WPF ListBox 自动滚动到结束

Question

在我的应用程序中，我有一个带有项目的ListBox。该应用程序是用 WPF 编写的。

如何自动滚动到最后添加的项目？我希望在添加新项目后将 ScrollViewer 移到列表末尾。

有像ItemsChanged这样的活动吗？ （我不想使用SelectionChanged 事件）

Answer 1

试试这个：

lstBox.SelectedIndex = lstBox.Items.Count -1;
lstBox.ScrollIntoView(lstBox.SelectedItem) ;

在您的 MainWindow 中，这将选择并关注列表中的最后一项！

Answer 2

最简单的方法：

if (VisualTreeHelper.GetChildrenCount(listView) > 0)
{
    Border border = (Border)VisualTreeHelper.GetChild(listView, 0);
    ScrollViewer scrollViewer = (ScrollViewer)VisualTreeHelper.GetChild(border, 0);
    scrollViewer.ScrollToBottom();
}

它始终适用于 ListView 和 ListBox 控件。将此代码附加到listView.Items.SourceCollection.CollectionChanged 事件中，您将拥有全自动的自动滚动行为。

Answer 3

请记住，listBox.ScrollIntoView(listBox.Items[listBox.Items.Count - 1]); 仅在您没有重复项时才有效。如果您有具有相同内容的项目，它会向下滚动到第一个查找。

这是我找到的解决方案：

ListBoxAutomationPeer svAutomation = (ListBoxAutomationPeer)ScrollViewerAutomationPeer.CreatePeerForElement(myListBox);

IScrollProvider scrollInterface = (IScrollProvider)svAutomation.GetPattern(PatternInterface.Scroll);
System.Windows.Automation.ScrollAmount scrollVertical = System.Windows.Automation.ScrollAmount.LargeIncrement;
System.Windows.Automation.ScrollAmount scrollHorizontal = System.Windows.Automation.ScrollAmount.NoAmount;
//If the vertical scroller is not available, the operation cannot be performed, which will raise an exception. 
if ( scrollInterface.VerticallyScrollable )
    scrollInterface.Scroll(scrollHorizontal, scrollVertical);

Answer 4

最好的解决方案是使用 ListBox 控件内的 ItemCollection 对象 这个系列是专门为内容观众设计的。它有一个预定义的方法来选择最后一项并保持光标位置参考......

myListBox.Items.MoveCurrentToLast();
myListBox.ScrollIntoView(myListBox.Items.CurrentItem);

Answer 5

与目前介绍的方法略有不同。

您可以使用ScrollViewer ScrollChanged 事件并观察ScrollViewer 的内容是否变大。

private void ListBox_OnLoaded(object sender, RoutedEventArgs e)
{
    var listBox = (ListBox) sender;

    var scrollViewer = FindScrollViewer(listBox);

    if (scrollViewer != null)
    {
        scrollViewer.ScrollChanged += (o, args) =>
        {
            if (args.ExtentHeightChange > 0)
                scrollViewer.ScrollToBottom();
        };
    }
}

这避免了绑定到 ListBox ItemsSource 更改的一些问题。

ScrollViewer 也可以在不假设 ListBox 使用默认控件模板的情况下找到。

// Search for ScrollViewer, breadth-first
private static ScrollViewer FindScrollViewer(DependencyObject root)
{
    var queue = new Queue<DependencyObject>(new[] {root});

    do
    {
        var item = queue.Dequeue();

        if (item is ScrollViewer)
            return (ScrollViewer) item;

        for (var i = 0; i < VisualTreeHelper.GetChildrenCount(item); i++)
            queue.Enqueue(VisualTreeHelper.GetChild(item, i));
    } while (queue.Count > 0);

    return null;
}

然后将此附加到ListBox Loaded 事件：

<ListBox Loaded="ListBox_OnLoaded" />

这可以很容易地修改为附加属性，使其更通用。

---

或者yarik的建议：

<ListBox ScrollViewer.ScrollChanged="ScrollViewer_OnScrollChanged" />

在后面的代码中：

private void ScrollViewer_OnScrollChanged(object sender, ScrollChangedEventArgs e)
{
    if (e.OriginalSource is ScrollViewer scrollViewer &&
        Math.Abs(e.ExtentHeightChange) > 0.0)
    {
        scrollViewer.ScrollToBottom();
    }
}

Answer 6

listBox.ScrollIntoView(listBox.Items[listBox.Items.Count - 1]);

Answer 7

这里的答案都没有满足我的需要。因此，我编写了自己的行为，即自动滚动项目控件，并在用户向上滚动时暂停自动滚动，并在用户向下滚动到底部时恢复自动滚动。

/// <summary>
/// This will auto scroll a list view to the bottom as items are added.
/// Automatically suspends if the user scrolls up, and recommences when
/// the user scrolls to the end.
/// </summary>
/// <example>
///     <ListView sf:AutoScrollToBottomBehavior="{Binding viewModelAutoScrollFlag}" />
/// </example>
public class AutoScrollToBottomBehavior
{
  /// <summary>
  /// Enumerated type to keep track of the current auto scroll status
  /// </summary>
  public enum StatusType
  {
    NotAutoScrollingToBottom,
    AutoScrollingToBottom,
    AutoScrollingToBottomButSuppressed
  }

  public static StatusType GetAutoScrollToBottomStatus(DependencyObject obj)
  {
    return (StatusType)obj.GetValue(AutoScrollToBottomStatusProperty);
  }

  public static void SetAutoScrollToBottomStatus(DependencyObject obj, StatusType value)
  {
    obj.SetValue(AutoScrollToBottomStatusProperty, value);
  }

  // Using a DependencyProperty as the backing store for AutoScrollToBottomStatus.  This enables animation, styling, binding, etc...
  public static readonly DependencyProperty AutoScrollToBottomStatusProperty =
      DependencyProperty.RegisterAttached(
        "AutoScrollToBottomStatus",
        typeof(StatusType),
        typeof(AutoScrollToBottomBehavior),
        new PropertyMetadata(StatusType.NotAutoScrollingToBottom, (s, e) =>
        {
          if (s is DependencyObject viewer && e.NewValue is StatusType autoScrollToBottomStatus)
          {
            // Set the AutoScrollToBottom property to mirror this one

            bool? autoScrollToBottom = autoScrollToBottomStatus switch
            {
              StatusType.AutoScrollingToBottom => true,
              StatusType.NotAutoScrollingToBottom => false,
              StatusType.AutoScrollingToBottomButSuppressed => false,
              _ => null
            };

            if (autoScrollToBottom.HasValue)
            {
              SetAutoScrollToBottom(viewer, autoScrollToBottom.Value);
            }

            // Only hook/unhook for cases below, not when suspended
            switch(autoScrollToBottomStatus)
            {
              case StatusType.AutoScrollingToBottom:
                HookViewer(viewer);
                break;
              case StatusType.NotAutoScrollingToBottom:
                UnhookViewer(viewer);
                break;
            }
          }
        }));


  public static bool GetAutoScrollToBottom(DependencyObject obj)
  {
    return (bool)obj.GetValue(AutoScrollToBottomProperty);
  }

  public static void SetAutoScrollToBottom(DependencyObject obj, bool value)
  {
    obj.SetValue(AutoScrollToBottomProperty, value);
  }

  // Using a DependencyProperty as the backing store for AutoScrollToBottom.  This enables animation, styling, binding, etc...
  public static readonly DependencyProperty AutoScrollToBottomProperty =
      DependencyProperty.RegisterAttached(
        "AutoScrollToBottom",
        typeof(bool),
        typeof(AutoScrollToBottomBehavior),
        new FrameworkPropertyMetadata(false,  FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, (s, e) =>
        {
          if (s is DependencyObject viewer && e.NewValue is bool autoScrollToBottom)
          {
            // Set the AutoScrollToBottomStatus property to mirror this one
            if (autoScrollToBottom)
            {
              SetAutoScrollToBottomStatus(viewer, StatusType.AutoScrollingToBottom);
            }
            else if (GetAutoScrollToBottomStatus(viewer) == StatusType.AutoScrollingToBottom)
            {
              SetAutoScrollToBottomStatus(viewer, StatusType.NotAutoScrollingToBottom);
            }

            // No change if autoScrollToBottom = false && viewer.AutoScrollToBottomStatus = AutoScrollToBottomStatusType.AutoScrollingToBottomButSuppressed;
          }
        }));


  private static Action GetUnhookAction(DependencyObject obj)
  {
    return (Action)obj.GetValue(UnhookActionProperty);
  }

  private static void SetUnhookAction(DependencyObject obj, Action value)
  {
    obj.SetValue(UnhookActionProperty, value);
  }

  // Using a DependencyProperty as the backing store for MyProperty.  This enables animation, styling, binding, etc...
  private static readonly DependencyProperty UnhookActionProperty =
      DependencyProperty.RegisterAttached("UnhookAction", typeof(Action), typeof(AutoScrollToBottomBehavior), new PropertyMetadata(null));

  private static void ItemsControl_Loaded(object sender, RoutedEventArgs e)
  {
    if (sender is ItemsControl itemsControl)
    {
      itemsControl.Loaded -= ItemsControl_Loaded;
      HookViewer(itemsControl);
    }
  }

  private static void HookViewer(DependencyObject viewer)
  {
    if (viewer is ItemsControl itemsControl)
    {
      // If this is triggered the xaml setup then the control won't be loaded yet,
      // and so won't have a visual tree which we need to get the scrollviewer,
      // so defer this hooking until the items control is loaded.
      if (!itemsControl.IsLoaded)
      {
        itemsControl.Loaded += ItemsControl_Loaded;
        return;
      }

      if (FindScrollViewer(viewer) is ScrollViewer scrollViewer)
      {
        scrollViewer.ScrollToBottom();

        // Scroll to bottom when the item count changes
        NotifyCollectionChangedEventHandler itemsCollectionChangedHandler = (s, e) =>
        {
          if (GetAutoScrollToBottom(viewer))
          {
            scrollViewer.ScrollToBottom();
          }
        };
        ((INotifyCollectionChanged)itemsControl.Items).CollectionChanged += itemsCollectionChangedHandler;


        ScrollChangedEventHandler scrollChangedEventHandler = (s, e) =>
        {
          bool userScrolledToBottom = (e.VerticalOffset + e.ViewportHeight) > (e.ExtentHeight - 1.0);
          bool userScrolledUp = e.VerticalChange < 0;

          // Check if auto scrolling should be suppressed
          if (userScrolledUp && !userScrolledToBottom)
          {
            if (GetAutoScrollToBottomStatus(viewer) == StatusType.AutoScrollingToBottom)
            {
              SetAutoScrollToBottomStatus(viewer, StatusType.AutoScrollingToBottomButSuppressed);
            }
          }

          // Check if auto scrolling should be unsuppressed
          if (userScrolledToBottom)
          {
            if (GetAutoScrollToBottomStatus(viewer) == StatusType.AutoScrollingToBottomButSuppressed)
            {
              SetAutoScrollToBottomStatus(viewer, StatusType.AutoScrollingToBottom);
            }
          }
        };

        scrollViewer.ScrollChanged += scrollChangedEventHandler;

        Action unhookAction = () =>
        {
          ((INotifyCollectionChanged)itemsControl.Items).CollectionChanged -= itemsCollectionChangedHandler;
          scrollViewer.ScrollChanged -= scrollChangedEventHandler;
        };

        SetUnhookAction(viewer, unhookAction);
      }
    }
  }

  /// <summary>
  /// Unsubscribes the event listeners on the ItemsControl and ScrollViewer
  /// </summary>
  /// <param name="viewer"></param>
  private static void UnhookViewer(DependencyObject viewer)
  {
    var unhookAction = GetUnhookAction(viewer);
    SetUnhookAction(viewer, null);
    unhookAction?.Invoke();
  }

  /// <summary>
  /// A recursive function that drills down a visual tree until a ScrollViewer is found.
  /// </summary>
  /// <param name="viewer"></param>
  /// <returns></returns>
  private static ScrollViewer FindScrollViewer(DependencyObject viewer)
  {
    if (viewer is ScrollViewer scrollViewer)
      return scrollViewer;

    return Enumerable.Range(0, VisualTreeHelper.GetChildrenCount(viewer))
      .Select(i => FindScrollViewer(VisualTreeHelper.GetChild(viewer, i)))
      .Where(child => child != null)
      .FirstOrDefault();
  }
}

Answer 8

对我来说，最简单的工作方式是这样的：（没有绑定）

 private void WriteMessage(string message, Brush color, ListView lv)
        {

            Dispatcher.BeginInvoke(new Action(delegate
            {
                ListViewItem ls = new ListViewItem
                {
                    Foreground = color,
                    Content = message
                };
                lv.Items.Add(ls);
                lv.ScrollIntoView(lv.Items[lv.Items.Count - 1]);
            }));
        }

不需要创建类或更改xaml，只需使用此方法编写消息并自动滚动。

只是调用

myLv.Items.Add(ls);
myLv.ScrollIntoView(lv.Items[lv.Items.Count - 1]);

例如，不要为我工作。

Answer 9

您可以尝试ListBox.ScrollIntoView() 方法，尽管在某些情况下有一些problems...

这是 Tamir Khason 的一个例子：Auto scroll ListBox in WPF

Answer 10

实现自动滚动最简单的方法是挂钩 CollectionChanged 事件。只需将该功能添加到派生自 ListBox 控件的自定义类：

using System.Collections.Specialized;
using System.Windows.Controls;
using System.Windows.Media;

namespace YourProgram.CustomControls
{
  public class AutoScrollListBox : ListBox
  {
      public AutoScrollListBox()
      {
          if (Items != null)
          {
              // Hook to the CollectionChanged event of your ObservableCollection
              ((INotifyCollectionChanged)Items).CollectionChanged += CollectionChange;
          }
      }

      // Is called whenever the item collection changes
      private void CollectionChange(object sender, NotifyCollectionChangedEventArgs e)
      {
          if (Items.Count > 0)
          {
              // Get the ScrollViewer object from the ListBox control
              Border border = (Border)VisualTreeHelper.GetChild(this, 0);
              ScrollViewer SV = (ScrollViewer)VisualTreeHelper.GetChild(border, 0);

              // Scroll to bottom
              SV.ScrollToBottom();
          }
      }
  }
}

将自定义控件的命名空间添加到您的 WPF 窗口并使用自定义 ListBox 控件：

<Window x:Class="MainWindow"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         xmlns:local="clr-namespace:YourProgram"
         xmlns:cc="clr-namespace:YourProgram.CustomControls"
         mc:Ignorable="d" 
         d:DesignHeight="450" d:DesignWidth="800">

    <cc:AutoScrollListBox ItemsSource="{Binding YourObservableCollection}"/>

</Window>

Answer 11

这是对我 100% 有效的方法。

初始化部分：

private ObservableCollection<ActionLogData> LogListBind = new ObservableCollection<ActionLogData>();

LogList.ItemsSource = LogListBind;
LogListBind.CollectionChanged += this.OnCollectionChanged;

绑定到我的 ObservableCollection 的 CollectionChanged 的​​委托，用作我的 ListView 的项目源：

private void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
      if (VisualTreeHelper.GetChildrenCount(LogList) > 0)
      {
           Decorator border = VisualTreeHelper.GetChild(LogList, 0) as Decorator;
           ScrollViewer scrollViewer = border.Child as ScrollViewer;
           scrollViewer.ScrollToBottom();
      }
}

此解决方案基于 @mateusz-myślak 解决方案，但我做了一些修复和简化。

Answer 12

使用 .NET 5，来自 this answer 和每个人的答案的组合，我想出的最干净的方法是：

在 View 的构造函数中订阅事件（代码隐藏）：

var listViewItemsSource = (INotifyCollectionChanged)MyListView.Items.SourceCollection;
listViewItemsSource.CollectionChanged += MyListViewCollectionChanged;

在MyListViewCollectionChanged 委托中，您获取ScrollViewer 并滚动到末尾：

private void MyListViewCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
{
    var border = (Decorator)VisualTreeHelper.GetChild(LoggerListView, 0);
    var scrollViewer = (ScrollViewer)border.Child;
    scrollViewer.ScrollToEnd();
}

注意：您无法在构造函数中获取滚动查看器，因为组件未初始化。