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July 30, 2018 08:57
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using System.Collections.Generic; | |
using System.Windows; | |
using System.Windows.Media; | |
namespace Hardcodet.Wpf.Util | |
{ | |
/// <summary> | |
/// Helper methods for UI-related tasks. | |
/// </summary> | |
public static class TreeHelper | |
{ | |
#region find parent | |
/// <summary> | |
/// Finds a parent of a given item on the visual tree. | |
/// </summary> | |
/// <typeparam name="T">The type of the queried item.</typeparam> | |
/// <param name="child">A direct or indirect child of the | |
/// queried item.</param> | |
/// <returns>The first parent item that matches the submitted | |
/// type parameter. If not matching item can be found, a null | |
/// reference is being returned.</returns> | |
public static T TryFindParent<T>(this DependencyObject child) | |
where T : DependencyObject | |
{ | |
//get parent item | |
DependencyObject parentObject = GetParentObject(child); | |
//we've reached the end of the tree | |
if (parentObject == null) return null; | |
//check if the parent matches the type we're looking for | |
T parent = parentObject as T; | |
if (parent != null) | |
{ | |
return parent; | |
} | |
else | |
{ | |
//use recursion to proceed with next level | |
return TryFindParent<T>(parentObject); | |
} | |
} | |
/// <summary> | |
/// This method is an alternative to WPF's | |
/// <see cref="VisualTreeHelper.GetParent"/> method, which also | |
/// supports content elements. Keep in mind that for content element, | |
/// this method falls back to the logical tree of the element! | |
/// </summary> | |
/// <param name="child">The item to be processed.</param> | |
/// <returns>The submitted item's parent, if available. Otherwise | |
/// null.</returns> | |
public static DependencyObject GetParentObject(this DependencyObject child) | |
{ | |
if (child == null) return null; | |
//handle content elements separately | |
ContentElement contentElement = child as ContentElement; | |
if (contentElement != null) | |
{ | |
DependencyObject parent = ContentOperations.GetParent(contentElement); | |
if (parent != null) return parent; | |
FrameworkContentElement fce = contentElement as FrameworkContentElement; | |
return fce != null ? fce.Parent : null; | |
} | |
//also try searching for parent in framework elements (such as DockPanel, etc) | |
FrameworkElement frameworkElement = child as FrameworkElement; | |
if (frameworkElement != null) | |
{ | |
DependencyObject parent = frameworkElement.Parent; | |
if (parent != null) return parent; | |
} | |
//if it's not a ContentElement/FrameworkElement, rely on VisualTreeHelper | |
return VisualTreeHelper.GetParent(child); | |
} | |
#endregion | |
#region find children | |
/// <summary> | |
/// Analyzes both visual and logical tree in order to find all elements of a given | |
/// type that are descendants of the <paramref name="source"/> item. | |
/// </summary> | |
/// <typeparam name="T">The type of the queried items.</typeparam> | |
/// <param name="source">The root element that marks the source of the search. If the | |
/// source is already of the requested type, it will not be included in the result.</param> | |
/// <returns>All descendants of <paramref name="source"/> that match the requested type.</returns> | |
public static IEnumerable<T> FindChildren<T>(this DependencyObject source) where T : DependencyObject | |
{ | |
if (source != null) | |
{ | |
var childs = GetChildObjects(source); | |
foreach (DependencyObject child in childs) | |
{ | |
//analyze if children match the requested type | |
if (child != null && child is T) | |
{ | |
yield return (T)child; | |
} | |
//recurse tree | |
foreach (T descendant in FindChildren<T>(child)) | |
{ | |
yield return descendant; | |
} | |
} | |
} | |
} | |
/// <summary> | |
/// This method is an alternative to WPF's | |
/// <see cref="VisualTreeHelper.GetChild"/> method, which also | |
/// supports content elements. Keep in mind that for content elements, | |
/// this method falls back to the logical tree of the element. | |
/// </summary> | |
/// <param name="parent">The item to be processed.</param> | |
/// <returns>The submitted item's child elements, if available.</returns> | |
public static IEnumerable<DependencyObject> GetChildObjects(this DependencyObject parent) | |
{ | |
if (parent == null) yield break; | |
if (parent is ContentElement || parent is FrameworkElement) | |
{ | |
//use the logical tree for content / framework elements | |
foreach (object obj in LogicalTreeHelper.GetChildren(parent)) | |
{ | |
var depObj = obj as DependencyObject; | |
if (depObj != null) yield return (DependencyObject)obj; | |
} | |
} | |
else | |
{ | |
//use the visual tree per default | |
int count = VisualTreeHelper.GetChildrenCount(parent); | |
for (int i = 0; i < count; i++) | |
{ | |
yield return VisualTreeHelper.GetChild(parent, i); | |
} | |
} | |
} | |
#endregion | |
#region find from point | |
/// <summary> | |
/// Tries to locate a given item within the visual tree, | |
/// starting with the dependency object at a given position. | |
/// </summary> | |
/// <typeparam name="T">The type of the element to be found | |
/// on the visual tree of the element at the given location.</typeparam> | |
/// <param name="reference">The main element which is used to perform | |
/// hit testing.</param> | |
/// <param name="point">The position to be evaluated on the origin.</param> | |
public static T TryFindFromPoint<T>(UIElement reference, Point point) | |
where T : DependencyObject | |
{ | |
DependencyObject element = reference.InputHitTest(point) as DependencyObject; | |
if (element == null) return null; | |
else if (element is T) return (T)element; | |
else return TryFindParent<T>(element); | |
} | |
#endregion | |
} | |
} |
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