在另一個ScrollViewer中包裝列表框的解決方法允許以犧牲冗餘ScrollViewer控件爲代價的全部XAML解決方案(請參閱問題中的評論)。最後,我的隊友決定採用如下代碼隱藏解決方案。
下面是我們需要訪問ScrollViewer的ListBox的相關屬性。
<ListBox Name="_listBox" ScrollViewer.HorizontalScrollBarVisibility="Disabled"
Loaded="InitializeListBoxScrollViewerProperty"/>
這裏是隱藏滾動查看器以供外部控件使用的代碼隱藏。
private static readonly DependencyPropertyKey ListBoxScrollViewerPropertyKey =
DependencyProperty.RegisterReadOnly("ListBoxScrollViewer", typeof(ScrollViewer),
typeof(MyEditView), new PropertyMetadata());
protected static readonly DependencyProperty ListBoxScrollViewerProperty =
ListBoxScrollViewerPropertyKey.DependencyProperty;
protected ScrollViewer ListBoxScrollViewer
{
get { return (ScrollViewer)GetValue(ListBoxScrollViewerProperty); }
private set { SetValue(ListBoxScrollViewerPropertyKey, value); }
}
private void InitializeListBoxScrollViewerProperty(object sender, RoutedEventArgs args)
{
if (ReferenceEquals(args.OriginalSource, _listBox))
{
var scrollViewer = _listBox.GetFirstDescendantBreadthFirst<ScrollViewer>();
if (scrollViewer != null)
{
ListBoxScrollViewer = scrollViewer;
}
}
}
下面是使用的擴展方法:
public static class DependencyObjectExtensions
{
public static TDescendant GetFirstDescendantBreadthFirst<TDescendant>
(this DependencyObject dependencyObject) where TDescendant : DependencyObject
{
if (dependencyObject == null) { throw new ArgumentNullException(); }
return GetFirstDescendantBreadthFirst<TDescendant>(GetAllChildren(dependencyObject));
}
private static TDescendant GetFirstDescendantBreadthFirst<TDescendant>
(IEnumerable<DependencyObject> descendants) where TDescendant : DependencyObject
{
if (!descendants.Any()) return null;
var descendant = descendants.OfType<TDescendant>().FirstOrDefault();
if (descendant != null) return descendant;
return GetFirstDescendantBreadthFirst<TDescendant>(descendants.SelectMany(GetAllChildren));
}
private static IEnumerable<DependencyObject> GetAllChildren(DependencyObject dependencyObject)
{
return Enumerable
.Range(0, VisualTreeHelper.GetChildrenCount(dependencyObject))
.Select(i => VisualTreeHelper.GetChild(dependencyObject, i));
}
}
最後,滾動觀衆可以在XAML的另一部分進行訪問。
<Grid>
<Grid.Style>
<Style TargetType="Grid">
<Style.Triggers>
<DataTrigger Binding="{Binding ListBoxScrollViewer.ComputedVerticalScrollBarVisibility,
RelativeSource={RelativeSource AncestorType=l:MyEditView}}" Value="Visible">
<Setter Property="Margin" Value="{StaticResource myWidenedMargin}"/>
</DataTrigger>
</Style.Triggers>
</Style>
</Grid.Style>
</Grid>
從我所知道的情況來看,在ListBox的「部件」中往往會很困難。我現在最好的解決方法是禁用ListBox中的滾動條並將ListBox包裝在ScrollViewer中。然後DataTrigger可以工作,如果我綁定到包裝ScrollViewer元素名稱並將Path設置爲ComputedVerticalScrollBarVisibility。 –