如何:对 Visual 中的几何图形进行命中测试
此示例演示如何对由一个或多个 Geometry 对象组成的视觉对象执行命中测试。
示例
以下示例显示如何从使用 GetDrawing 方法的视觉对象中检索 DrawingGroup。 随后,此示例对 DrawingGroup 中每个绘图所呈现的内容执行命中测试,以确定命中了哪个几何图形。
注意
在大多数情况下,将使用 HitTest 方法来确定点是否与视觉对象的任何呈现内容有交集。
// Determine if a geometry within the visual was hit.
static public void HitTestGeometryInVisual(Visual visual, Point pt)
{
// Retrieve the group of drawings for the visual.
DrawingGroup drawingGroup = VisualTreeHelper.GetDrawing(visual);
EnumDrawingGroup(drawingGroup, pt);
}
// Enumerate the drawings in the DrawingGroup.
static public void EnumDrawingGroup(DrawingGroup drawingGroup, Point pt)
{
DrawingCollection drawingCollection = drawingGroup.Children;
// Enumerate the drawings in the DrawingCollection.
foreach (Drawing drawing in drawingCollection)
{
// If the drawing is a DrawingGroup, call the function recursively.
if (drawing.GetType() == typeof(DrawingGroup))
{
EnumDrawingGroup((DrawingGroup)drawing, pt);
}
else if (drawing.GetType() == typeof(GeometryDrawing))
{
// Determine whether the hit test point falls within the geometry.
if (((GeometryDrawing)drawing).Geometry.FillContains(pt))
{
// Perform action based on hit test on geometry.
}
}
}
}
' Determine if a geometry within the visual was hit.
Public Shared Sub HitTestGeometryInVisual(ByVal visual As Visual, ByVal pt As Point)
' Retrieve the group of drawings for the visual.
Dim drawingGroup As DrawingGroup = VisualTreeHelper.GetDrawing(visual)
EnumDrawingGroup(drawingGroup, pt)
End Sub
' Enumerate the drawings in the DrawingGroup.
Public Shared Sub EnumDrawingGroup(ByVal drawingGroup As DrawingGroup, ByVal pt As Point)
Dim drawingCollection As DrawingCollection = drawingGroup.Children
' Enumerate the drawings in the DrawingCollection.
For Each drawing As Drawing In drawingCollection
' If the drawing is a DrawingGroup, call the function recursively.
If drawing.GetType() Is GetType(DrawingGroup) Then
EnumDrawingGroup(CType(drawing, DrawingGroup), pt)
ElseIf drawing.GetType() Is GetType(GeometryDrawing) Then
' Determine whether the hit test point falls within the geometry.
If (CType(drawing, GeometryDrawing)).Geometry.FillContains(pt) Then
' Perform action based on hit test on geometry.
End If
End If
Next drawing
End Sub
FillContains 方法是一种重载方法,支持通过使用指定的 Point 或 Geometry 命中测试。 绘制几何图形时,笔画可以延伸到填充边界之外。 在此情况下,除了 FillContains,你可能还需要调用 StrokeContains。
还可以提供一个 ToleranceType 以用于贝塞尔拉平操作。
注意
此示例并未考虑可能应用到几何图形中的任何变形或剪裁。 此外,此示例不会使用已设置样式的控件,因为这种控件没有与它直接关联的绘图。