UGUI中实现拖动UI

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

public class mapdrag : MonoBehaviour, IDragHandler, IEndDragHandler, IScrollHandler,IPointerDownHandler
{
    private RectTransform m_DraggingPlane;
    private GameObject m_DraggingIcon = null;
    private Vector3 temp;

    public void OnBeginDrag(PointerEventData eventData)
    {
    }
    public void OnDrag(PointerEventData eventData)
    {
        //Debug.Log("OnDrag" + eventData.ToString());
        if (eventData.pointerEnter != null && eventData.pointerEnter.transform as RectTransform != null)
        {
            m_DraggingPlane = eventData.pointerEnter.transform as RectTransform;
            print(m_DraggingPlane.name);
        }

       

        var rt = transform.GetComponent<RectTransform>();
        Vector3 GlobalVariableMousePos;
        if (RectTransformUtility.ScreenPointToWorldPointInRectangle(m_DraggingPlane, eventData.position, eventData.pressEventCamera, out GlobalVariableMousePos))
        {

            Vector3 pos = Camera.main.WorldToScreenPoint(GlobalVariableMousePos);
            
            //pos.y = rt.rect.height;// pos.y + 
            rt.position = GlobalVariableMousePos - temp;
        }        
    }

    public void OnEndDrag(PointerEventData eventData)  //结束拖动时调用
    {
        //Debug.Log("OnEndDrag" + eventData.ToString());
    }

    public void OnPointerDown(PointerEventData eventData)  //鼠标按下时候调用
    {
        
        if (eventData.pointerEnter != null && eventData.pointerEnter.transform as RectTransform != null)
        {
            m_DraggingPlane = eventData.pointerEnter.transform as RectTransform;
            print("OnPointerDown:"+m_DraggingPlane.gameObject.name);
        }
        else
            return;
        var rt = transform.GetComponent<RectTransform>();
        Vector3 GlobalVariableMousePos;
        if (RectTransformUtility.ScreenPointToWorldPointInRectangle(m_DraggingPlane, eventData.position, eventData.pressEventCamera, out GlobalVariableMousePos))
        {
            temp = GlobalVariableMousePos - transform.GetComponent<RectTransform>().position;
        }

    }

    public void OnScroll(PointerEventData eventData)
    {
        //Debug.Log("OnScroll" + eventData.scrollDelta.ToString());
        //float gunlunspeed = eventData.scrollDelta.y*0.1f;
        //transform.localScale += new Vector3(gunlunspeed, gunlunspeed, 0.0f); 
        //if (transform.localScale.x < 0.2f)
        //{
        //    transform.localScale = new Vector3(0.2f, 0.2f,  1.0f);
        //}
        //GameObject.Find("Main Camera").GetComponent<cameramain>().ischenged = true;
    }

}

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关键在这一行RectTransformUtility.ScreenPointToWorldPointInRectangle(m_DraggingPlane, eventData.position, eventData.pressEventCamera, out GlobalVariableMousePos)

 

eventData.position  ：鼠标的屏幕坐标

m_DraggingPlane： 将屏幕坐标转换成m_DraggingPlane所在平面的世界坐标上，并且只转换m_DraggingPlane区域里面的屏幕坐标

注意我的用词：m_DraggingPlane是在这个区域内的屏幕坐标

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FR:徐海涛（hunk Xu）