带预览的 C# 密码文本框
4.00/5 (4投票s)
自定义 TextBox 实现，
引言
这个自定义的 .NET Winform 文本框控件会在用户输入字符后的几毫秒内显示这些字符，然后用“星号”或其他密码字符进行遮蔽。同时允许用户编辑/插入/删除任何字符。
背景
.NET 工具箱提供的 TextBox 控件默认提供了以下选项来实现与密码相关的数据输入字段。
- PasswordChar
- UseSystemPasswordChar
然而，这些选项会在用户在文本框中输入字符时立即遮蔽这些字符。基本上，用户所看到的就是一串 '*' 字符，不确定自己即将输入什么。但是，.NET Winforms 中没有内置支持用于输入密码字符，这种支持允许我们以类似于 Android EditText 控件的方式输入任何字符。即，在用“星号”或其他密码字符遮蔽之前，先显示用户输入的字符几毫秒。并且允许用户稍后编辑/插入/删除任何字符。
使用代码
希望代码能够自解释。HidePasswordCharacters 方法负责将字符遮蔽为 '*'。每当用户键入时，文本发生变化时，都会调用此方法。
Windows 定时器在这里起着重要的作用。
- 在用户键入字符时，在文本框字段中引入一个最小的延迟。
- 执行遮蔽用户输入字符的任务。
为了实现以上两个功能，我们初始化定时器
timer = new Timer { Interval = 200 };
timer.Tick += timer_Tick;
为了引入延迟，我们将 Timer 对象的 Interval 属性设置为，例如 200 毫秒。 我们还将 timer_Tick 事件处理程序设置为执行遮蔽操作。每隔 200 毫秒会调用此事件处理程序代码，以便用户看起来字符在一定延迟后被遮蔽（这是我们的要求）。
变量 m_iCaretPosition 保存 TextBox 中任何给定时间点的更新后的光标位置。
变量 adminPassword 保存文本框字段中实际输入的文本。
免责声明：虽然在此示例中，adminPassword 的内容通过属性公开。这是为了简洁起见。在现实中，绝不应该这样做。
using System;
using System.Globalization;
using System.Text;
using System.Windows.Forms;
#region Author and File Information
/*
* Title : Custom Password Textbox with preview
* Author(s) : Srivatsa Haridas
* Version : v1.4
*/
#endregion
namespace PasswordTextbox
{
/// <summary>
///
/// </summary>
public class PasswordTextBox : TextBox
{
private readonly Timer timer;
private char[] adminPassword;
private readonly char DecimalSeparator = CultureInfo.CurrentCulture.NumberFormat.NumberDecimalSeparator.ToCharArray()[0];
private int m_iCaretPosition = 0;
private bool canEdit = true;
private const int PWD_LENGTH = 8;
/// <summary>
///
/// </summary>
public PasswordTextBox()
{
timer = new Timer { Interval = 250 };
timer.Tick += timer_Tick;
adminPassword = new Char[8];
}
/// <summary>
///
/// </summary>
public string AdminPassword
{
get
{
return new string(adminPassword).Trim('\0').Replace("\0", "");
}
}
/// <summary>
///
/// </summary>
/// <param name="e"></param>
protected override void OnTextChanged(EventArgs e)
{
if (canEdit)
{
base.OnTextChanged(e);
txtInput_TextChanged(this, e);
}
}
/// <summary>
///
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void txtInput_TextChanged(object sender, EventArgs e)
{
HidePasswordCharacters();
}
/// <summary>
///
/// </summary>
/// <param name="e"></param>
protected override void OnMouseClick(MouseEventArgs e)
{
base.OnMouseClick(e);
m_iCaretPosition = this.GetCharIndexFromPosition(e.Location);
}
/// <summary>
///
/// </summary>
private void HidePasswordCharacters()
{
int index = this.SelectionStart;
if (index > 1)
{
StringBuilder s = new StringBuilder(this.Text);
s[index - 2] = '*';
this.Text = s.ToString();
this.SelectionStart = index;
m_iCaretPosition = index;
}
timer.Enabled = true;
}
protected override void OnKeyDown(KeyEventArgs e)
{
base.OnKeyDown(e);
if (e.KeyCode == Keys.Delete)
{
canEdit = false;
DeleteSelectedCharacters(this, e.KeyCode);
}
}
/// <summary>
/// Windows Timer elapsed eventhandler
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void timer_Tick(object sender, EventArgs e)
{
timer.Enabled = false;
int index = this.SelectionStart;
if (index >= 1)
{
StringBuilder s = new StringBuilder(this.Text);
s[index - 1] = '*';
this.Invoke(new Action(() =>
{
this.Text = s.ToString();
this.SelectionStart = index;
m_iCaretPosition = index;
}));
}
}
protected override void OnKeyPress(KeyPressEventArgs e)
{
base.OnKeyPress(e);
int selectionStart = this.SelectionStart;
int length = this.TextLength;
int selectedChars = this.SelectionLength;
canEdit = false;
if (selectedChars == length)
{
/*
* Means complete text selected so clear it before using it
*/
ClearCharBufferPlusTextBox();
}
Keys eModified = (Keys)e.KeyChar;
if (e.KeyChar == DecimalSeparator)
{
e.Handled = true;
}
if ((Keys.Delete != eModified) && (Keys.Back != eModified))
{
if (Keys.Space != eModified)
{
if (e.KeyChar != '-')
{
if (!char.IsLetterOrDigit(e.KeyChar))
{
e.Handled = true;
}
else
{
if (this.TextLength < PWD_LENGTH)
{
adminPassword =
new string(adminPassword).Insert(selectionStart, e.KeyChar.ToString()).ToCharArray();
}
}
}
}
else
{
if (this.TextLength == 0)
{
e.Handled = true;
Array.Clear(adminPassword, 0, adminPassword.Length);
}
}
}
else if ((Keys.Back == eModified) || (Keys.Delete == eModified))
{
DeleteSelectedCharacters(this, eModified);
}
/*
* Replace the characters with '*'
*/
HidePasswordCharacters();
canEdit = true;
}
/// <summary>
/// Deletes the specific characters in the char array based on the key press action
/// </summary>
/// <param name="sender"></param>
private void DeleteSelectedCharacters(object sender, Keys key)
{
int selectionStart = this.SelectionStart;
int length = this.TextLength;
int selectedChars = this.SelectionLength;
if (selectedChars == length)
{
ClearCharBufferPlusTextBox();
return;
}
if (selectedChars > 0)
{
int i = selectionStart;
this.Text.Remove(selectionStart, selectedChars);
adminPassword = new string(adminPassword).Remove(selectionStart, selectedChars).ToCharArray();
}
else
{
/*
* Basically this portion of code is to handle the condition
* when the cursor is placed at the start or in the end
*/
if (selectionStart == 0)
{
/*
* Cursor in the beginning, before the first character
* Delete the character only when Del is pressed, No action when Back key is pressed
*/
if (key == Keys.Delete)
{
adminPassword = new string(adminPassword).Remove(0, 1).ToCharArray();
}
}
else if (selectionStart > 0 && selectionStart < length)
{
/*
* Cursor position anywhere in between
* Backspace and Delete have the same effect
*/
if (key == Keys.Back || key == Keys.Delete)
{
adminPassword = new string(adminPassword).Remove(selectionStart, 1).ToCharArray();
}
}
else if (selectionStart == length)
{
/*
* Cursor at the end, after the last character
* Delete the character only when Back key is pressed, No action when Delete key is pressed
*/
if (key == Keys.Back)
{
adminPassword = new string(adminPassword).Remove(selectionStart - 1, 1).ToCharArray();
}
}
}
this.Select((selectionStart > this.Text.Length ? this.Text.Length : selectionStart), 0);
}
private void ClearCharBufferPlusTextBox()
{
Array.Clear(adminPassword, 0, adminPassword.Length);
this.Clear();
}
}
}
编译代码并将其添加到 C# Winform 中进行测试，并报告您发现的任何问题。在提出您宝贵的意见时请友善。我们都在这里学习和改进。
已知问题
期待读者的反馈。
历史
v1.0：这是我工作的一个初始版本。没有特殊处理来过滤特殊字符。这将在未来进行处理。
v1.1：修复了一个错误，即第一个字符没有自动遮蔽。
v1.2：修复了一个错误，即密码字段接受超过 8 个字符。
v1.3：修复了一个错误，即密码字段接受超过 8 个字符。
v1.4：修复了一个错误，即当用户尝试编辑中间的密码字符时，光标位置会移动到末尾。