using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;
public class DragWindow : MonoBehaviour, IDragHandler, IBeginDragHandler, IEndDragHandler, IPointerClickHandler
{
    Vector3 offest;
    bool CanDrag = false;
    bool isFirstDrag = true;
    /// <summary>
    /// 是否忽略是否在UI上保持可拖动？
    /// </summary>
    [Header("是否忽略是否在UI上保持可拖动？")]
    public bool IgnoretheUI = false;
    //刚开始拖拽时第一下触发这个函数
    public void OnBeginDrag(PointerEventData eventData)
    {
        if (!IgnoretheUI)
            if (EventSystem.current.IsPointerOverGameObject()) return;
        if (RectTransformUtility.RectangleContainsScreenPoint(transform as RectTransform, Input.mousePosition))
        {
            //1、计算所有需要的数据 image本身的坐标 鼠标所在的位置相对于Canvas的本地坐标
            Vector2 localPos;

            RectTransformUtility.ScreenPointToLocalPointInRectangle(transform as RectTransform, Input.mousePosition, null, out localPos);
            //2、计算偏移量
            offest = vector2TpVector3(localPos);

            CanDrag = true;
        }
    }

    Vector3 vector2TpVector3(Vector2 vector2)
    {
        return new Vector3(vector2.x, vector2.y, 0);
    }
    public void OnDrag(PointerEventData eventData)
    {
        if (!IgnoretheUI)
            if (EventSystem.current.IsPointerOverGameObject()) return;
        if (CanDrag)
        {
            Vector2 localPosition;
            RectTransformUtility.ScreenPointToLocalPointInRectangle(transform.parent as RectTransform, Input.mousePosition, null, out localPosition);
            //transform.localPosition = localPosition;
            // offest = vector2TpVector3(localPosition);

            transform.localPosition = vector2TpVector3(localPosition) - offest;
        }
    }
    //停止拖拽
    public void OnEndDrag(PointerEventData eventData)
    {
        if (!IgnoretheUI)
            if (EventSystem.current.IsPointerOverGameObject()) return;
        CanDrag = false;
        if (isFirstDrag && transform.Find("tip"))
        {
            transform.Find("tip").gameObject.SetActive(false);
            isFirstDrag = false;
        }
    }

    public void OnPointerClick(PointerEventData eventData)
    {

    }
}