WindowsPhone自定义控件详解（三） - 实战：自定义带水印的PasswordBox控件，WatermarkedPasswordBox

一时失言乱红尘 2022-06-15 01:09 267阅读 0赞

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本文系本站原创,欢迎转载! 转载请注明出处:

[http://blog.csdn.net/mr\_raptor/article/details/7251992][http_blog.csdn.net_mr_raptor_article_details_7251992]

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声明：这个控件是在WatermarkedTextBox的基础上改的。

*  从[http://www.windowsphonegeek.com/articles/WP7-WatermarkedTextBox-custom-control][http_www.windowsphonegeek.com_articles_WP7-WatermarkedTextBox-custom-control]上下载WatermarkedTextBox控件

[原创地址：][http_blog.csdn.net_mr_raptor_article_details_7251992][http://blog.csdn.net/mr\_raptor/article/details/7251992][http_blog.csdn.net_mr_raptor_article_details_7251992]

**原理分析：**

在PasswordBox后面加水印和在TextBox后面加水印差不多，有以下要求：

1.  PasswordBox里没内容时，显示水印
2.  PasswordBox里有内容时，不显示水印，而显示内容

最简单的想法就是，在PasswordBox控件后面加上一个类似TextBlock的控件，然后重写焦点回调方法，当有焦点时，水印不显示，无焦点时，根据是否有内容而决定是否显示水印。

思路如上，下面开始分析WatermarkedTextBox的代码，看看它的作者是不是和我们想法一样。

**一、 分析WatermarkedTextBox代码**

1.  themes/generic.xaml

自定义控件的样式文件必须要以generic.xaml命名，放到themes目录中。

*注：上面省略了一部分无关紧要代码。*  
[http://blog.csdn.net/mr\_raptor/article/details/7251992][http_blog.csdn.net_mr_raptor_article_details_7251992]

上面的XAML文件，定义了WatermarkedTextBox的样式：

*  文件开始，定义了一个ControlTemplate元素，由前两节知识可知，它是要对一个控件设置模板，从后面的TargetType="TextBox"可知，是针对TextBox类型控件，它里面自定义了一个ContentControl类名字为ContentElement。
 *  通过TargetType="local:WatermarkedTextBox" 可知，它是针对WatermarkedTextBox的控件样式。
 *  在EnabledBorder里定义了两个内容控件元素：watermarkContent和ContentElement，watermarkContent里，绑定了依赖属性Watermark（在WatermarkTextBox.cs里声明）。
 *  在下面的DisabledOrReadonlyBorder里面是一个TextBox 控件，它绑定了WatermarkedTextBox里的Text属性，同时这个TextBox 控件，的模板设置为：PhoneDisabledTextBoxTemplate，它这么做的目的是，可以设置WatermarkedTextBox的属性为Disabled，这时，水印就消失了，而显示原先的TextBox控件。

2. WatermarkTextBox.cs

namespace WatermarkedTextBoxControl \{ public class WatermarkedTextBox : TextBox \{ ContentControl WatermarkContent; public static readonly DependencyProperty WatermarkProperty = DependencyProperty.Register("Watermark", typeof(object), typeof(WatermarkedTextBox), new PropertyMetadata(OnWatermarkPropertyChanged)); public static readonly DependencyProperty WatermarkStyleProperty = DependencyProperty.Register("WatermarkStyle", typeof(Style), typeof(WatermarkedTextBox), null); public Style WatermarkStyle \{ get \{ return base.GetValue(WatermarkStyleProperty) as Style; \} set \{ base.SetValue(WatermarkStyleProperty, value); \} \} public object Watermark \{ get \{ return base.GetValue(WatermarkProperty) as object; \} set \{ base.SetValue(WatermarkProperty, value); \} \} public WatermarkedTextBox() \{ DefaultStyleKey = typeof(WatermarkedTextBox); \} public override void OnApplyTemplate() \{ base.OnApplyTemplate(); this.WatermarkContent = this.GetTemplateChild("watermarkContent") as ContentControl; if(WatermarkContent != null) \{ DetermineWatermarkContentVisibility(); \} \} protected override void OnGotFocus(RoutedEventArgs e) \{ if (WatermarkContent != null && string.IsNullOrEmpty(this.Text)) \{ this.WatermarkContent.Visibility = Visibility.Collapsed; \} base.OnGotFocus(e); \} protected override void OnLostFocus(RoutedEventArgs e) \{ if (WatermarkContent != null && string.IsNullOrEmpty(this.Text)) \{ this.WatermarkContent.Visibility = Visibility.Visible; \} base.OnLostFocus(e); \} private static void OnWatermarkPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args) \{ WatermarkedTextBox watermarkTextBox = sender as WatermarkedTextBox; if(watermarkTextBox != null && watermarkTextBox.WatermarkContent !=null) \{ watermarkTextBox.DetermineWatermarkContentVisibility(); \} \} private void DetermineWatermarkContentVisibility() \{ if (string.IsNullOrEmpty(this.Text)) \{ this.WatermarkContent.Visibility = Visibility.Visible; \} else \{ this.WatermarkContent.Visibility = Visibility.Collapsed; \} \} \} \} \}

[原创地址：][http_blog.csdn.net_mr_raptor_article_details_7251992][http://blog.csdn.net/mr\_raptor/article/details/7251992][http_blog.csdn.net_mr_raptor_article_details_7251992]  
由这个WatermarkedTextBox类可知：

*  它继承了TextBox类
 *  增加了Watermark和WatermarkStyle两个依赖属性，用于用户设置它的水印内容和样式，在Watermark属性里添加了属性改变事件：OnWatermarkPropertyChanged
 *  重载了OnApplyTemplate方法来取得generic.xaml文件里声明的元素引用：watermarkContent，并且根据generic.xaml里的TextBox ：DisabledOrReadonlyContent，取得它里面是否有内容，如果有内容，则WatermarkContent不可见，否则WatermarkContent可见。
 *  重载了OnGotFocus，OnLostFocus，当该自定义控件得到焦点时，设置WatermarkContent不可见，否则WatermarkContent可见。

由上面的分析可知，当用户设置了自定义控件的Watermark属性时，回调注册的OnWatermarkPropertyChanged方法，在该方法里，判断是否WatermarkContent里有内容，如果有，WatermarkContent不可见，否则WatermarkContent可见。两样，重载了OnGotFocus，OnLostFocus，在得到和失去焦点时也要判断是否将WatermarkContent设置为可见与否。

**二、 自定义WatermarkedPasswordBox**

根据前面的分析，我们可以试着做以下修改：

*  新建类WatermarkedPasswordBox
 *  将WatermarkTextBox.cs拷贝到类WatermarkedPasswordBox里，改下类名，让WatermarkedPasswordBox继承了Password类
 *  在themes/generic.xaml里，拷贝 <Style  TargetType="local:WatermarkedPasswordBox">里的全部代码，改为WatermarkedPasswordBox的代码，中间细节自己改就行了，我们不打算支持Disabled属性，所以DisabledOrReadonlyBorder去掉就行了，将EnabledBorder里的ContentElement去掉，换成PasswordBox，名字还是ContentElement

编译时，错误出现了：WatermarkedPasswordBox里this.Text出错，这是因为Password没有Text属性，它有个Password属性，所以要做下面的修改：

*  让WatermarkedPasswordBox类继承TextBox，但是添加一个属性：PasswordBox类型的PasswordContent
 *  在OnApplyTemplate方法里，获得自己加的PasswordBox控件的引用ContentElement，为PasswordBox控件添加PasswordChanged事件，当密码框里内容改变时，将TextBox的Text属性的值为PasswordBox.Password的值
 *  同样，在XAML样式文件里，在PasswordBox控件里加上 Password="\{TemplateBinding Text\}"

修改后的代码如下：

XAML：

原创地址：[http://blog.csdn.net/mr\_raptor/article/details/7251992][http_blog.csdn.net_mr_raptor_article_details_7251992]  
C\#：

public class WatermarkedPasswordBox : TextBox \{ ContentControl WatermarkContent; private PasswordBox PasswordContent; public object Watermark \{ get \{ return base.GetValue(WatermarkProperty) as object; \} set \{ base.SetValue(WatermarkProperty, value); \} \} public static readonly DependencyProperty WatermarkProperty = DependencyProperty.Register("Watermark", typeof(object), typeof(WatermarkedPasswordBox), new PropertyMetadata(OnWatermarkPropertyChanged)); private static void OnWatermarkPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs args) \{ WatermarkedPasswordBox watermarkTextBox = sender as WatermarkedPasswordBox; if (watermarkTextBox != null && watermarkTextBox.WatermarkContent != null) \{ watermarkTextBox.DetermineWatermarkContentVisibility(); \} Debug.WriteLine("OnWatermarkPropertyChanged"); \} public Style WatermarkStyle \{ get \{ return base.GetValue(WatermarkStyleProperty) as Style; \} set \{ base.SetValue(WatermarkStyleProperty, value); \} \} public static readonly DependencyProperty WatermarkStyleProperty = DependencyProperty.Register("WatermarkStyle", typeof(Style), typeof(WatermarkedPasswordBox), null); public WatermarkedPasswordBox() \{ DefaultStyleKey = typeof(WatermarkedPasswordBox); \} public override void OnApplyTemplate() \{ base.OnApplyTemplate(); this.WatermarkContent = this.GetTemplateChild("watermarkContent") as ContentControl; this.PasswordContent = this.GetTemplateChild("ContentElement") as PasswordBox; if (WatermarkContent != null && WatermarkContent != null) \{ PasswordContent.PasswordChanged += new RoutedEventHandler(PasswordContent\_PasswordChanged); DetermineWatermarkContentVisibility(); \} \} void PasswordContent\_PasswordChanged(object sender, RoutedEventArgs e) \{ PasswordBox passwdBx = sender as PasswordBox; this.Text = passwdBx.Password; \} protected override void OnGotFocus(RoutedEventArgs e) \{ if (WatermarkContent != null && WatermarkContent != null && string.IsNullOrEmpty(this.PasswordContent.Password)) \{ this.WatermarkContent.Visibility = Visibility.Collapsed; \} base.OnGotFocus(e); \} protected override void OnLostFocus(RoutedEventArgs e) \{ if (WatermarkContent != null && WatermarkContent != null && string.IsNullOrEmpty(this.PasswordContent.Password)) \{ this.WatermarkContent.Visibility = Visibility.Visible; \} base.OnLostFocus(e); \} private void DetermineWatermarkContentVisibility() \{ if (string.IsNullOrEmpty(this.PasswordContent.Password)) \{ this.WatermarkContent.Visibility = Visibility.Visible; \} else \{ this.WatermarkContent.Visibility = Visibility.Collapsed; \} \} \}

编译通过，将生成的库引入到Demo程序里，然后将控件加上，成功，效果如下。

左图，未输入内容，显示水印，右图，输入内容时显示效果。

![0_13289865977U4O.gif][]![0_1328986609Sxss.gif][]

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本文系本站原创,欢迎转载! 转载请注明出处:

[http://blog.csdn.net/mr\_raptor/article/details/7251992][http_blog.csdn.net_mr_raptor_article_details_7251992]

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[http_blog.csdn.net_mr_raptor_article_details_7251992]: http://blog.csdn.net/mr_raptor/article/details/7251992
[http_www.windowsphonegeek.com_articles_WP7-WatermarkedTextBox-custom-control]: http://www.windowsphonegeek.com/articles/WP7-WatermarkedTextBox-custom-control
[0_13289865977U4O.gif]: http://hi.csdn.net/attachment/201202/11/0_13289865977U4O.gif
[0_1328986609Sxss.gif]: /images/20220615/11b74b86e7654cea8db7c91522f2fc8c.png