Unity实现新手引导镂空效果

using UnityEngine;
using UnityEngine.UI;
 
/// <summary>
/// 实现镂空效果的Mask组件
/// </summary>
public class HollowOutMask : MaskableGraphic, ICanvasRaycastFilter
{
 [SerializeField]
 private RectTransform _target;
 
 private Vector3 _targetMin = Vector3.zero;
 private Vector3 _targetMax = Vector3.zero;
 
 private bool _canRefresh = true;
 private Transform _cacheTrans = null;
 
 /// <summary>
 /// 设置镂空的目标
 /// </summary>
 public void SetTarget(RectTransform target)
 {
 _canRefresh = true;
 _target = target;
 _RefreshView();
 }
 
 private void _SetTarget(Vector3 tarMin, Vector3 tarMax)
 {
 if (tarMin == _targetMin && tarMax == _targetMax)
 return;
 _targetMin = tarMin;
 _targetMax = tarMax;
 SetAllDirty();
 }
 
 private void _RefreshView()
 {
 if (!_canRefresh) return;
 _canRefresh = false;
 
 if (null == _target)
 {
 _SetTarget(Vector3.zero, Vector3.zero);
 SetAllDirty();
 }
 else
 {
 Bounds bounds = RectTransformUtility.CalculateRelativeRectTransformBounds(_cacheTrans, _target);
 _SetTarget(bounds.min, bounds.max);
 }
 }
 
 protected override void OnPopulateMesh(VertexHelper vh)
 {
 if (_targetMin == Vector3.zero && _targetMax == Vector3.zero)
 {
 base.OnPopulateMesh(vh);
 return;
 }
 
 vh.Clear();
 
 // 填充顶点
 UIVertex vert = UIVertex.simpleVert;
 vert.color = color;
 
 Vector2 selfPiovt = rectTransform.pivot;
 Rect selfRect = rectTransform.rect;
 float outerLx = -selfPiovt.x * selfRect.width;
 float outerBy = -selfPiovt.y * selfRect.height;
 float outerRx = (1 - selfPiovt.x) * selfRect.width;
 float outerTy = (1 - selfPiovt.y) * selfRect.height;
 // 0 - Outer:LT
 vert.position = new Vector3(outerLx, outerTy);
 vh.AddVert(vert);
 // 1 - Outer:RT
 vert.position = new Vector3(outerRx, outerTy);
 vh.AddVert(vert);
 // 2 - Outer:RB
 vert.position = new Vector3(outerRx, outerBy);
 vh.AddVert(vert);
 // 3 - Outer:LB
 vert.position = new Vector3(outerLx, outerBy);
 vh.AddVert(vert);
 
 // 4 - Inner:LT
 vert.position = new Vector3(_targetMin.x, _targetMax.y);
 vh.AddVert(vert);
 // 5 - Inner:RT
 vert.position = new Vector3(_targetMax.x, _targetMax.y);
 vh.AddVert(vert);
 // 6 - Inner:RB
 vert.position = new Vector3(_targetMax.x, _targetMin.y);
 vh.AddVert(vert);
 // 7 - Inner:LB
 vert.position = new Vector3(_targetMin.x, _targetMin.y);
 vh.AddVert(vert);
 
 // 设定三角形
 vh.AddTriangle(4, 0, 1);
 vh.AddTriangle(4, 1, 5);
 vh.AddTriangle(5, 1, 2);
 vh.AddTriangle(5, 2, 6);
 vh.AddTriangle(6, 2, 3);
 vh.AddTriangle(6, 3, 7);
 vh.AddTriangle(7, 3, 0);
 vh.AddTriangle(7, 0, 4);
 }
 
 bool ICanvasRaycastFilter.IsRaycastLocationValid(Vector2 screenPos, Camera eventCamera)
 {
 if (null == _target) return true;
 // 将目标对象范围内的事件镂空（使其穿过）
 return !RectTransformUtility.RectangleContainsScreenPoint(_target, screenPos, eventCamera);
 }
 
 protected override void Awake()
 {
 base.Awake();
 _cacheTrans = GetComponent<RectTransform>();
 }
 
#if UNITY_EDITOR
 void Update()
 {
 _canRefresh = true;
 _RefreshView();
 }
#endif
}