Question

我有一个简单的TextBox：

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

从codebehind我每次都添加一些文字：

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";
}

当我点击文本框时，当我向其添加一些文字时，它会自动将滚动条置于顶部。

如果我像这样处理PreviewMouseLeftButtonDown事件：

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

文本框工作正常但我不能（当然）选择任何文本。

任何阻止此行为的想法？

编辑1：我注意到在创建文本框时，即使它已经有焦点，也没有任何插入符号。插入符号仅在执行单击时显示，但在单击后无法找到文本框内的更改内容。我的TextBox是只读的，因此我不需要插入符号。

Answer 1

5月：PART_txtBx.CaretIndex =PART_txtBx.Length;

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

ScrollToEnd(). 使用textbox_changed事件

Answer 2

您需要扩展TextBox控件以添加PreviewTextChanged事件，就像描述here一样。在PreviewTextChanged上，您必须记住SelectionStart和SelectionLength

处理TextBox的事件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;
}

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
}

如果输入手动文本，则必须阻止文本选择

希望，这有帮助

Answer 3

So i created my own CustomTextblock for resolving this issue:

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;
        }
    }
}

this CustomTextBox also pin the scrollbar to the bottom when i manually put it to bottom. the xaml:

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

Sadly with this implementation selection is broken. I'll look into it

当我点击它时，文本框引脚顶部

3 个答案: