使用UGUI实现拖拽功能（拼图小游戏）

实现方式

1、引入UGUI自带的事件系统　　UnityEngine.EventSystems

2、为我们的类添加接口　　IBeginDragHandler, IDragHandler, IEndDragHandler

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

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


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


    void IDragHandler.OnDrag (PointerEventData eventData)
    {
        throw new System.NotImplementedException ();
    }


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

}

拼图游戏实例

1、准备一张拼图要用到的图片素材，并拖入Unity中

2、图片的TextureType选为Sprite(2D and UI)， 点击Apply

3、将SpriteMode改为Multiple，点击SpriteEditor，在弹出的窗口中点Slice，Type为Grid，我这张图片分辨率是500x500的，拆分为16份，所以我的PixelSize是125x125，最终结果如下图：

4、添加一个Panel作为背景，为Panel添加GridLayoutGroup组件，具体设置如下，添加脚本ImageCreater用于生成图片

5、为Panel添加一个Image作为我们拼图的格子的背景，名字改为Cell，在这个Cell上再添加一个Image作为图片的载体，并将它的Tag设置为Cell，为Image添加拖拽脚本DragOnPic，将Cell拖成预制体备用

6、新建一个GameManager类用于实现随机生成图片的功能

public class GameManager  {

    /// <summary>
    /// Randoms the array.
    /// </summary>
    static public void RandomArray(Sprite[] sprites)
    {
        for (int i = 0; i < sprites.Length; i++) {
            //随机抽取数字中的一个位置，并将这张图片与第i张图片交换.
            int index = Random.Range(i, sprites.Length);
            Sprite temp = sprites[i];
            sprites[i] = sprites[index];
            sprites[index] = temp;
        }
    }
}

7、在ImageCreater中写入生产图片的方法

using UnityEngine;
using System.Collections;
using UnityEngine.UI;

public class ImageCreater : MonoBehaviour {

    public static ImageCreater _instance;

    //存储裁剪好图片的数组.
    public Sprite[] sprites;

    //格子的预设体.
    public GameObject cellPrefab;

    void Start () {
        _instance = this;
        CreateImages();
    }
    
    private void CreateImages()
    {
        //将图片数组随机排列.
        GameManager.RandomArray(sprites);

        //生产图片.
        for (int i = 0; i < sprites.Length; i++) {
            //通过预设体生成图片.
            GameObject cell = (GameObject)Instantiate(cellPrefab);

            //设置cell的名字方便检测是否完成拼图.
            cell.name = i.ToString();

            //获取cell的子物体.
            Transform image = cell.transform.GetChild(0);

            //设置显示的图片.
            image.GetComponent<Image>().sprite = sprites[i];

            //设置子物体的名称，方便检测是否完成拼图.
            int tempIndex = sprites[i].name.LastIndexOf('_');
            image.name = sprites[i].name.Substring(tempIndex + 1);

            //将Cell设置为Panel的子物体.
            cell.transform.SetParent(this.transform);

            //初始化大小.
            cell.transform.localScale = Vector3.one;
        }
    }

}

8、到这里，拼图游戏已经基本成形，下面只需要实现每张图片的拖拽功能就OK了，下面是DragOnPic的代码

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

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

    //记录下自己的父物体.
    Transform myParent;

    //Panel，使拖拽是显示在最上方.
    Transform tempParent;

    CanvasGroup cg;
    RectTransform rt;

    //记录鼠标位置.
    Vector3 newPosition;

    void Awake()
    {
        //添加CanvasGroup组件用于在拖拽是忽略自己，从而检测到被交换的图片.
        cg = this.gameObject.AddComponent<CanvasGroup>();

        rt = this.GetComponent<RectTransform>();

        tempParent = GameObject.Find("Canvas").transform;
    }




    /// <summary>
    /// Raises the begin drag event.
    /// </summary>
    public void OnBeginDrag (PointerEventData eventData)
    {
        //拖拽开始时记下自己的父物体.
        myParent = transform.parent;

        //拖拽开始时禁用检测.
        cg.blocksRaycasts = false;

        this.transform.SetParent(tempParent);
    }
    
    /// <summary>
    /// Raises the drag event.
    /// </summary>
    void IDragHandler.OnDrag (PointerEventData eventData)
    {
        //推拽是图片跟随鼠标移动.
        RectTransformUtility.ScreenPointToWorldPointInRectangle(rt, Input.mousePosition, eventData.enterEventCamera, out newPosition);
        transform.position = newPosition;
    }
    
    /// <summary>
    /// Raises the end drag event.
    /// </summary>
    public void OnEndDrag (PointerEventData eventData)
    {
        //获取鼠标下面的物体.
        GameObject target = eventData.pointerEnter;

        //如果能检测到物体.
        if(target)
        {
            GameManager.SetParent(this.transform, target.transform, myParent);
        }
        else {
            this.transform.SetParent (myParent);
            this.transform.localPosition = Vector3.zero;
        }

        //拖拽结束时启用检测.
        cg.blocksRaycasts = true;

        //检测是否完成拼图.
        if(GameManager.CheckWin())
        {
            Debug.Log("Win!!!");
        }
        
    }
    
}

在GameManager中加入设置父物体的方法及检测是否完成拼图的方法：

 1　　  /// <summary>
    /// Sets the parent.
    /// </summary>
    static public void SetParent(Transform mine, Transform target, Transform oldParent)
    {
        //如果检测到图片，则交换父物体并重置位置.
        switch (target.tag)
        {
        case "Cell":
            mine.SetParent(target.parent);
            target.SetParent(oldParent);
            mine.localPosition = Vector3.zero;
            target.localPosition = Vector3.zero;
            break;
        default:
            mine.SetParent (oldParent);
            mine.localPosition = Vector3.zero;
            break;
        }
    }

    /// <summary>
    /// Checks is win.
    /// </summary>
    static public bool CheckWin()
    {
        for (int i = 0; i < ImageCreater._instance.transform.childCount; i++) {
            if(ImageCreater._instance.transform.GetChild(i).name != ImageCreater._instance.transform.GetChild (i).transform.GetChild(0).name)
            {
                return false;
            }
        } 
        return true;
    }

 到这里，拼图的基本功能就算是全部完成了

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