操作說明：使用幾何當做參數進行點擊測試

這個範例示範如何在使用 Geometry 作為點擊測試參數的視覺物件上執行點擊測試。

範例

下列範例示範如何使用 HitTest 方法的 GeometryHitTestParameters 來設定點擊測試。 傳遞至 OnMouseDown 方法的 Point 值是用來建立 Geometry 物件，以延伸點擊測試的範圍。

// Respond to the mouse button down event by setting up a hit test results callback.
private void OnMouseDown(object sender, MouseButtonEventArgs e)
{
    // Retrieve the coordinate of the mouse position.
    Point pt = e.GetPosition((UIElement)sender);

    // Expand the hit test area by creating a geometry centered on the hit test point.
    EllipseGeometry expandedHitTestArea = new EllipseGeometry(pt, 10.0, 10.0);

    // Clear the contents of the list used for hit test results.
    hitResultsList.Clear();

    // Set up a callback to receive the hit test result enumeration.
    VisualTreeHelper.HitTest(myControl, null,
        new HitTestResultCallback(MyHitTestResultCallback),
        new GeometryHitTestParameters(expandedHitTestArea));

    // Perform actions on the hit test results list.
    if (hitResultsList.Count > 0)
    {
        ProcessHitTestResultsList();
    }
}

' Respond to the mouse button down event by setting up a hit test results callback.
Private Overloads Sub OnMouseDown(ByVal sender As Object, ByVal e As MouseButtonEventArgs)
    ' Retrieve the coordinate of the mouse position.
    Dim pt As Point = e.GetPosition(CType(sender, UIElement))

    ' Expand the hit test area by creating a geometry centered on the hit test point.
    Dim expandedHitTestArea As New EllipseGeometry(pt, 10.0, 10.0)

    ' Clear the contents of the list used for hit test results.
    hitResultsList.Clear()

    ' Set up a callback to receive the hit test result enumeration.
    VisualTreeHelper.HitTest(myControl, Nothing, New HitTestResultCallback(AddressOf MyHitTestResultCallback), New GeometryHitTestParameters(expandedHitTestArea))

    ' Perform actions on the hit test results list.
    If hitResultsList.Count > 0 Then
        ProcessHitTestResultsList()
    End If
End Sub

GeometryHitTestResult 的 IntersectionDetail 屬性會提供點擊測試結果的相關資訊，該測試使用 Geometry 作為點擊測試參數。 下圖顯示點擊測試幾何 (藍色圓形) 和目標視覺物件呈現內容 (紅色矩形) 之間的關係。

顯示點擊測試中所使用 IntersectionDetail 的圖表。

下列範例示範如何在使用 Geometry 作為點擊測試參數時實作點擊測試回呼。 result 參數會轉換成 GeometryHitTestResult，以擷取 IntersectionDetail 屬性的值。 屬性值可讓您判斷 Geometry 點擊測試參數是完整或部分包含在點擊測試目標呈現的內容內。 在此情況下，範例程式碼僅將點擊測試結果加入至完全包含在目標範圍內之視覺效果的清單中。

// Return the result of the hit test to the callback.
public HitTestResultBehavior MyHitTestResultCallback(HitTestResult result)
{
    // Retrieve the results of the hit test.
    IntersectionDetail intersectionDetail = ((GeometryHitTestResult)result).IntersectionDetail;

    switch (intersectionDetail)
    {
        case IntersectionDetail.FullyContains:

            // Add the hit test result to the list that will be processed after the enumeration.
            hitResultsList.Add(result.VisualHit);

            return HitTestResultBehavior.Continue;

        case IntersectionDetail.Intersects:

            // Set the behavior to return visuals at all z-order levels.
            return HitTestResultBehavior.Continue;

        case IntersectionDetail.FullyInside:

            // Set the behavior to return visuals at all z-order levels.
            return HitTestResultBehavior.Continue;

        default:
            return HitTestResultBehavior.Stop;
    }
}

' Return the result of the hit test to the callback.
Public Function MyHitTestResultCallback(ByVal result As HitTestResult) As HitTestResultBehavior
    ' Retrieve the results of the hit test.
    Dim intersectionDetail As IntersectionDetail = (CType(result, GeometryHitTestResult)).IntersectionDetail

    Select Case intersectionDetail
        Case IntersectionDetail.FullyContains

            ' Add the hit test result to the list that will be processed after the enumeration.
            hitResultsList.Add(result.VisualHit)

            Return HitTestResultBehavior.Continue

        Case IntersectionDetail.Intersects

            ' Set the behavior to return visuals at all z-order levels.
            Return HitTestResultBehavior.Continue

        Case IntersectionDetail.FullyInside

            ' Set the behavior to return visuals at all z-order levels.
            Return HitTestResultBehavior.Continue

        Case Else
            Return HitTestResultBehavior.Stop
    End Select
End Function

另請參閱

• 視覺分層中的點擊測試
• 對視覺物件中的幾何進行點擊測試