UGUI中的接口事件的实现

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

//给空间添加监听事件要实现的一些接口
public class MyDragEvent : MonoBehaviour, IPointerDownHandler, IDragHandler, IPointerUpHandler,
IEndDragHandler, IPointerEnterHandler, IPointerExitHandler
{

public RectTransform canvas; //得到canvas的ugui坐标
private RectTransform imgRect; //得到图片的ugui坐标
Vector2 offset = new Vector3(); //用来得到鼠标和图片的差值
Vector3 imgReduceScale = new Vector3(0.7f, 0.7f, 1); //设置图片缩放
Vector3 imgNormalScale = new Vector3(1, 1, 1); //正常大小

// Use this for initialization
void Start()
{
imgRect = GetComponent<RectTransform>();

}

//当鼠标按下时调用 接口对应 IPointerDownHandler
public void OnPointerDown(PointerEventData eventData)
{
Vector2 mouseDown = eventData.position; //记录鼠标按下时的屏幕坐标
Vector2 mouseUguiPos = new Vector2(); //定义一个接收返回的ugui坐标
//RectTransformUtility.ScreenPointToLocalPointInRectangle()：把屏幕坐标转化成ugui坐标
//canvas：坐标要转换到哪一个物体上，这里img父类是Canvas，我们就用Canvas
//eventData.enterEventCamera：这个事件是由哪个摄像机执行的
//out mouseUguiPos：返回转换后的ugui坐标
//isRect：方法返回一个bool值，判断鼠标按下的点是否在要转换的物体上
bool isRect = RectTransformUtility.ScreenPointToLocalPointInRectangle(canvas, mouseDown, eventData.enterEventCamera, out mouseUguiPos);
if (isRect) //如果在
{
//计算图片中心和鼠标点的差值
offset = imgRect.anchoredPosition - mouseUguiPos;
}
}

//当鼠标拖动时调用 对应接口 IDragHandler
public void OnDrag(PointerEventData eventData)
{
Vector2 mouseDrag = eventData.position; //当鼠标拖动时的屏幕坐标
Vector2 uguiPos = new Vector2(); //用来接收转换后的拖动坐标
//和上面类似
bool isRect = RectTransformUtility.ScreenPointToLocalPointInRectangle(canvas, mouseDrag, eventData.enterEventCamera, out uguiPos);

if (isRect)
{
//设置图片的ugui坐标与鼠标的ugui坐标保持不变
imgRect.anchoredPosition = offset + uguiPos;
}
}

//当鼠标抬起时调用 对应接口 IPointerUpHandler
public void OnPointerUp(PointerEventData eventData)
{
offset = Vector2.zero;
}

//当鼠标结束拖动时调用 对应接口 IEndDragHandler
public void OnEndDrag(PointerEventData eventData)
{
offset = Vector2.zero;
}

//当鼠标进入图片时调用 对应接口 IPointerEnterHandler
public void OnPointerEnter(PointerEventData eventData)
{
imgRect.localScale = imgReduceScale; //缩小图片
}

//当鼠标退出图片时调用 对应接口 IPointerExitHandler
public void OnPointerExit(PointerEventData eventData)
{
imgRect.localScale = imgNormalScale; //回复图片
}
}