Question

当使用OnRender在屏幕上绘制内容时，有没有办法在绘制的图形上执行命中测试？

示例代码

    protected override void OnRender(System.Windows.Media.DrawingContext drawingContext)
    {
        base.OnRender(drawingContext);

        drawingContext.DrawRectangle(Brushes.Black, null, new Rect(50, 50, 100, 100));
    }

显然，没有人参考绘制的矩形，这对于执行命中测试是必要的，还是我错了？我知道我可以使用DrawingVisual，我只是好奇我的理解是否正确，使用OnRender绘制的东西你不能对绘制的东西进行任何命中测试？

Answer 1

您理解正确，无法对使用DrawingContext方法绘制的图形进行测试，因为它们未在可视树中表示为对象。

Answer 2

除非我完全误解了OP的问题，否则答案是肯定的，命中测试是基于在OnRender期间绘制的内容。您可以通过在覆盖OnMouseEnter的同一个类中覆盖OnRender来判断。在覆盖OnMouseEnter时尝试这个：

var htr = VisualTreeHelper.HitTest(this, e.GetPosition(this));
if (htr != null)
     System.Diagnostics.Debug.WriteLine("It's a hit!");

现在，我注意到你仍在调用base.OnRender，这表明你正试图绘制Visual否则会呈现的内容。那么，你所能做的就是区分父类呈现的内容与你在覆盖中呈现的内容。但是，如果您需要，只需将您的绘图包含在自己的Visual。

中

Answer 3

我的快速解决方案。它在许多方面都不理想，但它对我来说是一个开始。如果有必要，可以轻松地重构性能。

    /// <summary>
    /// Provides basic hit testing
    /// </summary>
    public class RadarHitTestUtility
    {
        public Dictionary<Tuple<int,int>, HitContainer> HitStorage = new Dictionary<Tuple<int, int>, HitContainer>();

        public void AddEllipse(RadarObject radarObject, Point point, double x, double y)
        {
            // Geometry used for hit testing
            var elipse = new EllipseGeometry
            {
                Center = point,
                RadiusX = x,
                RadiusY = y,
            };

            var key = new Tuple<int, int>((int)point.X, (int)point.Y);

            var hit = new HitContainer
            {
                Geometry = elipse,
                Bounds = elipse.Bounds,
                RadarObject = radarObject
            };

            if(!HitStorage.ContainsKey(key))
                HitStorage.Add(key, hit);
        }

        /// <summary>
        /// Gets first radar object whose center point is within distance of point.
        /// </summary>
        public HitContainer GetSimpleHit(Point point, int distance = 5)
        {
            foreach (var hit in HitStorage)
            {
                if (Math.Abs(hit.Key.Item1 - point.X) <= distance && Math.Abs(hit.Key.Item2 - point.Y) <= distance)
                {
                    hit.Value.Intersection = IntersectionDetail.NotCalculated;
                    return hit.Value;
                }
            }
            return default(HitContainer);
        }

        /// <summary>
        /// Gets first radar object that contains point
        /// </summary>
        public HitContainer GetHit(Point point)
        {
            var PreCheckDistance = 50;

            foreach (var hit in HitStorage)
            {
                if (Math.Abs(hit.Key.Item1 - point.X) <= PreCheckDistance && Math.Abs(hit.Key.Item2 - point.Y) <= PreCheckDistance)
                {
                    if (hit.Value.Geometry.FillContains(point))
                    {
                        hit.Value.Intersection = IntersectionDetail.FullyInside;
                        return hit.Value;
                    }                    
                }
            }
            return default(HitContainer);
        }

        /// <summary>
        /// Gets first radar object that intersects with geometry
        /// </summary>
        public HitContainer GetHit(Geometry geometry)
        {
            var PreCheckDistance = 50;
            var GeometryCheckTolerance = 1;
            var center = geometry.Bounds.Center();

            foreach (var hit in HitStorage)
            {
                if (Math.Abs(hit.Key.Item1 - center.X) <= PreCheckDistance && Math.Abs(hit.Key.Item2 - center.Y) <= PreCheckDistance)
                {
                    var result = hit.Value.Geometry.FillContainsWithDetail(geometry, GeometryCheckTolerance, ToleranceType.Absolute);
                    if (result != IntersectionDetail.Empty)
                    {
                        hit.Value.Intersection = result;
                        return hit.Value;
                    }
                }
            }
            return default(HitContainer);
        }

        public class HitContainer
        {
            public RadarObject RadarObject { get; set; }
            public Geometry Geometry { get; set; }
            public Rect Bounds { get; set; }
            public IntersectionDetail Intersection { get; set; }
        }

        public void Clear()
        {
            HitStorage.Clear();
        }
    }

在控件中声明一个实例

public RadarHitTestUtility HitTester = new RadarHitTestUtility();

您需要在某个时刻调用Clear（），以便命中测试集合中只存在当前对象。

HitTester.Clear();

在OnRender（）中，如果要为记录测试目的记录绘图调用，可以使用AddEllipse（）

进行记录。

HitTester.AddEllipse(radarObject, radarObject.Point, actorRadius, actorRadius);

以下是我要求点击检查的方式

    private void MouseDownHandler(object sender, MouseButtonEventArgs e)
    {
        IsMouseDown = true;
        Cursor = Cursors.Hand;
        DragInitialPosition = Mouse.GetPosition(this);
        DragInitialPanOffset = CanvasData.PanOffset;

        var hit = FindElementUnderClick(sender, e);
        if (hit != null)
        {
            SelectedItem = hit.RadarObject.Actor;
        }            
    }

    private RadarHitTestUtility.HitContainer FindElementUnderClick(object sender, MouseEventArgs e)
    {
        var position = e.GetPosition((UIElement)sender);            
        return HitTester.GetHit(position);
    }

如果你想测试椭圆以外的形状你只需要在RadarHitTestUtility中添加适当的记录方法并调用它，创建一个不同类型的几何来测试。

WPF：OnRender和命中测试

3 个答案: