在iOS中,当您在字段中输入密码时,字段的最后一个字母会显示,但在您输入下一个字符时会被模糊处理。有没有办法在WPF中复制这种行为?
在iOS中,当您在字段中输入密码时,字段的最后一个字母会显示,但在您输入下一个字符时会被模糊处理。有没有办法在WPF中复制这种行为?
如果您需要在桌面应用中使用此类功能,可以采取以下方法:
我们之前也有过类似的需求,我采取了如下措施:
TextBox
派生并添加一个新的类型为SecureString
的DP(与普通的PasswordBox
相同)来创建一个自定义的Passwordbox
。这样做不会失去任何安全性,并且可以自定义视觉行为。TextBox
的Text
用作其显示字符串,并将实际密码保存在后端的SecureString
DP中并将其绑定到VM。PreviewTextInput
和PreviewKeyDown
事件来管理控件中的所有文本更改,包括一些非常烦人的键盘按键(如Key.Back
, Key.Delete
和不经过PreviewTextInput
的Key.Space
)iOS感受:
还有几件事情需要注意以获得精确的iOS行为:
FlowDirection
无关)当检测到文本更改时,前两点很容易处理,对于最后一点,我们可以使用DispatcherTimer
相应地处理显示字符串。
因此,将所有这些组合在一起,我们得到:
/// <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
}
示例:
您可以在控件中输入一些内容,并检查下方显示的存储值。
在此示例中,我添加了一个新的类型为string
的DP,仅用于展示该控件的正常运行。在实际代码中,您显然不希望拥有该 DP(HiddenText
),但我希望该示例能够帮助分析这个类是否真正起作用 :)