通过

如何：对 Visual 中的几何图形进行命中测试

  • 项目

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。

另请参阅