HK_LongZhiMeng/Assets/Scripts/DragObject.cs

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

public class DragObject : MonoBehaviour {

    public bool isDrag=true;
    private Vector3 realPosition;
    IEnumerator OnMouseDown()
    {
        if (isDrag)
        {
            Vector3 screenSpace = Camera.main.WorldToScreenPoint(transform.position);//三维物体坐标转屏幕坐标
                                                                                     //将鼠标屏幕坐标转为三维坐标，再算出物体位置与鼠标之间的距离
            Vector3 offset = transform.position - Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, screenSpace.z));
            while (Input.GetMouseButton(0))
            {
                Vector3 curScreenSpace = new Vector3(Input.mousePosition.x, Input.mousePosition.y, screenSpace.z);
                Vector3 curPosition = Camera.main.ScreenToWorldPoint(curScreenSpace) + offset;
                realPosition = new Vector3(curPosition.x, transform.position.y, curPosition.z);
                if (Input.GetKey(KeyCode.LeftControl))
                    realPosition = new Vector3(transform.position.x, curPosition.y, transform.position.z);

                if (!EventSystem.current.IsPointerOverGameObject())
                    transform.position = realPosition;
                yield return 0;//这个很重要，循环执行

            }
        }
        
    }

}