Question

我想在包裹ScrollViewer的{{1}}中创建以下行为：
当ContentControl高度增加时，ContentControl应自动滚动到结尾。使用ScrollViewer很容易实现这一点。
但是，如果用户使用滚动条，则不应再进行自动滚动。这与VS输出窗口中发生的情况类似。

问题是要知道由于用户滚动而发生滚动的时间以及因为内容大小发生变化而发生滚动的时间。我尝试使用ScrollViewer.ScrollToEnd() ScrollChangedEventArgs，但无法使其发挥作用。

理想情况下，我不想处理所有可能的鼠标和键盘事件。

Answer 1

您可以使用ScrollChangedEventArgs.ExtentHeightChange来了解ScrollChanged是由于内容更改还是用户操作... 当内容不变时，ScrollBar位置设置或取消设置自动滚动模式。内容更改后，您可以应用自动滚动。

代码背后：

    private Boolean AutoScroll = true;

    private void ScrollViewer_ScrollChanged(Object sender, ScrollChangedEventArgs e)
    {
        // User scroll event : set or unset auto-scroll mode
        if (e.ExtentHeightChange == 0)
        {   // Content unchanged : user scroll event
            if (ScrollViewer.VerticalOffset == ScrollViewer.ScrollableHeight)
            {   // Scroll bar is in bottom
                // Set auto-scroll mode
                AutoScroll = true;
            }
            else
            {   // Scroll bar isn't in bottom
                // Unset auto-scroll mode
                AutoScroll = false;
            }
        }

        // Content scroll event : auto-scroll eventually
        if (AutoScroll && e.ExtentHeightChange != 0)
        {   // Content changed and auto-scroll mode set
            // Autoscroll
            ScrollViewer.ScrollToVerticalOffset(ScrollViewer.ExtentHeight);
        }
    }

Answer 2

以下是来自多个来源的改编。

public class ScrollViewerExtensions
    {
        public static readonly DependencyProperty AlwaysScrollToEndProperty = DependencyProperty.RegisterAttached("AlwaysScrollToEnd", typeof(bool), typeof(ScrollViewerExtensions), new PropertyMetadata(false, AlwaysScrollToEndChanged));
        private static bool _autoScroll;

        private static void AlwaysScrollToEndChanged(object sender, DependencyPropertyChangedEventArgs e)
        {
            ScrollViewer scroll = sender as ScrollViewer;
            if (scroll != null)
            {
                bool alwaysScrollToEnd = (e.NewValue != null) && (bool)e.NewValue;
                if (alwaysScrollToEnd)
                {
                    scroll.ScrollToEnd();
                    scroll.ScrollChanged += ScrollChanged;
                }
                else { scroll.ScrollChanged -= ScrollChanged; }
            }
            else { throw new InvalidOperationException("The attached AlwaysScrollToEnd property can only be applied to ScrollViewer instances."); }
        }

        public static bool GetAlwaysScrollToEnd(ScrollViewer scroll)
        {
            if (scroll == null) { throw new ArgumentNullException("scroll"); }
            return (bool)scroll.GetValue(AlwaysScrollToEndProperty);
        }

        public static void SetAlwaysScrollToEnd(ScrollViewer scroll, bool alwaysScrollToEnd)
        {
            if (scroll == null) { throw new ArgumentNullException("scroll"); }
            scroll.SetValue(AlwaysScrollToEndProperty, alwaysScrollToEnd);
        }

        private static void ScrollChanged(object sender, ScrollChangedEventArgs e)
        {
            ScrollViewer scroll = sender as ScrollViewer;
            if (scroll == null) { throw new InvalidOperationException("The attached AlwaysScrollToEnd property can only be applied to ScrollViewer instances."); }

            // User scroll event : set or unset autoscroll mode
            if (e.ExtentHeightChange == 0) { _autoScroll = scroll.VerticalOffset == scroll.ScrollableHeight; }

            // Content scroll event : autoscroll eventually
            if (_autoScroll && e.ExtentHeightChange != 0) { scroll.ScrollToVerticalOffset(scroll.ExtentHeight); }
        }
    }

在您的XAML中使用它，如下所示：

<ScrollViewer Height="230" HorizontalScrollBarVisibility="Auto" extensionProperties:ScrollViewerExtension.AlwaysScrollToEnd="True">
    <TextBlock x:Name="Trace"/>
</ScrollViewer>

Answer 3

如果以前完全滚动内容，此代码将自动滚动到内容增长时结束。

XAML：

<Window x:Class="AutoScrollTest.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Height="300" Width="300">
    <ScrollViewer Name="_scrollViewer">
        <Border BorderBrush="Red" BorderThickness="5" Name="_contentCtrl" Height="200" VerticalAlignment="Top">
        </Border>
    </ScrollViewer>
</Window>

代码背后：

using System;
using System.Windows;
using System.Windows.Threading;

namespace AutoScrollTest
{
    public partial class Window1 : Window
    {
        public Window1()
        {
            InitializeComponent();

            DispatcherTimer timer = new DispatcherTimer();
            timer.Interval = new TimeSpan(0, 0, 2);
            timer.Tick += ((sender, e) =>
                {
                    _contentCtrl.Height += 10;

                    if (_scrollViewer.VerticalOffset == _scrollViewer.ScrollableHeight)
                    {
                        _scrollViewer.ScrollToEnd();
                    }
                });
            timer.Start();
        }
    }
}

Answer 4

这是我使用的方法，效果很好。基于两个依赖属性。它避免了代码隐藏和定时器，如另一个答案中所示。

public static class ScrollViewerEx
{
    public static readonly DependencyProperty AutoScrollProperty =
        DependencyProperty.RegisterAttached("AutoScrollToEnd", 
            typeof(bool), typeof(ScrollViewerEx), 
            new PropertyMetadata(false, HookupAutoScrollToEnd));

    public static readonly DependencyProperty AutoScrollHandlerProperty =
        DependencyProperty.RegisterAttached("AutoScrollToEndHandler", 
            typeof(ScrollViewerAutoScrollToEndHandler), typeof(ScrollViewerEx));

    private static void HookupAutoScrollToEnd(DependencyObject d, 
            DependencyPropertyChangedEventArgs e)
    {
        var scrollViewer = d as ScrollViewer;
        if (scrollViewer == null) return;

        SetAutoScrollToEnd(scrollViewer, (bool)e.NewValue);
    }

    public static bool GetAutoScrollToEnd(ScrollViewer instance)
    {
        return (bool)instance.GetValue(AutoScrollProperty);
    }

    public static void SetAutoScrollToEnd(ScrollViewer instance, bool value)
    {
        var oldHandler = (ScrollViewerAutoScrollToEndHandler)instance.GetValue(AutoScrollHandlerProperty);
        if (oldHandler != null)
        {
            oldHandler.Dispose();
            instance.SetValue(AutoScrollHandlerProperty, null);
        }
        instance.SetValue(AutoScrollProperty, value);
        if (value)
            instance.SetValue(AutoScrollHandlerProperty, new ScrollViewerAutoScrollToEndHandler(instance));
    }

这使用定义为。

的处理程序

public class ScrollViewerAutoScrollToEndHandler : DependencyObject, IDisposable
{
    readonly ScrollViewer m_scrollViewer;
    bool m_doScroll = false;

    public ScrollViewerAutoScrollToEndHandler(ScrollViewer scrollViewer)
    {
        if (scrollViewer == null) { throw new ArgumentNullException("scrollViewer"); }

        m_scrollViewer = scrollViewer;
        m_scrollViewer.ScrollToEnd();
        m_scrollViewer.ScrollChanged += ScrollChanged;
    }

    private void ScrollChanged(object sender, ScrollChangedEventArgs e)
    {
        // User scroll event : set or unset autoscroll mode
        if (e.ExtentHeightChange == 0) 
        { m_doScroll = m_scrollViewer.VerticalOffset == m_scrollViewer.ScrollableHeight; }

        // Content scroll event : autoscroll eventually
        if (m_doScroll && e.ExtentHeightChange != 0) 
        { m_scrollViewer.ScrollToVerticalOffset(m_scrollViewer.ExtentHeight); }
    }

    public void Dispose()
    {
        m_scrollViewer.ScrollChanged -= ScrollChanged;
    }

然后只需在XAML中使用它：

<ScrollViewer VerticalScrollBarVisibility="Auto" 
              local:ScrollViewerEx.AutoScrollToEnd="True">
    <TextBlock x:Name="Test test test"/>
</ScrollViewer>

将local作为名称空间导入位于相关XAML文件的顶部。这避免了在其他答案中看到的static bool。

Answer 5

bool autoScroll = false;

        if (e.ExtentHeightChange != 0)
        {   
            if (infoScroll.VerticalOffset == infoScroll.ScrollableHeight - e.ExtentHeightChange)
            { 
                autoScroll = true;
            }
            else
            {   
                autoScroll = false;
            }
        }
        if (autoScroll)
        {   
            infoScroll.ScrollToVerticalOffset(infoScroll.ExtentHeight);
        }

Воттаквроде-быпривельнеечемуWallstreetProgrammer

Answer 6

使用TextBox的“TextChanged”事件和ScrollToEnd（）方法怎么样？

 private void consolebox_TextChanged(object sender, TextChangedEventArgs e)
    {
        this.consolebox.ScrollToEnd();
    }

Answer 7

在Windows 10中，.ScrollToVerticalOffset已过时。所以我像这样使用 ChangeView 。

TextBlock messageBar;
ScrollViewer messageScroller; 

    private void displayMessage(string message)
    {

                messageBar.Text += message + "\n";

                double pos = this.messageScroller.ExtentHeight;
                messageScroller.ChangeView(null, pos, null);
    }

Answer 8

重写以前的答案以使用浮点比较。请注意，此解决方案虽然简单，但只要内容滚动到底部，就会阻止用户滚动。

private bool _should_auto_scroll = true;
private void ScrollViewer_OnScrollChanged(object sender, ScrollChangedEventArgs e) {
    if (Math.Abs(e.ExtentHeightChange) < float.MinValue) {
        _should_auto_scroll = Math.Abs(ScrollViewer.VerticalOffset - ScrollViewer.ScrollableHeight) < float.MinValue;
    }
    if (_should_auto_scroll && Math.Abs(e.ExtentHeightChange) > float.MinValue) {
        ScrollViewer.ScrollToVerticalOffset(ScrollViewer.ExtentHeight);
    }
}

Answer 9

在Windows版本17763和更高版本上，可以在ScrollViewer上设置VerticalAnchorRatio="1"就是这样。

方法：：仍有一个错误尚未解决：https://github.com/Microsoft/microsoft-ui-xaml/issues/562

Answer 10

基于第二个答案，为什么不能只是：

private void ScrollViewer_ScrollChanged(Object sender, ScrollChangedEventArgs e)
{
    if (e.ExtentHeightChange != 0)
    {
        ScrollViewer.ScrollToVerticalOffset(ScrollViewer.ExtentHeight);
    }
}

我已经在我的应用程序上对其进行了测试，并且可以正常工作。

如何自动滚动ScrollViewer - 仅当用户没有更改滚动位置时

10 个答案: