關於Unity中UGUI圖片Image實現仿視頻播放窗口的四角縮放功能

應用方法：將下面腳本掛載在需要實現四角縮放功能的UI圖片上即可.

自定義拖拽精度（與邊界距離多少內觸發）m_validityWidth.

 

/*************************************************
 * 項目名稱：UGUI通用
 * 腳本創建人：魔卡
 * 腳本創建時間：2017.12.14
 * 腳本功能：UI圖片仿視頻窗口縮放
 * ***********************************************/
using UnityEngine;
using System.Collections;
using System.Diagnostics;
using UnityEngine.EventSystems;
using Debug = UnityEngine.Debug;

//圖片仿視頻窗口縮放類
public class UIDragResizeByMocha : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler
{
    [Header( "有效檢測的邊緣寬度")]
    public float m_validityWidth = 10f;

    //存儲操作的拖拽方向(默認為無操作)
    private DragDirection m_direction = DragDirection.None;

    //1.上方  //5.左上角
    //2.下方  //6.左下角
    //3.左方  //7.右上角
    //4.右方  //8.右下角

    //存儲當前操作圖片位置
    private Vector3 tTargetPos;
    //存儲鼠標位置
    private Vector3 tMousePos;
    //存儲當前圖片寬度
    private float tWidth;
    //存儲當前圖片高度
    private float tHeight;

    //存儲不動點位置坐標
    //解釋一下：當我們拖動每個邊界時至少有一個點時應該不動的，我們就以該點為基准點，當拖動單面有兩點不動時我們取兩點的中間點為基准點
    private Vector3 m_basePoint;

    /// <summary>
    /// 拖拽時刷新數據
    /// </summary>
    /// <param name="eventData"></param>
    void DoRefresh(PointerEventData eventData)
    {
        //刷新鼠標位置
        tMousePos = eventData.position;
        //刷新圖片位置
        tTargetPos = transform.position;
        //刷新圖片寬度
        tWidth = GetComponent<RectTransform>().sizeDelta.x;
        //刷新圖片高度
        tHeight = GetComponent<RectTransform>().sizeDelta.y;
    }

    //拖動開始觸發
    public void OnBeginDrag(PointerEventData eventData)
    {
        //刷新數據方法
        DoRefresh(eventData);
       
    }
    //拖動進行中觸發
    public void OnDrag(PointerEventData eventData)
    {
        //刷新數據方法
        DoRefresh(eventData);

        #region 判定拖動方向
        //如果鼠標位置離左側邊界的限定距離內，設置對應的方向
        if (tMousePos.x < (tTargetPos.x - tWidth/2.0f + m_validityWidth))
        {
            m_direction = DragDirection.Left;
            //上
            if (tMousePos.y > (tTargetPos.y + tHeight/2.0f - m_validityWidth))
            {
                m_direction = DragDirection.LeftUp;
            }
                //下
            else if ((tMousePos.y < (tTargetPos.y - tHeight / 2.0f + m_validityWidth)))
            {
                m_direction = DragDirection.LeftDown;
            }
           
        }
        //如果鼠標位置離右側邊界的限定距離內
        else if(tMousePos.x > (tTargetPos.x + tWidth/2.0f - m_validityWidth))
        {
            m_direction = DragDirection.Right;
            //上
            if (tMousePos.y > (tTargetPos.y + tHeight / 2.0f - m_validityWidth))
            {
                m_direction = DragDirection.RightUp;
            }
            //下
            else if ((tMousePos.y < (tTargetPos.y - tHeight / 2.0f + m_validityWidth)))
            {
                m_direction = DragDirection.RightDown;
            }
        }
        //如果鼠標位置離上側邊界的限定距離內
        else if (tMousePos.y > (tTargetPos.y + tHeight / 2.0f - m_validityWidth))
        {
            m_direction = DragDirection.Up;
            //左
            if (tMousePos.x < (tTargetPos.x - tWidth/2.0f + m_validityWidth))
            {
                m_direction = DragDirection.LeftUp;
            }
            //右
            else if (tMousePos.x > (tTargetPos.x + tWidth/2.0f - m_validityWidth))
            {
                m_direction = DragDirection.RightUp;
            }
        }
        //如果鼠標位置離下側邊界的限定距離內
        else if ((tMousePos.y < (tTargetPos.y - tHeight/2.0f + m_validityWidth)))
        {
            m_direction = DragDirection.Down;
            //左
            if (tMousePos.x < (tTargetPos.x - tWidth/2.0f + m_validityWidth))
            {
                m_direction = DragDirection.LeftDown;
            }
            //右
            else if (tMousePos.x > (tTargetPos.x + tWidth/2.0f - m_validityWidth))
            {
                m_direction = DragDirection.RightDown;
            }
        }
        else
        {
            m_direction = DragDirection.None;
        }


    #endregion

        //根據當前判定的方向做出相應的仿視頻窗口縮放
        switch (m_direction)
        {
            case DragDirection.Left :
                DoLeft();
                break;
            case DragDirection.Right :
                DoRight();
                break;
            case DragDirection.Up:
                DoUp();
                break;
            case DragDirection.Down :
                DoDown();
                break;
            case DragDirection.LeftUp :
                DoLeftUp();
                break;
            case DragDirection.LeftDown :
                DoLeftDown();
                break;
            case DragDirection.RightUp:
                DoRightUp();
                break;
            case DragDirection.RightDown :
                DoRightDown();
                break;
            default :
                Debug.Assert(false);
                break;
        }
            
    }

    #region 各個方向對應的調整方法
    /// <summary>
    /// 左拖動改變圖片橫向大小
    /// </summary>
    void DoLeft()
    {
        //設定基准點坐標
        m_basePoint = tTargetPos + new Vector3(tWidth/2.0f,0,0);
        //設定圖片寬度
        float ttWidth = Mathf.Abs(m_basePoint.x - tMousePos.x);
        GetComponent<RectTransform>().sizeDelta = new Vector2(ttWidth, tHeight);
        //設置圖片位置
        transform.position = m_basePoint - new Vector3(ttWidth/2.0f, 0, 0);
    }
    /// <summary>
    /// 右拖動改變圖片橫向大小
    /// </summary>
    void DoRight()
    {
        //設定基准點坐標
        m_basePoint = tTargetPos - new Vector3(tWidth / 2.0f, 0, 0);
        //設定圖片寬度
        float ttWidth = Mathf.Abs(m_basePoint.x - tMousePos.x);
        GetComponent<RectTransform>().sizeDelta = new Vector2(ttWidth, tHeight);
        //設置圖片位置
        transform.position = m_basePoint + new Vector3(ttWidth / 2.0f, 0, 0);
    }
    /// <summary>
    /// 上拖動改變圖片橫向大小
    /// </summary>
    void DoUp()
    {
        //設定基准點坐標
        m_basePoint = tTargetPos - new Vector3(0, tHeight /2.0f, 0);
        //設定圖片高度
        float ttHeight = Mathf.Abs(m_basePoint.y - tMousePos.y);
        GetComponent<RectTransform>().sizeDelta = new Vector2(tWidth, ttHeight);
        //設置圖片位置
        transform.position = m_basePoint + new Vector3(0, ttHeight/2.0f, 0);
    }
    /// <summary>
    /// 下拖動改變圖片橫向大小
    /// </summary>
    void DoDown()
    {
        //設定基准點坐標
        m_basePoint = tTargetPos + new Vector3(0, tHeight / 2.0f, 0);
        //設定圖片高度
        float ttHeight = Mathf.Abs(m_basePoint.y - tMousePos.y);
        GetComponent<RectTransform>().sizeDelta = new Vector2(tWidth, ttHeight);
        //設置圖片位置
        transform.position = m_basePoint - new Vector3(0, ttHeight / 2.0f, 0);
    }
    /// <summary>
    /// 左上拖動改變圖片橫向大小
    /// </summary>
    void DoLeftUp()
    {
        //設定基准點坐標
        m_basePoint = tTargetPos + new Vector3(tWidth / 2.0f, -tHeight /2.0f, 0);
        //設定圖片寬度
        float ttWidth = Mathf.Abs(m_basePoint.x - tMousePos.x);
        //設定圖片高度
        float ttHeight = Mathf.Abs(m_basePoint.y - tMousePos.y);
        GetComponent<RectTransform>().sizeDelta = new Vector2(ttWidth, ttHeight);
        //設置圖片位置
        transform.position = m_basePoint + new Vector3(-ttWidth / 2.0f, ttHeight / 2.0f, 0);
    }
    /// <summary>
    /// 左下拖動改變圖片橫向大小
    /// </summary>
    void DoLeftDown()
    {
        //設定基准點坐標
        m_basePoint = tTargetPos + new Vector3(tWidth / 2.0f, tHeight / 2.0f, 0);
        //設定圖片寬度
        float ttWidth = Mathf.Abs(m_basePoint.x - tMousePos.x);
        //設定圖片高度
        float ttHeight = Mathf.Abs(m_basePoint.y - tMousePos.y);
        GetComponent<RectTransform>().sizeDelta = new Vector2(ttWidth, ttHeight);
        //設置圖片位置
        transform.position = m_basePoint + new Vector3(-ttWidth / 2.0f, -ttHeight / 2.0f, 0);
    }
    /// <summary>
    /// 右上拖動改變圖片橫向大小
    /// </summary>
    void DoRightUp()
    {
        //設定基准點坐標
        m_basePoint = tTargetPos + new Vector3(-tWidth / 2.0f, -tHeight / 2.0f, 0);
        //設定圖片寬度
        float ttWidth = Mathf.Abs(m_basePoint.x - tMousePos.x);
        //設定圖片高度
        float ttHeight = Mathf.Abs(m_basePoint.y - tMousePos.y);
        GetComponent<RectTransform>().sizeDelta = new Vector2(ttWidth, ttHeight);
        //設置圖片位置
        transform.position = m_basePoint + new Vector3(ttWidth / 2.0f, ttHeight / 2.0f, 0);
    }
    /// <summary>
    /// 右下拖動改變圖片橫向大小
    /// </summary>
    void DoRightDown()
    {
        //設定基准點坐標
        m_basePoint = tTargetPos + new Vector3(-tWidth / 2.0f, tHeight / 2.0f, 0);
        //設定圖片寬度
        float ttWidth = Mathf.Abs(m_basePoint.x - tMousePos.x);
        //設定圖片高度
        float ttHeight = Mathf.Abs(m_basePoint.y - tMousePos.y);
        GetComponent<RectTransform>().sizeDelta = new Vector2(ttWidth, ttHeight);
        //設置圖片位置
        transform.position = m_basePoint + new Vector3(ttWidth / 2.0f, -ttHeight / 2.0f, 0);
    }
    #endregion 
    
    //拖動結束觸發
    public void OnEndDrag(PointerEventData eventData)
    {
        //重置拖動方向
        m_direction = DragDirection.None;
    }

}

/// <summary>
/// 拖拽方向枚舉
/// </summary>
public enum DragDirection
{
    None,       //無
    Up,         //上
    Down,       //下
    Left,       //左
    Right,      //右
    LeftUp,     //左上
    RightUp,    //右上
    LeftDown,   //左下
    RightDown   //右下
}