首先，导入NGUI插件

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1、创建一个Sprite,创建一个空物体，也可以是图片，我这里创建的是空物体，
2、创建一个格子，保存成预制，拖三个sprite格子到场景中，
3、为第一个格子创建一个子对象作为背包的物品，把它设为预设体，并更改其名称。

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4、为格子添加Box Collider，为背包（Knaqpsack）添加Box Collider和
Drag Drop Item。

5、把物品的Drag Drop Item
删除，为物品添加脚本实现把物品拖放到任意格子里面都是居中的。脚本挂在要拖动的物品上（预制物体上）
//主角类
//Coder Joehn Chow
//2016/11/16
using UnityEngine;
using System.Collections;

public class KnapsackItem : UIDragDropItem //必须继承
{
protected override void OnDragDropRelease(GameObject surface)
{
base.OnDragDropRelease(surface);
if (surface.tag == "cell")
{
this.transform.parent = surface.transform;
this.transform.localPosition = Vector3.zero;
}
else if (surface.tag == "knapsack")
{
Transform t = surface.transform.parent;
surface.transform.parent = this.transform.parent;
surface.transform.localPosition = Vector3.zero;

        this.transform.parent = t;
        this.transform.localPosition = Vector3.zero;
    }
}

}

6、//脚本挂在空物体上
using UnityEngine;
using System.Collections;
public class Cells : MonoBehaviour
{
public GameObject[] items;//格子数组
public string[] names;//名字属性
public GameObject item;//即将往格子中添加预制物

void Update()
{
    if (Input.GetKeyDown(KeyCode.Q))
    {
        //Debug.Log("11");
        Pickup();//添加物体
    }
}

public void Pickup()
{
    int index = Random.Range(0,names.Length);
    string name = names[index];//获取其中一张图片的名字

    for (int i = 0; i < items.Length;i++ )
    {
        if (items[i].transform.childCount==0)//当前的格子里面没有物品
        {
            GameObject obj = NGUITools.AddChild(items[i],item);//添加物品到格子里
            obj.GetComponent<UISprite>().spriteName = name;
            obj.transform.localPosition = Vector3.zero;
            break;
        }
    }
}

if (Input.GetMouseButtonUp(0))
{
// 根据鼠标位置，从主相机发出射线，
Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
RaycastHit hit; // 用来获取从raycast函数中得到的信息反馈的结构
// 检测碰撞
if (Physics.Raycast(ray, out hit))
{
if (hit.collider.transform.name == "Plane") // 判断点击的物体是不是地面
{
GameObject cube = GameObject.CreatePrimitive(PrimitiveType.Cube);
cube.transform.position = hit.point+new Vector3(0,0.5f,0);
cube.GetComponent<MeshRenderer>().material.color = Random.ColorHSV();
cube.tag = "Cube";//设置tag
cube.AddComponent<MovePerfab>();
this.gameObject.GetComponent<UISprite>().enabled = false;
}

        }
    }

}

//拖动3D场景的对象的脚本
using UnityEngine;
using System.Collections;

public class MovePerfab : MonoBehaviour {

// Use this for initialization
void Start () {
    StartCoroutine("OnMouseDown");
}

// Update is called once per frame
void Update () {

}

IEnumerator OnMouseDown() {
    //物体世界坐标转为
    Vector3 worldtoscreenpos = Camera.main.WorldToScreenPoint(this.transform.position);

    Vector3 mousescreenspace = new Vector3(Input.mousePosition.x,Input.mousePosition.y,worldtoscreenpos.z);

    Vector3 offset = this.transform.position - Camera.main.ScreenToWorldPoint(mousescreenspace);

    while(Input.GetMouseButton(0)){
        mousescreenspace = new Vector3(Input.mousePosition.x, Input.mousePosition.y, worldtoscreenpos.z);

        this.transform.position = Camera.main.ScreenToWorldPoint(mousescreenspace) + offset;

        yield return new WaitForFixedUpdate();
    }
}

}

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另外参考:

Paste_Image.png

using UnityEngine;
using System.Collections;

public class a1104 : UIDragDropItem
{

public UISprite sprite;
public UILabel label;
private int count = 1;
public void AddCount(int number)
{
count += number;
label.text = count + "";
}

protected override void OnDragDropRelease(GameObject surface)
{
base.OnDragDropRelease(surface);

if (surface.tag=="cell")
{
this.transform.parent = surface.transform;
this.transform.localPosition = Vector3.zero;
}
else if (surface.tag == "knapsack")
{
Transform t = surface.transform.parent;
surface.transform.parent = this.transform.parent;
surface.transform.localPosition = Vector3.zero;

this.transform.parent = t;
this.transform.localPosition = Vector3.zero;
}
}
}

//脚本挂在背景图片上
using UnityEngine;
using System.Collections;

public class cells : MonoBehaviour
{
public GameObject[] cell;
public string[] equipmentsName;
public GameObject item;
void Update()
{
if(Input.GetKeyDown(KeyCode.Q))
{
Pickup();
}
}
public void Pickup()
{
int index = Random.Range(0, equipmentsName.Length);
string name = equipmentsName[index];
bool isFind = false;
for (int i = 0; i < cell.Length; i++)
{
if (cell[i].transform.childCount > 0)//判断当前格子有没有物品
{
//如果有的话
a1104 item = cell[i].GetComponentInChildren<a1104>();
//判断当前游戏物品的名字跟我们捡到的游戏物体名字是否一样
if (item.sprite.spriteName == name)
等价于//if (item.transform.GetComponent<UISprite>().spriteName == name)
{
isFind = true;
item.AddCount(1);
break;
}
}
}

if (isFind==false)
{
for (int i = 0; i < cell.Length; i++)
{
if (cell[i].transform.childCount == 0)
{
//当前位置没有物品
//添加我们新捡起的物品
GameObject go = NGUITools.AddChild(cell[i], item);
go.GetComponent<UISprite>().spriteName = name;
go.transform.localPosition = Vector3.zero;
break;
}
}
}

}
}