Make ListView.ScrollIntoView将项目滚动到ListView的中心(C#)
Make ListView.ScrollIntoView将项目滚动到ListView的中心(C#)
提问于 2010-06-01 10:18:49
ListView.ScrollIntoView(object)当前在ListView中查找对象并滚动到该对象。如果您位于要滚动到的对象的下方，则会将该对象滚动到顶行。如果您位于上方，它会将其滚动到最下面一行的视图中。
我想让项目滚动到我的列表视图的中心，如果它当前不可见。有什么简单的方法可以做到这一点吗？
回答 7
Stack Overflow用户
回答已采纳
发布于 2010-06-09 07:10:05
用我写的一个扩展方法，在WPF中很容易做到这一点。要将项滚动到视图中心，只需调用单个方法。
假设您有以下XAML：
<ListView x:Name="view" ItemsSource="{Binding Data}" />
<ComboBox x:Name="box" ItemsSource="{Binding Data}"
SelectionChanged="ScrollIntoView" /> 您的ScrollIntoView方法将非常简单：
private void ScrollIntoView(object sender, SelectionChangedEventArgs e)
{
view.ScrollToCenterOfView(box.SelectedItem);
} 显然，这也可以使用ViewModel来完成，而不是显式地引用控件。
以下是实现。它非常通用，可以处理所有的IScrollInfo可能性。它适用于ListBox或任何其他ItemsControl，也适用于任何面板，包括StackPanel、VirtualizingStackPanel、WrapPanel、DockPanel、Canvas、网格等。
只需将其放入项目中某个位置的.cs文件中：
public static class ItemsControlExtensions
{
public static void ScrollToCenterOfView(this ItemsControl itemsControl, object item)
{
// Scroll immediately if possible
if(!itemsControl.TryScrollToCenterOfView(item))
{
// Otherwise wait until everything is loaded, then scroll
if(itemsControl is ListBox) ((ListBox)itemsControl).ScrollIntoView(item);
itemsControl.Dispatcher.BeginInvoke(DispatcherPriority.Loaded, new Action(() =>
{
itemsControl.TryScrollToCenterOfView(item);
}));
}
}
private static bool TryScrollToCenterOfView(this ItemsControl itemsControl, object item)
{
// Find the container
var container = itemsControl.ItemContainerGenerator.ContainerFromItem(item) as UIElement;
if(container==null) return false;
// Find the ScrollContentPresenter
ScrollContentPresenter presenter = null;
for(Visual vis = container; vis!=null && vis!=itemsControl; vis = VisualTreeHelper.GetParent(vis) as Visual)
if((presenter = vis as ScrollContentPresenter)!=null)
break;
if(presenter==null) return false;
// Find the IScrollInfo
var scrollInfo =
!presenter.CanContentScroll ? presenter :
presenter.Content as IScrollInfo ??
FirstVisualChild(presenter.Content as ItemsPresenter) as IScrollInfo ??
presenter;
// Compute the center point of the container relative to the scrollInfo
Size size = container.RenderSize;
Point center = container.TransformToAncestor((Visual)scrollInfo).Transform(new Point(size.Width/2, size.Height/2));
center.Y += scrollInfo.VerticalOffset;
center.X += scrollInfo.HorizontalOffset;
// Adjust for logical scrolling
if(scrollInfo is StackPanel || scrollInfo is VirtualizingStackPanel)
{
double logicalCenter = itemsControl.ItemContainerGenerator.IndexFromContainer(container) + 0.5;
Orientation orientation = scrollInfo is StackPanel ? ((StackPanel)scrollInfo).Orientation : ((VirtualizingStackPanel)scrollInfo).Orientation;
if(orientation==Orientation.Horizontal)
center.X = logicalCenter;
else
center.Y = logicalCenter;
}
// Scroll the center of the container to the center of the viewport
if(scrollInfo.CanVerticallyScroll) scrollInfo.SetVerticalOffset(CenteringOffset(center.Y, scrollInfo.ViewportHeight, scrollInfo.ExtentHeight));
if(scrollInfo.CanHorizontallyScroll) scrollInfo.SetHorizontalOffset(CenteringOffset(center.X, scrollInfo.ViewportWidth, scrollInfo.ExtentWidth));
return true;
}
private static double CenteringOffset(double center, double viewport, double extent)
{
return Math.Min(extent - viewport, Math.Max(0, center - viewport/2));
}
private static DependencyObject FirstVisualChild(Visual visual)
{
if(visual==null) return null;
if(VisualTreeHelper.GetChildrenCount(visual)==0) return null;
return VisualTreeHelper.GetChild(visual, 0);
}
}Stack Overflow用户
发布于 2010-08-12 01:02:23
Ray Burns上面的出色答案是WPF特有的。
以下是在Silverlight中工作的修改版本：
public static class ItemsControlExtensions
{
public static void ScrollToCenterOfView(this ItemsControl itemsControl, object item)
{
// Scroll immediately if possible
if (!itemsControl.TryScrollToCenterOfView(item))
{
// Otherwise wait until everything is loaded, then scroll
if (itemsControl is ListBox) ((ListBox)itemsControl).ScrollIntoView(item);
itemsControl.Dispatcher.BeginInvoke( new Action(() =>
{
itemsControl.TryScrollToCenterOfView(item);
}));
}
}
private static bool TryScrollToCenterOfView(this ItemsControl itemsControl, object item)
{
// Find the container
var container = itemsControl.ItemContainerGenerator.ContainerFromItem(item) as UIElement;
if (container == null) return false;
// Find the ScrollContentPresenter
ScrollContentPresenter presenter = null;
for (UIElement vis = container; vis != null ; vis = VisualTreeHelper.GetParent(vis) as UIElement)
if ((presenter = vis as ScrollContentPresenter) != null)
break;
if (presenter == null) return false;
// Find the IScrollInfo
var scrollInfo =
!presenter.CanVerticallyScroll ? presenter :
presenter.Content as IScrollInfo ??
FirstVisualChild(presenter.Content as ItemsPresenter) as IScrollInfo ??
presenter;
// Compute the center point of the container relative to the scrollInfo
Size size = container.RenderSize;
Point center = container.TransformToVisual((UIElement)scrollInfo).Transform(new Point(size.Width / 2, size.Height / 2));
center.Y += scrollInfo.VerticalOffset;
center.X += scrollInfo.HorizontalOffset;
// Adjust for logical scrolling
if (scrollInfo is StackPanel || scrollInfo is VirtualizingStackPanel)
{
double logicalCenter = itemsControl.ItemContainerGenerator.IndexFromContainer(container) + 0.5;
Orientation orientation = scrollInfo is StackPanel ? ((StackPanel)scrollInfo).Orientation : ((VirtualizingStackPanel)scrollInfo).Orientation;
if (orientation == Orientation.Horizontal)
center.X = logicalCenter;
else
center.Y = logicalCenter;
}
// Scroll the center of the container to the center of the viewport
if (scrollInfo.CanVerticallyScroll) scrollInfo.SetVerticalOffset(CenteringOffset(center.Y, scrollInfo.ViewportHeight, scrollInfo.ExtentHeight));
if (scrollInfo.CanHorizontallyScroll) scrollInfo.SetHorizontalOffset(CenteringOffset(center.X, scrollInfo.ViewportWidth, scrollInfo.ExtentWidth));
return true;
}
private static double CenteringOffset(double center, double viewport, double extent)
{
return Math.Min(extent - viewport, Math.Max(0, center - viewport / 2));
}
private static DependencyObject FirstVisualChild(UIElement visual)
{
if (visual == null) return null;
if (VisualTreeHelper.GetChildrenCount(visual) == 0) return null;
return VisualTreeHelper.GetChild(visual, 0);
}
} Stack Overflow用户
发布于 2010-06-09 07:25:47
如果你看一下列表框的模板，它只是一个滚动浏览器，里面有一个项目管理器。您需要计算项目的大小，并使用scroll horizontally或vertically在滚动查看器中定位项目。4月silverlight工具包有一个扩展方法GetScrollHost，您可以在列表框上调用它来获取底层的滚动查看器。
一旦有了它，你就可以使用当前的Horizontal或Vertical偏移量作为参考框架，并相应地移动你的列表。
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原文链接：
https://stackoverflow.com/questions/2946954
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