UWP 自定义密码框控件

1. 概述

微软官方有提供自己的密码控件，但是控件默认的行为是输入密码，会立即显示掩码，比如 *。如果像查看真实的文本，需要按查看按钮。

而我现在自定义的密码控件是先显示你输入的字符2s，然后再显示成掩码。当然这种场景并不一定适用于密码，也可以用在Pin码。

a. 微软官方的密码框

 

b. 自定义的效果

2. 密码框控件实现

要想实现自定义的密码框，我们当然要继承微软的TextBox控件，然后加入我们自己需要的东西。

a. 这里添加了一个加密类型的密码 Password 字段，真实密码文本 RealPassword 字段，一个Timer定时器来控制显示掩码

internal class CustomPasswordBox : TextBox
    {
        #region Member Variables
        public static readonly DependencyProperty PasswordProperty =
            DependencyProperty.Register("Password", typeof(SecureString), typeof(CustomPasswordBox), new PropertyMetadata(new SecureString()));

        public static readonly DependencyProperty RealPasswordProperty =
            DependencyProperty.Register("RealPassword", typeof(string), typeof(CustomPasswordBox), new PropertyMetadata(string.Empty));

        private DispatcherTimer maskTimer;
        #endregion
    }

b. 公开控件属性字段

public SecureString Password
        {
            get
            {
                return (SecureString)GetValue(PasswordProperty);
            }

            set
            {
                SetValue(PasswordProperty, value);
            }
        }


        public string RealPassword
        {
            get
            {
                return (string)GetValue(RealPasswordProperty);
            }

            set
            {
                SetValue(RealPasswordProperty, value);
            }
        }

c. 然后再构造函数里添加一个需要相应的事件，还有初始化Timer

public CustomPasswordBox()
        {
            PreviewKeyDown += CustomPasswordBox_PreviewKeyDown;
            CharacterReceived += CustomPasswordBox_CharacterReceived;
            BeforeTextChanging += CustomPasswordBox_BeforeTextChanging;
            SelectionChanged += CustomPasswordBox_SelectionChanged;
            ContextMenuOpening += CustomPasswordBox_ContextMenuOpening;
            TextCompositionStarted += CustomPasswordBox_TextCompositionStarted;

            maskTimer = new DispatcherTimer { Interval = new TimeSpan(0, 0, 2) };
            maskTimer.Tick += MaskTimer_Tick;
        }

在PreviewKeyDown、CharacterReceived、BeforeTextChanging这三个事件里，主要处理字符的输入删除等逻辑。
在SelectionChanged事件里，我们主要处理不让用户选中文本
在ContextMenuOpening，主要是屏蔽右键菜单，比如复制剪切粘贴
在TextCompositionStarted主要屏蔽中文等组合输入法

另外，在我的场景里面，我们只让用户输入数字，所以加入了数字验证，以及在Xbox上开启了InputScope=NumbericPin模式。

d. 添加事件响应代码

private void CustomPasswordBox_PreviewKeyDown(object sender, Windows.UI.Xaml.Input.KeyRoutedEventArgs e)
        {
            switch (e.OriginalKey)
            {
                case VirtualKey.Back:
                case VirtualKey.Delete:
                    if (SelectionLength > 0)
                    {
                        RemoveFromSecureString(SelectionStart, SelectionLength);
                    }
                    else if (e.OriginalKey == VirtualKey.Delete && SelectionStart < Text.Length)
                    {
                        RemoveFromSecureString(SelectionStart, 1);
                    }
                    else if (e.OriginalKey == VirtualKey.Back && SelectionStart > 0)
                    {
                        int caretIndex = SelectionStart;
                        if (SelectionStart > 0 && SelectionStart < Text.Length)
                            caretIndex = caretIndex - 1;
                        RemoveFromSecureString(SelectionStart - 1, 1);
                        //SelectionStart = caretIndex;
                    }

                    e.Handled = true;
                    break;

                default:
                    //e.Handled = true;
                    break;
            }
        }

        private void CustomPasswordBox_CharacterReceived(UIElement sender, Windows.UI.Xaml.Input.CharacterReceivedRoutedEventArgs args)
        {
            if (!char.IsDigit(args.Character))
                return;

            AddToSecureString(args.Character.ToString());
            args.Handled = true;
        }

        private void CustomPasswordBox_BeforeTextChanging(TextBox sender, TextBoxBeforeTextChangingEventArgs args)
        {
            args.Cancel = args.NewText.Any(c => !char.IsDigit(c) && !char.ToString(c).ToString().Equals("●"));
            //if (args.NewText.Replace("●", "") != "")
            //    AddToSecureString(args.NewText.Replace("●", ""));
        }

        private void CustomPasswordBox_ContextMenuOpening(object sender, ContextMenuEventArgs e)
        {
            e.Handled = true;
        }

        private void CustomPasswordBox_SelectionChanged(object sender, RoutedEventArgs e)
        {
            SelectionStart = Text.Length;
            SelectionLength = 0;
        }

        private void CustomPasswordBox_TextCompositionStarted(TextBox sender, TextCompositionStartedEventArgs args)
        {
            return;
        }

        private void MaskTimer_Tick(object sender, object e)
        {
            MaskAllDisplayText();
        }

e. 实现Timer里面的2s后将字符串变成掩码

2s后看TextBox里面的字符数，然后设置对应长度的掩码

        private void MaskAllDisplayText()
        {
            maskTimer.Stop();
            int caretIndex = SelectionStart;
            Text = new string('●', Text.Length);
            SelectionStart = caretIndex;
        }

f. 添加字符和删除字符

 private void AddToSecureString(string text)
        {
            if (SelectionLength > 0)
            {
                RemoveFromSecureString(SelectionStart, SelectionLength);
            }

            if (Password.Length >= 4 || RealPassword.Length >= 4)
                return;
            foreach (char c in text)
            {
                System.Diagnostics.Debug.WriteLine(text);
                int caretIndex = SelectionStart;
                if (caretIndex - 1 < 0)
                    Password.InsertAt(0, c);
                else
                    Password.InsertAt(caretIndex - 1, c);
                RealPassword += c.ToString();
                //MaskAllDisplayText();
                if (caretIndex == Text.Length)
                {
                    maskTimer.Stop();
                    maskTimer.Start();
                    //Text = Text.Insert(caretIndex++, c.ToString());
                }
                else
                {
                    //Text = Text.Insert(caretIndex++, "●");
                }
                SelectionStart = Text.Length;
            }
        }

        private void RemoveFromSecureString(int startIndex, int trimLength)
        {
            int caretIndex = SelectionStart;
            for (int i = 0; i < trimLength; ++i)
            {
                Password.RemoveAt(startIndex);
                RealPassword = RealPassword.Remove(startIndex, 1);
            }

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

3. 控件使用方法

<local:CustomPasswordBox
            InputScope="NumericPin"
            MaxLength="4" />

一个例子

<Grid>
        <local:CustomPasswordBox
            x:Name="PSW"
            InputScope="NumericPin"
            Padding="200 0 0 0"
            Style="{StaticResource MyTextBox}"
            Height="Auto"
            MaxLength="4"
            CharacterSpacing="1000"
            FontSize="100"
            VerticalAlignment="Top"/>
        <TextBlock
            x:Name="realPSW"
            FontSize="88"
            Margin="0 200"
            HorizontalAlignment="Center"
            Text="{Binding ElementName=PSW, Path=RealPassword, Mode=OneWay}"/>
    </Grid>

你也可以看我在Youtube上的视频演示

https://youtu.be/eHhDG3dW1bI

欢迎点击右下角的订阅按钮，还有红色小铃铛。谢谢