unity(二) —— 实现拖拽

使用条件：
1.场景中要有EventSystem
2.脚本引用命名空间using UnityEngine.EventSystems;
3.脚本继承自MonoBehaviour
4.脚本要实现接口IBeginDragHandler,IDragHandler
5.仅对UGUI有效，ui的image组件的RaycastTarget必须勾选上

using UnityEngine;
using UnityEngine.EventSystems;
public class DragDetails : MonoBehaviour, IBeginDragHandler, IDragHandler
{

    private Vector3 offset;
    public void OnBeginDrag(PointerEventData eventData)
    {
        //开始拖拽的时候记录偏移量
        Vector3 v3;
        RectTransformUtility.ScreenPointToWorldPointInRectangle(GetComponent<RectTransform>(),
            eventData.position, eventData.enterEventCamera, out v3);
        offset = transform.position - v3;

    }

    public void OnDrag(PointerEventData eventData)
    {
        transform.position = Input.mousePosition + offset;
    }

    //public void OnEndDrag(PointerEventData eventData)
    //{
    //    throw new System.NotImplementedException();
    //}
}