WPF中的自定义屏蔽密码框

Question

在iOS中,当您在字段中键入密码时,将显示该字段的最后一个字母,但在您键入下一个字符时会对其进行模糊处理.有没有办法在WPF中复制此行为？

Answer 1

好的,如果您在桌面应用程序中使用此类内容是合理的,那么您可以执行以下操作.

我们之前有类似的要求,这就是我所做的.

• 我Passwordbox通过从中派生TextBox并添加新的DP类型SecureString来创建自定义.(与正常情况几乎相同的概念PasswordBox).我们不会以这种方式放弃任何安全利益,并可以根据我们内心的内容定制视觉行为.
• 有了这个,现在我们可以使用Text的TextBox,因为它的显示字符串,并持有后端的实际密码SecureStringDP并将其绑定到虚拟机.
• 我们处理PreviewTextInput和PreviewKeyDown事件来管理控件中的所有文本更改,包括类似的东西Key.Back,Key.Delete以及烦人的Key.Space(不会通过PreviewTextInput

iOS感觉:

对于确切的iOS行为,请注意更多注意事项.

1. 仅在向"当前字符串的结尾"添加新字符时显示最后一个字符(FlowDirection独立)
2. 在现有字符串之间编辑字符对掩码没有影响.
3. 显示的最后一个字符取决于定时器(如果闲置,则在一段时间后变为"*")
4. 控件中禁用了所有复制粘贴操作.

检测到文本更改时,前2个点可以很容易地处理,对于最后一个,我们可以使用a DispatcherTimer来相应地处理display-string.

所以把这一切放在一起我们最终得到:

/// <summary>
///   This class contains properties for CustomPasswordBox
/// </summary>
internal class CustomPasswordBox : TextBox {
  #region Member Variables
  /// <summary>
  ///   Dependency property to hold watermark for CustomPasswordBox
  /// </summary>
  public static readonly DependencyProperty PasswordProperty =
    DependencyProperty.Register(
      "Password", typeof(SecureString), typeof(CustomPasswordBox), new UIPropertyMetadata(new SecureString()));

  /// <summary>
  ///   Private member holding mask visibile timer
  /// </summary>
  private readonly DispatcherTimer _maskTimer;
  #endregion

  #region Constructors
  /// <summary>
  ///   Initialises a new instance of the LifeStuffPasswordBox class.
  /// </summary>
  public CustomPasswordBox() {
    PreviewTextInput += OnPreviewTextInput;
    PreviewKeyDown += OnPreviewKeyDown;
    CommandManager.AddPreviewExecutedHandler(this, PreviewExecutedHandler);
    _maskTimer = new DispatcherTimer { Interval = new TimeSpan(0, 0, 0, 1) };
    _maskTimer.Tick += (sender, args) => MaskAllDisplayText();
  }
  #endregion

  #region Commands & Properties
  /// <summary>
  ///   Gets or sets dependency Property implementation for Password
  /// </summary>
  public SecureString Password {
    get {
      return (SecureString)GetValue(PasswordProperty);
    }

    set {
      SetValue(PasswordProperty, value);
    }
  }
  #endregion

  #region Methods
  /// <summary>
  ///   Method to handle PreviewExecutedHandler events
  /// </summary>
  /// <param name="sender">Sender object</param>
  /// <param name="executedRoutedEventArgs">Event Text Arguments</param>
  private static void PreviewExecutedHandler(object sender, ExecutedRoutedEventArgs executedRoutedEventArgs) {
    if (executedRoutedEventArgs.Command == ApplicationCommands.Copy ||
        executedRoutedEventArgs.Command == ApplicationCommands.Cut ||
        executedRoutedEventArgs.Command == ApplicationCommands.Paste) {
      executedRoutedEventArgs.Handled = true;
    }
  }

  /// <summary>
  ///   Method to handle PreviewTextInput events
  /// </summary>
  /// <param name="sender">Sender object</param>
  /// <param name="textCompositionEventArgs">Event Text Arguments</param>
  private void OnPreviewTextInput(object sender, TextCompositionEventArgs textCompositionEventArgs) {
    AddToSecureString(textCompositionEventArgs.Text);
    textCompositionEventArgs.Handled = true;
  }

  /// <summary>
  ///   Method to handle PreviewKeyDown events
  /// </summary>
  /// <param name="sender">Sender object</param>
  /// <param name="keyEventArgs">Event Text Arguments</param>
  private void OnPreviewKeyDown(object sender, KeyEventArgs keyEventArgs) {
    Key pressedKey = keyEventArgs.Key == Key.System ? keyEventArgs.SystemKey : keyEventArgs.Key;
    switch (pressedKey) {
      case Key.Space:
        AddToSecureString(" ");
        keyEventArgs.Handled = true;
        break;
      case Key.Back:
      case Key.Delete:
        if (SelectionLength > 0) {
          RemoveFromSecureString(SelectionStart, SelectionLength);
        } else if (pressedKey == Key.Delete && CaretIndex < Text.Length) {
          RemoveFromSecureString(CaretIndex, 1);
        } else if (pressedKey == Key.Back && CaretIndex > 0) {
          int caretIndex = CaretIndex;
          if (CaretIndex > 0 && CaretIndex < Text.Length)
            caretIndex = caretIndex - 1;
          RemoveFromSecureString(CaretIndex - 1, 1);
          CaretIndex = caretIndex;
        }

        keyEventArgs.Handled = true;
        break;
    }
  }

  /// <summary>
  ///   Method to add new text into SecureString and process visual output
  /// </summary>
  /// <param name="text">Text to be added</param>
  private void AddToSecureString(string text) {
    if (SelectionLength > 0) {
      RemoveFromSecureString(SelectionStart, SelectionLength);
    }

    foreach (char c in text) {
      int caretIndex = CaretIndex;
      Password.InsertAt(caretIndex, c);
      MaskAllDisplayText();
      if (caretIndex == Text.Length) {
        _maskTimer.Stop();
        _maskTimer.Start();
        Text = Text.Insert(caretIndex++, c.ToString());
      } else {
        Text = Text.Insert(caretIndex++, "*");
      }
      CaretIndex = caretIndex;
    }
  }

  /// <summary>
  ///   Method to remove text from SecureString and process visual output
  /// </summary>
  /// <param name="startIndex">Start Position for Remove</param>
  /// <param name="trimLength">Length of Text to be removed</param>
  private void RemoveFromSecureString(int startIndex, int trimLength) {
    int caretIndex = CaretIndex;
    for (int i = 0; i < trimLength; ++i) {
      Password.RemoveAt(startIndex);
    }

    Text = Text.Remove(startIndex, trimLength);
    CaretIndex = caretIndex;
  }

  private void MaskAllDisplayText() {
    _maskTimer.Stop();
    int caretIndex = CaretIndex;
    Text = new string('*', Text.Length);
    CaretIndex = caretIndex;
  }
  #endregion
}

工作样本:

下载链接

您可以在控件中键入内容并检查下面显示的存储值.

在这个示例中,我添加了一个新的DP类型,string以显示控件正常工作.您不希望HiddenText在您的实时代码中使用该DP(),但我希望该示例有助于分析该类是否真正有效:)