27

我有一个 WPF 应用程序，其中包含一个多行文本框，用于显示调试文本输出。

如何设置 TextBox 以便将文本附加到框中时，它会自动滚动到文本框的底部？

  • 我正在使用 MVVM 模式。
  • 理想情况下，纯 XAML 方法会很好。
  • TextBox 本身不一定是焦点。
4

6 回答 6

47

@BojinLi 提供的答案效果很好。然而，在阅读了@GazTheDestroyer 链接的答案后，我决定为 TextBox 实现我自己的版本，因为它看起来更干净。

总而言之，您可以通过使用附加属性来扩展 TextBox 控件的行为。（称为 ScrollOnTextChanged）

使用它很简单：

<TextBox src:TextBoxBehaviour.ScrollOnTextChanged="True" VerticalScrollBarVisibility="Auto" />

这是 TextBoxBehaviour 类：

using System;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;

namespace MyNamespace
{
    public class TextBoxBehaviour
    {
        static readonly Dictionary<TextBox, Capture> _associations = new Dictionary<TextBox, Capture>();

        public static bool GetScrollOnTextChanged(DependencyObject dependencyObject)
        {
            return (bool)dependencyObject.GetValue(ScrollOnTextChangedProperty);
        }

        public static void SetScrollOnTextChanged(DependencyObject dependencyObject, bool value)
        {
            dependencyObject.SetValue(ScrollOnTextChangedProperty, value);
        }

        public static readonly DependencyProperty ScrollOnTextChangedProperty =
            DependencyProperty.RegisterAttached("ScrollOnTextChanged", typeof (bool), typeof (TextBoxBehaviour), new UIPropertyMetadata(false, OnScrollOnTextChanged));

        static void OnScrollOnTextChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)
        {
            var textBox = dependencyObject as TextBox;
            if (textBox == null)
            {
                return;
            }
            bool oldValue = (bool) e.OldValue, newValue = (bool) e.NewValue;
            if (newValue == oldValue)
            {
                return;
            }
            if (newValue)
            {
                textBox.Loaded += TextBoxLoaded;
                textBox.Unloaded += TextBoxUnloaded;
            }
            else
            {
                textBox.Loaded -= TextBoxLoaded;
                textBox.Unloaded -= TextBoxUnloaded;
                if (_associations.ContainsKey(textBox))
                {
                    _associations[textBox].Dispose();
                }
            }
        }

        static void TextBoxUnloaded(object sender, RoutedEventArgs routedEventArgs)
        {
            var textBox = (TextBox) sender;
            _associations[textBox].Dispose();
            textBox.Unloaded -= TextBoxUnloaded;
        }

        static void TextBoxLoaded(object sender, RoutedEventArgs routedEventArgs)
        {
            var textBox = (TextBox) sender;
            textBox.Loaded -= TextBoxLoaded;
            _associations[textBox] = new Capture(textBox);
        }

        class Capture : IDisposable
        {
            private TextBox TextBox { get; set; }

            public Capture(TextBox textBox)
            {
                TextBox = textBox;
                TextBox.TextChanged += OnTextBoxOnTextChanged;
            }

            private void OnTextBoxOnTextChanged(object sender, TextChangedEventArgs args)
            {
                TextBox.ScrollToEnd();
            }

            public void Dispose()
            {
                TextBox.TextChanged -= OnTextBoxOnTextChanged;
            }
        }

    }
}
于 2012-04-12T21:51:18.153 回答
10

此解决方案的灵感来自Scott Ferguson 的附加属性解决方案，但避免存储内部关联字典，因此代码更短：

    using System;
    using System.Windows;
    using System.Windows.Controls;

    namespace AttachedPropertyTest
    {
        public static class TextBoxUtilities
        {
            public static readonly DependencyProperty AlwaysScrollToEndProperty = DependencyProperty.RegisterAttached("AlwaysScrollToEnd",
                                                                                                                      typeof(bool),
                                                                                                                      typeof(TextBoxUtilities),
                                                                                                                      new PropertyMetadata(false, AlwaysScrollToEndChanged));

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

            public static bool GetAlwaysScrollToEnd(TextBox textBox)
            {
                if (textBox == null) {
                    throw new ArgumentNullException("textBox");
                }

                return (bool)textBox.GetValue(AlwaysScrollToEndProperty);
            }

            public static void SetAlwaysScrollToEnd(TextBox textBox, bool alwaysScrollToEnd)
            {
                if (textBox == null) {
                    throw new ArgumentNullException("textBox");
                }

                textBox.SetValue(AlwaysScrollToEndProperty, alwaysScrollToEnd);
            }

            private static void TextChanged(object sender, TextChangedEventArgs e)
            {
                ((TextBox)sender).ScrollToEnd();
            }
        }
    }

据我所知，它的行为完全符合预期。这是一个测试用例，窗口中有几个文本框，允许AlwaysScrollToEnd以各种方式设置附加属性（硬编码、CheckBox.IsChecked绑定和代码隐藏）：

xml:

    <Window x:Class="AttachedPropertyTest.Window1"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="AttachedPropertyTest" Height="800" Width="300"
        xmlns:local="clr-namespace:AttachedPropertyTest">
        <Window.Resources>
            <Style x:Key="MultiLineTB" TargetType="TextBox">
                <Setter Property="IsReadOnly" Value="True"/>
                <Setter Property="VerticalScrollBarVisibility" Value="Auto"/>
                <Setter Property="Height" Value="60"/>
                <Setter Property="Text" Value="{Binding Text, ElementName=tbMaster}"/>
            </Style>
        </Window.Resources>

        <Grid>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="Auto"/>
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
                <RowDefinition Height="Auto"/>
            </Grid.RowDefinitions>

            <TextBox Background="LightYellow" Name="tbMaster" Height="150" AcceptsReturn="True"/>

            <TextBox Style="{StaticResource MultiLineTB}" Grid.Row="1" local:TextBoxUtilities.AlwaysScrollToEnd="True"/>
            <TextBox Style="{StaticResource MultiLineTB}" Grid.Row="2"/>
            <TextBox Style="{StaticResource MultiLineTB}" Grid.Row="3" Name="tb3" local:TextBoxUtilities.AlwaysScrollToEnd="True"/>
            <TextBox Style="{StaticResource MultiLineTB}" Grid.Row="4" Name="tb4"/>
            <CheckBox Grid.Column="1" Grid.Row="4" IsChecked="{Binding (local:TextBoxUtilities.AlwaysScrollToEnd), Mode=TwoWay, ElementName=tb4}"/>
            <Button Grid.Row="5" Click="Button_Click"/>
        </Grid>
    </Window>

代码隐藏：

    using System;
    using System.Windows;
    using System.Windows.Controls;

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

            void Button_Click(object sender, RoutedEventArgs e)
            {
                TextBoxUtilities.SetAlwaysScrollToEnd(tb3, true);
            }
        }
    }
于 2012-09-10T06:44:46.697 回答
4

嗯，这似乎是一件有趣的事情，所以我尝试了一下。从一些凝视来看，似乎没有一种直接的方法可以“告诉”文本框将自身滚动到最后。所以我换了个思路。WPF 中的所有框架控件都有一个默认的 Style/ControlTemplate，从 Textbox 控件的外观判断，其中必须有一个 ScrollViewer 来处理滚动。那么，为什么不直接使用默认文本框 ControlTemplate 的本地副本并以编程方式获取 ScrollViewer。然后我可以告诉 ScrollViewer 将其内容滚动到最后。事实证明这个想法有效。

这是我编写的测试程序，可以使用一些重构，但您可以通过查看它来了解它：

这是 XAML：

<Window x:Class="WpfApplication3.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:WpfApplication3="clr-namespace:WpfApplication3"
        Title="MainWindow" Height="350" Width="525">
  <Window.Resources>
    <!--The default Style for the Framework Textbox-->
    <SolidColorBrush x:Key="DisabledForegroundBrush" Color="#888" />
    <SolidColorBrush x:Key="DisabledBackgroundBrush" Color="#EEE" />
    <SolidColorBrush x:Key="WindowBackgroundBrush" Color="#FFF" />
    <SolidColorBrush x:Key="SolidBorderBrush" Color="#888" />
    <ControlTemplate x:Key="MyTextBoxTemplate" TargetType="{x:Type TextBoxBase}">
      <Border x:Name="Border" CornerRadius="2" Padding="2" Background="{StaticResource WindowBackgroundBrush}"
              BorderBrush="{StaticResource SolidBorderBrush}" BorderThickness="1">
        <ScrollViewer Margin="0" x:Name="PART_ContentHost" />
      </Border>
      <ControlTemplate.Triggers>
        <Trigger Property="IsEnabled" Value="False">
          <Setter TargetName="Border" Property="Background" Value="{StaticResource DisabledBackgroundBrush}" />
          <Setter TargetName="Border" Property="BorderBrush" Value="{StaticResource DisabledBackgroundBrush}" />
          <Setter Property="Foreground" Value="{StaticResource DisabledForegroundBrush}" />
        </Trigger>
      </ControlTemplate.Triggers>
    </ControlTemplate>
    <Style x:Key="MyTextBox" TargetType="{x:Type TextBoxBase}">
      <Setter Property="SnapsToDevicePixels" Value="True" />
      <Setter Property="OverridesDefaultStyle" Value="True" />
      <Setter Property="KeyboardNavigation.TabNavigation" Value="None" />
      <Setter Property="FocusVisualStyle" Value="{x:Null}" />
      <Setter Property="MinWidth" Value="120" />
      <Setter Property="MinHeight" Value="20" />
      <Setter Property="AllowDrop" Value="true" />
      <Setter Property="Template" Value="{StaticResource MyTextBoxTemplate}"></Setter>
    </Style>

  </Window.Resources>
  <Grid>
    <WpfApplication3:AutoScrollTextBox x:Name="textbox" TextWrapping="Wrap" Style="{StaticResource MyTextBox}"
                                       VerticalScrollBarVisibility="Visible" AcceptsReturn="True" Width="100" Height="100">test</WpfApplication3:AutoScrollTextBox>
  </Grid>
</Window>

以及背后的代码：

using System;
using System.Windows;
using System.Windows.Controls;

namespace WpfApplication3
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            for (int i = 0; i < 10; i++)
            {
                textbox.AppendText("Line " + i + Environment.NewLine);
            }
        }
    }

    public class AutoScrollTextBox : TextBox
    {
        protected override void OnTextChanged(TextChangedEventArgs e)
        {
            base.OnTextChanged(e);
            // Make sure the Template is in the Visual Tree: 
            // http://stackoverflow.com/questions/2285491/wpf-findname-returns-null-when-it-should-not
            ApplyTemplate();
            var template = (ControlTemplate) FindResource("MyTextBoxTemplate");
            var scrollViewer = template.FindName("PART_ContentHost", this) as ScrollViewer;
            //SelectionStart = Text.Length;
            scrollViewer.ScrollToEnd();
        }
    }
}
于 2012-04-11T04:39:33.037 回答
3

一种更便携的方法可能是使用附加属性，例如在listbox 的类似问题中。

（属性变化VerticalOffset时才设置）Text

于 2012-04-11T08:41:47.423 回答
3

与其他答案类似，但没有静态事件和控制字典。（恕我直言，如果可能，最好避免静态事件）。

public class ScrollToEndBehavior
{
    public static readonly DependencyProperty OnTextChangedProperty =
                DependencyProperty.RegisterAttached(
                "OnTextChanged",
                typeof(bool),
                typeof(ScrollToEndBehavior),
                new UIPropertyMetadata(false, OnTextChanged)
                );

    public static bool GetOnTextChanged(DependencyObject dependencyObject)
    {
        return (bool)dependencyObject.GetValue(OnTextChangedProperty);
    }

    public static void SetOnTextChanged(DependencyObject dependencyObject, bool value)
    {
        dependencyObject.SetValue(OnTextChangedProperty, value);
    }

    private static void OnTextChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)
    {
        var textBox = dependencyObject as TextBox;
        var newValue = (bool)e.NewValue;

        if (textBox == null || (bool)e.OldValue == newValue)
        {
            return;
        }

        TextChangedEventHandler handler = (object sender, TextChangedEventArgs args) =>
            ((TextBox)sender).ScrollToEnd();

        if (newValue)
        {
            textBox.TextChanged += handler;
        }
        else
        {
            textBox.TextChanged -= handler;
        }
    }
}

这只是其他已发布解决方案的替代方案，这些解决方案是我在寻找一段时间后发现的最好的解决方案之一（即简洁和 mvvm）。

于 2014-06-02T23:31:47.733 回答
1

“ScrollToEnd”方法的问题是 TextBox 必须是可见的，否则它不会滚动。

因此，更好的方法是将 TextBox Selection 属性设置为文档结尾：

  static void tb_TextChanged(object sender, TextChangedEventArgs e)
  {
     TextBox tb = sender as TextBox;
     if (tb == null)
     {
        return;
     }

     // set selection to end of document
     tb.SelectionStart = int.MaxValue;
     tb.SelectionLength = 0;         
  }

顺便说一句，第一个示例中的内存泄漏处理可能是不必要的。TextBox 是发布者，静态附加属性事件处理程序是订阅者。发布者保留对订阅者的引用，这可以使订阅者保持活动状态（而不是相反。）因此，如果 TextBox 超出范围，对静态事件处理程序的引用也会如此（即，没有内存泄漏。）

所以连接附加属性可以更简单地处理：

  static void OnAutoTextScrollChanged
      (DependencyObject obj, DependencyPropertyChangedEventArgs args)
  {
     TextBox tb = obj as TextBox;
     if (tb == null)
     {
        return;
     }

     bool b = (bool)args.NewValue;

     if (b)
     {
        tb.TextChanged += tb_TextChanged;
     }
     else
     {
        tb.TextChanged -= tb_TextChanged;
     }
  }
于 2013-08-24T06:26:42.160 回答