDown(PointerEventData eventData);
        public virtual void OnPointerEnter(PointerEventData eventData);
        public virtual void OnPointerExit(PointerEventData eventData);
        public virtual void OnPointerUp(PointerEventData eventData);
        public virtual void OnScroll(PointerEventData eventData);
        public virtual void OnSelect(BaseEventData eventData);
        public virtual void OnSubmit(BaseEventData eventData);
        public virtual void OnUpdateSelected(BaseEventData eventData);

        public class TriggerEvent : UnityEvent<BaseEventData>
        {
            public TriggerEvent();
        }
        public class Entry
        {
            public EventTriggerType eventID;
            public TriggerEvent callback;

            public Entry();
        }
    }
}

从源码中也可以发现,EventTrigger本质上是通过接口的方式实现的事件,可以理解为这个类是对事件接口实现事件的方式的封装类。

 

3.使用接口

观察上方的EventTrigger的源码,可以发现实现了非常多的接口,这些接口就是事件接口:

public class EventTrigger : MonoBehaviour, IPointerEnterHandler, IEventSystemHandler, IPointerExitHandler, IPointerDownHandler, IPointerUpHandler, IPointerClickHandler, IInitializePotentialDragHandler, IBeginDragHandler, IDragHandler, IEndDragHandler, IDropHandler, IScrollHandler, IUpdateSelectedHandler, ISelectHandler, IDeselectHandler, IMoveHandler, ISubmitHandler, ICancelHandler

这些接口的方法的实现:

 

 

 下面我们分类介绍这些接口

拖动事件的接口:(值得注意的是,没有IDragHandler接口其他3个接口的实现方法不会被执行,因此必须继承IDragHandler接口)

IInitializePotentialDragHandler:初始化拖动事件,初始化时执行一次

IBeginDragHandler:开始拖动时执行一次

IDragHandler:拖动的过程中不断执行

IEndDragHandler:结束拖动时执行一次

放下事件的接口:(同样的,要想IDropHandler接口的方法被执行,必须同时实现IDragHandler)

IDropHandler:在物体拖动后被放下时执行一次

鼠标指针事件的接口:(一次鼠标点击,可以触发down、up、click3个事件,事件执行顺序也是down、up、click)

IPointerClickHandler:物体接受点击时执行一次

IPointerEnterHandler:鼠标指针进入物体范围时执行一次

IPointerExitHandler:鼠标指针移除物体范围时执行一次

IPointerDownHandler:鼠标按下时执行一次

IPointerUpHandler:鼠标抬起时执行一次

选中事件的接口:

ISelectHandler:物体被选中时执行一次

IUpdateSelectedHandler:物体是被选中状态不断执行

IDeselectHandler:物体结束选中状态时执行一次

按键事件的接口:

IScrollHandler:鼠标的滚轮滚动时执行

ISubmitHandler:提交键按下时执行

ICancelHandler:取消键按下后执行

IMoveHandler:方向键等按下后执行

 

三.接口的方法参数类型PointerEventData

下面是这个类的源码:

public class PointerEventData : BaseEventData
    {
        public List<GameObject> hovered;

        public PointerEventData(EventSystem eventSystem);

        public GameObject pointerPress { get; set; }
        public Camera pressEventCamera { get; }
        public Camera enterEventCamera { get; }
        public InputButton button { get; set; }
        public bool dragging { get; set; }
        public bool useDragThreshold { get; set; }
        public Vector2 scrollDelta { get; set; }
        public int clickCount { get; set; }
        public float clickTime { get; set; }
        [Obsolete("Use either pointerCurrentRaycast.worldNormal or pointerPressRaycast.worldNormal")]
        public Vector3 worldNormal { get; set; }
        [Obsolete("Use either pointerCurrentRaycast.worldPosition or pointerPressRaycast.worldPosition")]
        public Vector3 worldPosition { get; set; }
        public Vector2 pressPosition { get; set; }
        public Vector2 delta { get; set; }
        public Vector2 position { get; set; }
        public int pointerId { get; set; }
        public bool eligibleForClick { get; set; }
        public RaycastResult pointerPressRaycast { get; set; }
        public RaycastResult pointerCurrentRaycast { get; set; }
        public GameObject pointerDrag { get; set; }
        public GameObject rawPointerPress { get; set; }
        public GameObject lastPress { get; }
        public GameObject pointerEnter { get; set; }

        public bool IsPointerMoving();
        public bool IsScrolling();
        public override string ToString();

        public enum InputButton
        {
            Left = 0,
            Right = 1,
            Middle = 2
        }
        public enum FramePressState
        {
            Pressed = 0,
            Released = 1,
            PressedAndReleased = 2,
            NotChanged = 3
        }
    }

可以看到,这个类是用于记录事件信息如拖动距离、是否拖动、输入的键信息等的对象模板。所有的事件接口的方法都有且仅有一个PointerEventData类的参数。

标签:set,get,EventSystem,void,virtual,UI,事件,eventData,public
来源: https://www.cnblogs.com/movin2333/p/14311021.html