//在本例中，通过单独定义的HitTestResultCallback()方法实现回调函数。
//HitTestResultCallback()和GetVisuals()方法都使用命中集合，所以命中集合作为成员字段进行定义。然而，可以通过为回调函数使用匿名方法来避免这一点，
//匿名方法可在GetVisuals()方法内声明
private HitTestResultBehavior HitTestCallback(HitTestResult result)
{
//回调方法实现了命中测试行为。通常HitTestResult对象只提供一个属性(VisualHit)，但可以根据执行命中测试的类型，将他转换成两个派生类型中的任意
//一个。
//如果使用一个点进行命中测试，可将HitTestResult对象转换为PointHitTestResult对象，该类提供了一个不起眼的PointHint属性，该属性返回用于执行
//命中测试的原始点
//如果使用Geometry对象进行命中测试，可将HitTestResult对象转换为GeometryHitTestResult对象，并访问IntersectionDetail属性。IntersectionDetail
//属性告知您几何图形是否完全封装了可视化对象(FullyInside)，几何图形是否与可视化元素只是相互重叠(Intersets)，或者用于命中测试的几何图形是否落
//在可视化元素的内部(FullyContains)
//在本例中，只有当可视化对象完全位于命中测试区域时，才会对命中数量计数。
GeometryHitTestResult geometryResult = (GeometryHitTestResult)result;
DrawingVisual visual = result.VisualHit as DrawingVisual;
if (visual != null && geometryResult.IntersectionDetail == IntersectionDetail.FullyInside)
{
hits.Add(visual);
}
//最后，在回调函数的末尾，可返回两个HitTestResultBehavior枚举值中的一个：
//返回Continue表示继续查找命中，返回Stop则表示结束查找过程
return(HitTestResultBehavior.Continue);
}
private void GridA_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
if (e.LeftButton == MouseButtonState.Released)
{
hits.Clear();
mouseSelectionCounter = 0;
GridA.Children.Remove(pth1);
selectBox = new RectangleGeometry();
recTemp = new Rect();
pth1 = new Path();
//HitTestResult result = VisualTreeHelper.HitTest(GridA, e.GetPosition(this));
//Debug.WriteLine((result.VisualHit as Path).Name);
GeometryHitTestParameters parameters = new GeometryHitTestParameters(recHitResult);
HitTestResultCallback callback = new HitTestResultCallback((HitTestResult result) => {
GeometryHitTestResult geometryResult = (GeometryHitTestResult)result;
Path visual = result.VisualHit as Path;
if (visual != null && geometryResult.IntersectionDetail == IntersectionDetail.FullyInside)
{
hits.Add(visual);
}
return(HitTestResultBehavior.Continue);
});
VisualTreeHelper.HitTest(this, null, callback, parameters);
foreach (Path x in hits)
{
Debug.WriteLine(x.Name);
}
}
}
private HitTestResultBehavior HitTestCallback(HitTestResult result)
{
GeometryHitTestResult geometryResult = (GeometryHitTestResult)result;
if (result.VisualHit is DrawingVisual visual &&
geometryResult.IntersectionDetail == IntersectionDetail.FullyInside)
{
myHits.Add(visual);
}
return(HitTestResultBehavior.Continue);
}
private HitTestResultBehavior HitTestResultCallback(HitTestResult result)
{
GeometryHitTestResult testResult = (GeometryHitTestResult)result;
DrawingVisual visual = result.VisualHit as DrawingVisual;
if (visual != null && testResult.IntersectionDetail == IntersectionDetail.FullyInside)
{
hits.Add(visual);
}
return(HitTestResultBehavior.Continue);
}
/// <summary>
/// Represents a callback that is used to customize hit testing.
/// WPF invokes HitRestResult to report hit test intersections to the user.
/// </summary>
/// <param name="result">The HitTestResult value that represents a visual object that is returned from a hit test.</param>
/// <returns>A HitTestResultBehavior that represents the action resulting from the hit test.</returns>
private HitTestResultBehavior HitTestCallback(HitTestResult result)
{
GeometryHitTestResult geometryResult = (GeometryHitTestResult)result;
DrawingVisual visual = result.VisualHit as DrawingVisual;
// Only include matches that are DrawingVisual objects and that are completely inside the geometry.
if ((visual != null) && (geometryResult.IntersectionDetail == IntersectionDetail.FullyInside))
{
hits.Add(visual);
}
return(HitTestResultBehavior.Continue);
}
private HitTestResultBehavior hitTestResultCallback(HitTestResult result)
{
GeometryHitTestResult geometryHitTest = (GeometryHitTestResult)result;
Rectangle visual = result.VisualHit as Rectangle;
if (visual != null && geometryHitTest.IntersectionDetail == IntersectionDetail.FullyInside)
{
hitResultList.Add(visual);
}
return(HitTestResultBehavior.Continue);
}
/// <summary>
/// Returns a collection of Elements of type targetType that are located in the area of the Geometry geo in the subtree of the UIElement reference
/// </summary>
/// <param name="geo">the geometry which will be tested</param>
/// <param name="reference">specifies the subtree that will be tested</param>
/// <param name="targetType">specifies the type of elements that will be returned (subclasses of this type will also be returned)</param>
/// <returns>A collection of Elements that are found by hittesting with the given parameters</returns>
public static IEnumerable <DependencyObject> GetElementsInGeometry(Geometry geo, Visual reference, Type targetType)
{
List <DependencyObject> results = new List <DependencyObject>();
HitTestFilterCallback filter = (o) =>
{
Type matchType = o.GetType();
//if we find an element of correct type, we can ignore its subtree
//if we find an element of incorrect type, we can ignore it, but must check its children
if (matchType == targetType || matchType.IsSubclassOf(targetType))
{
return(HitTestFilterBehavior.ContinueSkipChildren);
}
else
{
return(HitTestFilterBehavior.ContinueSkipSelf);
}
};
HitTestResultCallback result = (r) =>
{
GeometryHitTestResult ghr = r as GeometryHitTestResult;
if (ghr.IntersectionDetail == IntersectionDetail.Empty)
{
return(HitTestResultBehavior.Continue);
}
Type matchType = r.VisualHit.GetType();
//again we check the type of the element, just to be sure that only correct types go into our collection
if (matchType == targetType || matchType.IsSubclassOf(targetType))
{
results.Add(r.VisualHit);
}
return(HitTestResultBehavior.Continue);
};
VisualTreeHelper.HitTest(reference, filter, result, new GeometryHitTestParameters(geo));
return(results);
}
public static HitTestResult HitTest(Visual root, HitTestFilterCallback filterCallback, HitTestResultCallback resultCallback, HitTestParameters hitTestParameters, HitTestFilterCallback modelCallback)
{
ModelHitTestHelper.HitTestFilterCallbackWrapper filterCallbackWrapper = new ModelHitTestHelper.HitTestFilterCallbackWrapper(filterCallback);
ModelHitTestHelper.HitTestResultCallbackWrapper resultCallbackWrapper = new ModelHitTestHelper.HitTestResultCallbackWrapper(resultCallback, HitTestResultBehavior.Continue);
VisualTreeHelper.HitTest(root, filterCallbackWrapper.FilterCallback, resultCallbackWrapper.ResultCallback, hitTestParameters);
HitTestResult topMostHit = resultCallbackWrapper.TopMostHit;
bool flag = filterCallback == null && resultCallback == null;
VisualHitTestArgs args = new VisualHitTestArgs(root, root, hitTestParameters);
PointHitTestParameters hitTestParameters1 = hitTestParameters as PointHitTestParameters;
GeometryHitTestParameters hitTestParameters2 = hitTestParameters as GeometryHitTestParameters;
foreach (DependencyObject dependencyObject in ModelHitTestHelper.GetDescendantsInZOrder((DependencyObject)root))
{
if (dependencyObject != null)
{
if (filterCallback == null && topMostHit != null && dependencyObject == topMostHit.VisualHit)
{
resultCallbackWrapper.PlayResults();
return(resultCallbackWrapper.TopMostHit);
}
Visual visual = dependencyObject as Visual;
HitTestProvider singletonProvider = ModelHitTestHelper.GetSingletonProvider(dependencyObject);
if (singletonProvider != null && (modelCallback == null || modelCallback((DependencyObject)visual) != HitTestFilterBehavior.Continue))
{
args.UpdateChild(dependencyObject);
HitTestResult result = (HitTestResult)null;
if (hitTestParameters1 != null && visual != null)
{
PointHitTestResult pointHitTestResult = singletonProvider.HitTestPoint(args);
if (pointHitTestResult != null && pointHitTestResult.VisualHit != null)
{
result = (HitTestResult)pointHitTestResult;
}
}
else if (hitTestParameters2 != null && visual != null)
{
GeometryHitTestResult geometryHitTestResult = singletonProvider.HitTestGeometry(args);
if (geometryHitTestResult != null && geometryHitTestResult.IntersectionDetail != IntersectionDetail.Empty && geometryHitTestResult.IntersectionDetail != IntersectionDetail.NotCalculated)
{
result = (HitTestResult)geometryHitTestResult;
}
}
if (result != null)
{
HitTestFilterBehavior testFilterBehavior = filterCallbackWrapper.FilterCallback(dependencyObject);
switch (testFilterBehavior)
{
case HitTestFilterBehavior.Continue:
case HitTestFilterBehavior.Stop:
resultCallbackWrapper.InsertResult(result);
break;
}
if (flag && testFilterBehavior != HitTestFilterBehavior.ContinueSkipSelf || testFilterBehavior == HitTestFilterBehavior.Stop)
{
resultCallbackWrapper.PlayResults();
return(result);
}
}
}
}
}
resultCallbackWrapper.PlayResults();
return(resultCallbackWrapper.TopMostHit);
}
