using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

#if UNITY_EDITOR
using UnityEditor;
#endif

[RequireComponent(typeof(PolygonCollider2D))]
public class UIPolygon : Image {

    private PolygonCollider2D _polygon = null;
    private PolygonCollider2D polygon
    {
        get {
            if (_polygon == null)
                _polygon = GetComponent<PolygonCollider2D>();
            return _polygon;
        }
    }

    //设置只响应点击，不进行渲染
    protected UIPolygon()
    {
        useLegacyMeshGeneration = true;
    }

    protected override void OnPopulateMesh(VertexHelper toFill)
    {
        toFill.Clear();
    }

    public override bool IsRaycastLocationValid(Vector2 screenPoint, Camera eventCamera)
    {
        return polygon.OverlapPoint(eventCamera.ScreenToWorldPoint(screenPoint));
    }

#if UNITY_EDITOR
    protected override void Reset()
    {
        base.Reset();
        transform.position = Vector3.zero;
        float w = (rectTransform.sizeDelta.x * 0.5f) + 0.1f;
        float h = (rectTransform.sizeDelta.y * 0.5f) + 0.1f;
        polygon.points = new Vector2[]
            {
                new Vector2(-w,-h),
                new Vector2(w,-h),
                new Vector2(w,h),
                new Vector2(-w,h)
            };
    }
#endif

#if UNITY_EDITOR
    [CustomEditor(typeof(UIPolygon), true)]
    public class UIPolygonInspectorGUI : Editor {
        public override void OnInspectorGUI()
        {
            
        }
    }
#endif
}

把按钮的Image组件和Text组件的Raycast Target取消勾选，在Button下新建一个空物体添加UIPolygon脚本，标记好点击区域就好了。注意，这一检测点击需要使用到相机，所以Canvas的Render Mode要选择相机模式，所用的相机使用正交模式，不然多边形点击区域就会不准了。