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mirror of synced 2024-11-14 09:29:17 +00:00

Added missing ListBoxAutoScroll

This commit is contained in:
PsychoMark 2016-06-20 14:20:55 +02:00
parent 7785b6a0ed
commit ceb2e386f4

View File

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using System;
using System.Collections;
using System.Collections.Specialized;
using System.Windows;
using System.Windows.Data;
using System.Windows.Controls;
using System.Windows.Media;
namespace PettingZoo.Infrastructure
{
// Source: https://social.msdn.microsoft.com/Forums/vstudio/en-US/0f524459-b14e-4f9a-8264-267953418a2d/trivial-listboxlistview-autoscroll?forum=wpf
//
// Slightly modified version; takes into account the current scroll position of the ListBox,
// so the end user can scroll up without getting dragged down again.
public static class ListBox
{
public static readonly DependencyProperty AutoScrollProperty =
DependencyProperty.RegisterAttached("AutoScroll", typeof (bool), typeof (System.Windows.Controls.ListBox),
new PropertyMetadata(false));
public static readonly DependencyProperty AutoScrollHandlerProperty =
DependencyProperty.RegisterAttached("AutoScrollHandler", typeof (AutoScrollHandler),
typeof (System.Windows.Controls.ListBox));
public static bool GetAutoScroll(System.Windows.Controls.ListBox instance)
{
return (bool) instance.GetValue(AutoScrollProperty);
}
public static void SetAutoScroll(System.Windows.Controls.ListBox instance, bool value)
{
var oldHandler = (AutoScrollHandler) instance.GetValue(AutoScrollHandlerProperty);
if (oldHandler != null)
{
oldHandler.Dispose();
instance.SetValue(AutoScrollHandlerProperty, null);
}
instance.SetValue(AutoScrollProperty, value);
if (value)
instance.SetValue(AutoScrollHandlerProperty, new AutoScrollHandler(instance));
}
}
public class AutoScrollHandler : DependencyObject, IDisposable
{
public static readonly DependencyProperty ItemsSourceProperty =
DependencyProperty.Register("ItemsSource", typeof (IEnumerable),
typeof (AutoScrollHandler), new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.None,
ItemsSourcePropertyChanged));
private readonly System.Windows.Controls.ListBox target;
private ScrollViewer scrollViewer = null;
public AutoScrollHandler(System.Windows.Controls.ListBox target)
{
this.target = target;
var binding = new Binding("ItemsSource")
{
Source = this.target
};
BindingOperations.SetBinding(this, ItemsSourceProperty, binding);
}
public void Dispose()
{
BindingOperations.ClearBinding(this, ItemsSourceProperty);
}
public IEnumerable ItemsSource
{
get { return (IEnumerable) GetValue(ItemsSourceProperty); }
set { SetValue(ItemsSourceProperty, value); }
}
private static void ItemsSourcePropertyChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
{
((AutoScrollHandler) o).ItemsSourceChanged((IEnumerable) e.OldValue, (IEnumerable) e.NewValue);
}
private void ItemsSourceChanged(IEnumerable oldValue, IEnumerable newValue)
{
var collection = oldValue as INotifyCollectionChanged;
if (collection != null)
collection.CollectionChanged -= Collection_CollectionChanged;
collection = newValue as INotifyCollectionChanged;
if (collection != null)
collection.CollectionChanged += Collection_CollectionChanged;
}
private void Collection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
if (e.Action != NotifyCollectionChangedAction.Add || e.NewItems == null || e.NewItems.Count < 1)
return;
// Resolve on demand; in the constructor FindScrollViewer will return null
if (scrollViewer == null)
{
scrollViewer = FindScrollViewer(target);
if (scrollViewer == null)
return;
}
if (Math.Abs(scrollViewer.VerticalOffset - scrollViewer.ScrollableHeight) < 1)
target.ScrollIntoView(e.NewItems[e.NewItems.Count - 1]);
}
private static ScrollViewer FindScrollViewer(DependencyObject parent)
{
var childCount = VisualTreeHelper.GetChildrenCount(parent);
for (var childIndex = 0; childIndex < childCount; childIndex++)
{
var child = VisualTreeHelper.GetChild(parent, childIndex);
var scrollViewer = (child as ScrollViewer);
if (scrollViewer != null)
return scrollViewer;
scrollViewer = FindScrollViewer(child);
if (scrollViewer != null)
return scrollViewer;
}
return null;
}
}
}