当我单击时，文本框固定在顶部

Question

我有一个简单的TextBox：

<TextBox Name="PART_txtBx" IsReadOnly="True" ScrollViewer.VerticalScrollBarVisibility="Auto"  />

从代码背后我每次都添加一些文本：

public MainWindow()
{
    InitializeComponent();

    DispatcherTimer dt = new DispatcherTimer();
    dt.Interval = TimeSpan.FromMilliseconds(100);
    dt.Tick += dt_Tick;
    dt.Start();
}

void dt_Tick(object sender, EventArgs e)
{
    PART_txtBx.Text += "hi\n";
}

当我单击文本框时，当我向其中添加一些文本时，它会自动将滚动条放在顶部。

如果我像这样处理PreviewMouseLeftButtonDown事件：

private void PART_txtBx_PreviewMouseLeftButtonDown_1(object sender, MouseButtonEventArgs e)
{
    e.Handled = true;
}

该文本框正常工作，但我不能（当然）选择任何文本。

有什么想法可以防止这种行为？

编辑1：我注意到创建文本框时，即使有焦点，也没有任何插入符号。 仅在执行单击时显示插入符号，但是单击后我无法在文本框中找到更改内容。 我的文本框是只读的，所以我不需要插入符号。

Answer 1

可能： PART_txtBx.CaretIndex =PART_txtBx.Length;

或： PART_txtBx.SelectionStart = PART_txtBx.Text.Length; PART_txtBx.ScrollToCaret(); PART_txtBx.SelectionStart = PART_txtBx.Text.Length; PART_txtBx.ScrollToCaret();

ScrollToEnd（）。 与textbox_changed事件

Answer 2

1. 您需要延长您的TextBox控件添加PreviewTextChanged事件，就像是描述在这里 。 在PreviewTextChanged上，您必须记住SelectionStart和SelectionLength

2. 为您的TextBox处理事件ScrollViewer.ScrollChanged：

    ScrollViewer.ScrollChanged="OnScrollChanged" <!--in xaml--> private void OnScrollChanged(object sender, ScrollChangedEventArgs e) { // here you could prevent scrolling isOnBottom = (sender as TextBox).VerticalOffset + (sender as TextBox).ViewportHeight == (sender as TextBox).ExtentHeight; } 

3. 处理TextChanged事件：

    TextChanged="OnTextChanged" private void OnTextChanged(object sender, TextChangedEventArgs e) { if (isOnBottom) (sender as TextBox).ScrollToEnd(); // and here you can select text that was selected earlier // by using remembered SelectionStart and SelectionLength } 

4. 在手动输入文本的情况下，您将不得不选择文本

希望能帮助到你

Answer 3

因此，我创建了自己的CustomTextblock来解决此问题：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;

namespace CE.EthernetMessagesManager.Views
{
    public class CustomTextBox : TextBox
    {
        private int realCaretIndex = 0;
        private bool triggeredByUser = false;
        private bool isScrollingWithMouse = false;

        public CustomTextBox()
            : base()
        {
            this.PreviewMouseLeftButtonDown += CustomTextBox_PreviewMouseLeftButtonDown;
            this.PreviewMouseLeftButtonUp += CustomTextBox_PreviewMouseLeftButtonUp;
            this.PreviewMouseMove += CustomTextBox_PreviewMouseMove;
            this.PreviewMouseWheel += CustomTextBox_PreviewMouseWheel;
            this.TextChanged += CustomTextBox_TextChanged;
            this.LostFocus += CustomTextBox_LostFocus;

            this.AddHandler(ScrollViewer.ScrollChangedEvent, new RoutedEventHandler((X, S) =>
            {
                if ((S as ScrollChangedEventArgs).VerticalChange != 0 && triggeredByUser)
                {
                    TextBox textBox = (X as TextBox);
                    int newLinePosition = 0;
                    newLinePosition = (int)(((S as ScrollChangedEventArgs).VerticalChange + textBox.ExtentHeight) / (textBox.FontSize + 2));

                    realCaretIndex += newLinePosition * ((S as ScrollChangedEventArgs).VerticalChange < 0 ? -1 : 1);
                    if (realCaretIndex < 0)
                        realCaretIndex = 0;

                    textBox.CaretIndex = realCaretIndex;
                    triggeredByUser = false;
                }
            }));
        }

        void CustomTextBox_LostFocus(object sender, System.Windows.RoutedEventArgs e)
        {
            e.Handled = true;
        }

        void CustomTextBox_TextChanged(object sender, TextChangedEventArgs e)
        {
            TextBox textBox = sender as TextBox;
            textBox.CaretIndex = realCaretIndex;

            var max = (textBox.ExtentHeight - textBox.ViewportHeight);
            var offset = textBox.VerticalOffset;

            if (max != 0 && max == offset)
                this.Dispatcher.Invoke(new Action(() =>
                {
                    textBox.ScrollToEnd();
                }),
                    System.Windows.Threading.DispatcherPriority.Loaded);
        }

        void CustomTextBox_PreviewMouseWheel(object sender, System.Windows.Input.MouseWheelEventArgs e)
        {
            triggeredByUser = true;
        }

        void CustomTextBox_PreviewMouseMove(object sender, System.Windows.Input.MouseEventArgs e)
        {
            if (isScrollingWithMouse)
            {
                TextBox textBox = sender as TextBox;
                realCaretIndex = textBox.GetCharacterIndexFromPoint(Mouse.GetPosition(textBox), true);
            }
        }

        void CustomTextBox_PreviewMouseLeftButtonUp(object sender, System.Windows.Input.MouseButtonEventArgs e)
        {
            isScrollingWithMouse = false;
        }

        void CustomTextBox_PreviewMouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
        {
            TextBox textBox = sender as TextBox;
            realCaretIndex = textBox.GetCharacterIndexFromPoint(Mouse.GetPosition(textBox), true);
            triggeredByUser = true;
            isScrollingWithMouse = true;
        }
    }
}

当我手动将其滚动到底部时，此CustomTextBox还将滚动条固定在底部。 xaml：

            <v:CustomTextBox 
                IsReadOnly="True"
                ScrollViewer.HorizontalScrollBarVisibility="Auto"
                ScrollViewer.VerticalScrollBarVisibility="Auto"
                />

遗憾的是，此实现选择被打破了。 我会调查一下