HOW TO：對 Visual 中的幾何進行點擊測試

本範例示範如何在由一個或多個 Geometry 物件組成的視覺物件上執行點擊測試 (Hit Test)。

範例

下列範例示範如何從使用 GetDrawing 方法的視覺物件擷取 DrawingGroup。 接著在 DrawingGroup 中每個繪圖的呈現內容上執行點擊測試，以確定點擊的幾何圖案。

注意事項
在大部分的情況下，您都可以使用 HitTest 方法，判斷某個點是否與視覺項目的任何呈現內容交集。

        ' 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

// 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.
            }
        }

    }
}

FillContains 方法是一種多載方法，可以讓您使用指定的 Point 或 Geometry 進行點擊測試。 如果為幾何圖案描邊，描邊部分可能會超出填色週框。 在這種情況下，除了 FillContains 之外，您可能還需要呼叫 StrokeContains。

您也可以提供 ToleranceType，以達到貝茲簡維化的目的。

注意事項
這個範例並未考慮幾何圖案上可能套用的任何轉換或裁剪設定。此外，此範例也不會使用樣式控制項，因為它沒有任何與其直接關聯的繪圖。

請參閱

工作

HOW TO：使用幾何當做參數進行點擊測試

概念

視覺分層中的點擊測試