一. 节点参考：

拖动的脚本放在子Panel上（需要一个父Panel）
修改大小脚本放在Panel下的Resize节点上

二. 拖动Panel

1. 注意点：

• 此处的RectTransform.Rect.min为矩形左上角点相对pivot即中心点的位置，max为右下角，详细参考：https://docs.unity3d.com/ScriptReference/Rect.html

2. 代码：

using UnityEngine;
using UnityEngine.EventSystems;

public class DragMovePanel : MonoBehaviour, IPointerDownHandler, IDragHandler
{
    private Vector2 originalLocalPointerPosition;
    private Vector3 originalPanelLocalPosition;
    private RectTransform panelRectTransform;
    private RectTransform parentRectTransform;

    void Awake()
    {
        panelRectTransform = transform.parent as RectTransform;
        parentRectTransform = panelRectTransform.parent as RectTransform;
    }

    public void OnPointerDown(PointerEventData data)
    {
        //计算Panel本地位置
        originalPanelLocalPosition = panelRectTransform.localPosition;

        //计算鼠标点击在Panel父Panel的位置
        RectTransformUtility.ScreenPointToLocalPointInRectangle(parentRectTransform, data.position, data.pressEventCamera, out originalLocalPointerPosition);
    }

    public void OnDrag(PointerEventData data)
    {
        if (panelRectTransform == null || parentRectTransform == null)
            return;

        Vector2 localPointerPosition;
        if (RectTransformUtility.ScreenPointToLocalPointInRectangle(parentRectTransform, data.position, data.pressEventCamera, out localPointerPosition))
        {
            Vector3 offsetToOriginal = localPointerPosition - originalLocalPointerPosition;//计算鼠标偏移
            panelRectTransform.localPosition = originalPanelLocalPosition + offsetToOriginal;
        }

        ClampToWindow();
    }

    // Clamp panel to area of parent
    void ClampToWindow()
    {
        //参考：https://docs.unity3d.com/ScriptReference/Rect.html
        //以Pivot为中心，min是左上角相对Pivot的坐标，max是右下角相对Pivot的坐标
        Vector3 pos = panelRectTransform.localPosition;
        Vector3 minPosition = parentRectTransform.rect.min - panelRectTransform.rect.min;//相减为两中心点的向量
        Vector3 maxPosition = parentRectTransform.rect.max - panelRectTransform.rect.max;

        //Debug.Log("panelRectTransform.rect.min= " + panelRectTransform.rect.min);
        //Debug.Log("panelRectTransform.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;
    }
}

三. 修改Panel大小

1. 注意点

• sizeDelta：
  • 为Vector2类型
  • 如果锚点在一起，那么sizeDelta为矩形的大小，即右边Inspector中Width和Heigh
  • 如果锚点分开，那么sizeDelta表示为矩形比锚点组成的矩形大小多少，数值为右边Left+Right，Top+Buttom的绝对值

2. 代码：

using UnityEngine;
using UnityEngine.EventSystems;

public class ResizePanel : MonoBehaviour, IPointerDownHandler, IDragHandler
{
    public Vector2 minSize = new Vector2(100, 100);
    public Vector2 maxSize = new Vector2(400, 400);

    private RectTransform panelRectTransform;
    private Vector2 originalLocalPointerPosition;
    private Vector2 originalSizeDelta;

    void Awake()
    {
        panelRectTransform = transform.parent.GetComponent<RectTransform>();
    }

    public void OnPointerDown(PointerEventData data)
    {
        originalSizeDelta = panelRectTransform.sizeDelta;
        RectTransformUtility.ScreenPointToLocalPointInRectangle(panelRectTransform, data.position, data.pressEventCamera, out originalLocalPointerPosition);
    }

    public void OnDrag(PointerEventData data)
    {
        if (panelRectTransform == null)
            return;

        //鼠标偏移量
        Vector2 localPointerPosition;
        RectTransformUtility.ScreenPointToLocalPointInRectangle(panelRectTransform, data.position, data.pressEventCamera, out localPointerPosition);
        Vector3 offsetToOriginal = localPointerPosition - originalLocalPointerPosition;

        Vector2 sizeDelta = originalSizeDelta + new Vector2(offsetToOriginal.x, -offsetToOriginal.y);
        sizeDelta = new Vector2(
            Mathf.Clamp(sizeDelta.x, minSize.x, maxSize.x),
            Mathf.Clamp(sizeDelta.y, minSize.y, maxSize.y)
        );

        panelRectTransform.sizeDelta = sizeDelta;
    }
}