仿U3D回调方式的通用3D物体拖拽基类

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

public class Drag3DBase : MonoBehaviour,IDragHandler,IBeginDragHandler,IEndDragHandler {


    bool drag = false;
    float distance;
    Vector3 originPointPos;
    Vector3 originObjPos;

    public void OnBeginDrag(PointerEventData eventData)
    {
        if (eventData.rawPointerPress.transform == this.transform)
        {
            drag = true;
            distance = eventData.pointerPressRaycast.distance;
            originPointPos = GetWorldPos(eventData.position, distance);
            originObjPos = this.gameObject.transform.position;
            OnBeginDragHandle(eventData);
        }
    }
    public void OnDrag(PointerEventData eventData)
    {
        if (!drag)
            return;

        Vector3 tempPos = GetWorldPos(eventData.position, distance);
        Vector3 deltaPos = tempPos - originPointPos;
        this.transform.position = (originObjPos + deltaPos);
        OnDragHandle(eventData);

    }
    public void OnEndDrag(PointerEventData eventData)
    {
        if (!drag)
            return;

        drag = false;
        OnEndDragHandle(eventData);
    }
    protected Vector3 GetWorldPos(Vector2 mousePos, float distance)
    {
        Ray ray = Camera.main.ScreenPointToRay(mousePos);
        return ray.GetPoint(distance);
    }

    protected virtual void OnBeginDragHandle(PointerEventData eventData)
    {

    }
    protected virtual void OnDragHandle(PointerEventData eventData)
    {

    }
    protected virtual void OnEndDragHandle(PointerEventData eventData)
    {

    }
}