当使用 OnRender 在屏幕上绘制某些东西时，有什么方法可以对绘制的图形进行命中测试？
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，没有参考执行命中测试所必需的绘制的 Rectangle 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执行任何命中测试？
您理解正确，没有办法对您使用 DrawingContext 方法绘制的图形进行命中测试，因为它们在可视化树中没有表示为对象。
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OnRender. 您可以通过OnMouseEnter在您覆盖的同一类中覆盖来判断OnRender。在OnMouseEnter尝试这个覆盖：
var htr = VisualTreeHelper.HitTest(this, e.GetPosition(this));
if (htr != null)
System.Diagnostics.Debug.WriteLine("It's a hit!");
现在，我注意到您仍在打电话base.OnRender，这表明您正在尝试在Visual原本会呈现的内容之上绘制。那么，您将无法做的是区分对父类呈现的内容与您在覆盖中呈现的内容的命中。但是，如果您需要，只需将您的绘图包含在它自己的Visual.
我的快速解决方案。它在很多方面并不理想，但它对我来说是一个开始。如果有必要，可以很容易地重构性能。
/// <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();
}
}
在您的控件中声明一个实例
public RadarHitTestUtility HitTester = new RadarHitTestUtility();
您需要在某个时候调用 Clear()，以便只有当前对象存在于命中测试集合中。
HitTester.Clear();
在 OnRender() 中，当您希望记录绘制调用以用于命中测试时，您可以使用 AddEllipse() 记录它
HitTester.AddEllipse(radarObject, radarObject.Point, actorRadius, actorRadius);
这就是我要求命中检查的方式
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);
}
如果您希望能够测试椭圆以外的形状，您只需将适当的记录方法添加到 RadarHitTestUtility 并调用它，创建一种不同类型的 Geometry 进行测试。