如何创建自动滚动文本框 [英] How do I create an Autoscrolling TextBox

问题描述

我有一个 WPF 应用程序，其中包含一个用于显示调试文本输出的多行 TextBox.

I have a WPF application that contains a multiline TextBox that is being used to display debugging text output.

如何设置文本框，以便在文本附加到文本框时，它会自动滚动到文本框的底部?

How can I set the TextBox so that as text is appended to the box, it will automatically scroll to the bottom of the textbox?

• 我使用的是 MVVM 模式.
• 理想情况下，纯 XAML 方法会很好.
• TextBox 本身不一定是焦点.

推荐答案

@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.

The answer provided by @BojinLi works well. After reading through the answer linked to by @GazTheDestroyer however, I decided to implement my own version for the TextBox, because it looked cleaner.

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)

To summarize, you can extend the behavior of the TextBox control by using an attached property. (Called ScrollOnTextChanged)

使用起来很简单:

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

这是 TextBoxBehaviour 类:

Here is the TextBoxBehaviour class:

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;
            }
        }

    }
}

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