2021-01-07

using UnityEngine;

using UnityEngine.UI;

using UnityEngine.EventSystems;

using System.Collections;

 

public class DragPanel : MonoBehaviour, IDragHandler, IEndDragHandler, IBeginDragHandler

{

 

    private Vector2 originalLocalPointerPosition;

    private Vector3 originalPanelLocalPosition;

    public RectTransform panelRectTransform;

    public RectTransform restrictRectTransform;

 

    public float Damping;

    private Vector3 inertia;

    private float recordEndTime;

    private readonly float _refWidth = 768.0f;

    private readonly float _refHeight = 1334.0f;

    private readonly float _refRatio = 768.0f / 1334.0f;

    public void Awake()

    {

        inertia = Vector3.zero;

 

        restrictRectTransform.sizeDelta = (panelRectTransform.sizeDelta * 2 - new Vector2(_refWidth, Screen.height * (_refWidth / Screen.width)));

    }

 

    public void OnBeginDrag(PointerEventData data)

    {

        inertia = Vector3.zero;

        originalPanelLocalPosition = panelRectTransform.localPosition;

        RectTransformUtility.ScreenPointToLocalPointInRectangle(restrictRectTransform, data.position, data.pressEventCamera, out originalLocalPointerPosition);

    }

 

    public void OnDrag(PointerEventData data)

    {

        if (panelRectTransform == null || restrictRectTransform == null)

            return;

 

        Vector2 localPointerPosition;

        if (RectTransformUtility.ScreenPointToLocalPointInRectangle(restrictRectTransform, data.position, data.pressEventCamera, out localPointerPosition))

        {

            Vector3 offsetToOriginal = localPointerPosition - originalLocalPointerPosition;

            panelRectTransform.localPosition = originalPanelLocalPosition + offsetToOriginal;

        }

 

        ClampToWindow();

    }

 

    public void OnEndDrag(PointerEventData data)

    {

        inertia = data.delta;

        recordEndTime = Time.time;

    }

 

    public void Update()

    {

 

        if (inertia.magnitude > 0.1)

        {

            panelRectTransform.localPosition = panelRectTransform.localPosition + inertia;

            inertia = Vector3.Slerp(inertia, Vector3.zero, Mathf.Pow((Time.time - recordEndTime), 2) * Damping);

            ClampToWindow();

        }

    }

 

    // Clamp panel to area of parent

    void ClampToWindow()

    {

        Vector3 pos = panelRectTransform.localPosition;

 

        Vector3 minPosition = restrictRectTransform.rect.min - panelRectTransform.rect.min;

        Vector3 maxPosition = restrictRectTransform.rect.max - panelRectTransform.rect.max;

 

        pos.x = Mathf.Clamp(panelRectTransform.localPosition.x, minPosition.x, maxPosition.x);

        pos.y = Mathf.Clamp(panelRectTransform.localPosition.y, minPosition.y, maxPosition.y);

 

        panelRectTransform.localPosition = pos;

    }

 

    public void OpenFocs(Vector3 offset)

    {

        transform.position -= offset;

        ClampToWindow();

    }

}