我怎么能把一些文本放入一个文本框，这将被自动删除时，用户键入的东西在它?
当前回答
@Veton -我真的很喜欢你的解决方案的简单性，但我的声誉还没有高到足以撞到你。
@Tim Murphy -“双向绑定需要Path或XPath”的错误很容易修复…更新的代码，包括一些其他的小调整(仅WPF测试):
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Media;
public class TextBoxWatermarked : TextBox
{
public string Watermark
{
get { return (string)GetValue(WaterMarkProperty); }
set { SetValue(WaterMarkProperty, value); }
}
public static readonly DependencyProperty WaterMarkProperty =
DependencyProperty.Register("Watermark", typeof(string), typeof(TextBoxWatermarked), new PropertyMetadata(new PropertyChangedCallback(OnWatermarkChanged)));
private bool _isWatermarked = false;
private Binding _textBinding = null;
public TextBoxWatermarked()
{
Loaded += (s, ea) => ShowWatermark();
}
protected override void OnGotFocus(RoutedEventArgs e)
{
base.OnGotFocus(e);
HideWatermark();
}
protected override void OnLostFocus(RoutedEventArgs e)
{
base.OnLostFocus(e);
ShowWatermark();
}
private static void OnWatermarkChanged(DependencyObject sender, DependencyPropertyChangedEventArgs ea)
{
var tbw = sender as TextBoxWatermarked;
if (tbw == null || !tbw.IsLoaded) return; //needed to check IsLoaded so that we didn't dive into the ShowWatermark() routine before initial Bindings had been made
tbw.ShowWatermark();
}
private void ShowWatermark()
{
if (String.IsNullOrEmpty(Text) && !String.IsNullOrEmpty(Watermark))
{
_isWatermarked = true;
//save the existing binding so it can be restored
_textBinding = BindingOperations.GetBinding(this, TextProperty);
//blank out the existing binding so we can throw in our Watermark
BindingOperations.ClearBinding(this, TextProperty);
//set the signature watermark gray
Foreground = new SolidColorBrush(Colors.Gray);
//display our watermark text
Text = Watermark;
}
}
private void HideWatermark()
{
if (_isWatermarked)
{
_isWatermarked = false;
ClearValue(ForegroundProperty);
Text = "";
if (_textBinding != null) SetBinding(TextProperty, _textBinding);
}
}
}
其他回答
<Window.Resources>
<Style x:Key="TextBoxUserStyle" BasedOn="{x:Null}" TargetType="{x:Type TextBox}">
<Setter Property="Foreground" Value="Black"/>
<Setter Property="HorizontalAlignment" Value="Center"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Width" Value="225"/>
<Setter Property="Height" Value="25"/>
<Setter Property="FontSize" Value="12"/>
<Setter Property="Padding" Value="1"/>
<Setter Property="Margin" Value="5"/>
<Setter Property="AllowDrop" Value="true"/>
<Setter Property="FocusVisualStyle" Value="{x:Null}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TextBox}">
<Border x:Name="OuterBorder" BorderBrush="#5AFFFFFF" BorderThickness="1,1,1,1" CornerRadius="4,4,4,4">
<Border x:Name="InnerBorder" Background="#FFFFFFFF" BorderBrush="#33000000" BorderThickness="1,1,1,1" CornerRadius="3,3,3,3">
<ScrollViewer SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" x:Name="PART_ContentHost"/>
</Border>
</Border>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style x:Key="PasswordBoxVistaStyle" BasedOn="{x:Null}" TargetType="{x:Type PasswordBox}">
<Setter Property="Foreground" Value="Black"/>
<Setter Property="HorizontalAlignment" Value="Center"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Width" Value="225"/>
<Setter Property="Height" Value="25"/>
<Setter Property="FontSize" Value="12"/>
<Setter Property="Padding" Value="1"/>
<Setter Property="Margin" Value="5"/>
<Setter Property="AllowDrop" Value="true"/>
<Setter Property="FocusVisualStyle" Value="{x:Null}"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type PasswordBox}">
<Border x:Name="OuterBorder" BorderBrush="#5AFFFFFF" BorderThickness="1,1,1,1" CornerRadius="4,4,4,4">
<Border x:Name="InnerBorder" Background="#FFFFFFFF" BorderBrush="#33000000" BorderThickness="1,1,1,1" CornerRadius="3,3,3,3">
<Grid>
<Label x:Name="lblPwd" Content="Password" FontSize="11" VerticalAlignment="Center" Margin="2,0,0,0" FontFamily="Verdana" Foreground="#828385" Padding="0"/>
<ScrollViewer SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" x:Name="PART_ContentHost"/>
</Grid>
</Border>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsFocused" Value="True">
<Setter Property="Visibility" TargetName="lblPwd" Value="Hidden"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Window.Resources>
<PasswordBox Style="{StaticResource PasswordBoxVistaStyle}" Margin="169,143,22,0" Name="txtPassword" FontSize="14" TabIndex="2" Height="31" VerticalAlignment="Top" />
这可以帮助检查您的代码。当应用到密码框时，它将显示密码，当用户输入时，它将消失。
namespace PlaceholderForRichTexxBoxInWPF
{
public MainWindow()
{
InitializeComponent();
Application.Current.MainWindow.WindowState = WindowState.Maximized;// maximize window on load
richTextBox1.GotKeyboardFocus += new KeyboardFocusChangedEventHandler(rtb_GotKeyboardFocus);
richTextBox1.LostKeyboardFocus += new KeyboardFocusChangedEventHandler(rtb_LostKeyboardFocus);
richTextBox1.AppendText("Place Holder");
richTextBox1.Foreground = Brushes.Gray;
}
private void rtb_GotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
if (sender is RichTextBox)
{
TextRange textRange = new TextRange(richTextBox1.Document.ContentStart, richTextBox1.Document.ContentEnd);
if (textRange.Text.Trim().Equals("Place Holder"))
{
((RichTextBox)sender).Foreground = Brushes.Black;
richTextBox1.Document.Blocks.Clear();
}
}
}
private void rtb_LostKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
//Make sure sender is the correct Control.
if (sender is RichTextBox)
{
//If nothing was entered, reset default text.
TextRange textRange = new TextRange(richTextBox1.Document.ContentStart, richTextBox1.Document.ContentEnd);
if (textRange.Text.Trim().Equals(""))
{
((RichTextBox)sender).Foreground = Brushes.Gray;
((RichTextBox)sender).AppendText("Place Holder");
}
}
}
}
该技术使用Background属性来显示/隐藏占位符文本框。 占位符显示事件时，文本框有焦点
工作原理:
当为空时，文本框背景设置为透明以显示占位符文本。 当不空背景设置为白色，以掩盖占位符文本。
这里有一个基本的例子。出于我自己的目的，我把它变成了一个UserControl。
<Grid>
<Grid.Resources>
<ux:NotEmptyConverter x:Key="NotEmptyConverter" />
<Style TargetType="{x:Type Control}" x:Key="DefaultStyle">
<Setter Property="FontSize" Value="20" />
<Setter Property="Margin" Value="10"/>
<Setter Property="VerticalAlignment" Value="Center"></Setter>
<Setter Property="VerticalContentAlignment" Value="Center"></Setter>
</Style>
<Style TargetType="{x:Type TextBox}" BasedOn="{StaticResource DefaultStyle}"></Style>
</Grid.Resources>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
</Grid.RowDefinitions>
<TextBox Grid.Row="0" Text="Placeholder Text Is Here" Foreground="DarkGray" />
<TextBox Grid.Row="0" Name="TextBoxEdit"
Text="{Binding Path=FirstName, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" >
<TextBox.Style>
<Style TargetType="{x:Type TextBox}" BasedOn="{StaticResource DefaultStyle}">
<Style.Triggers>
<DataTrigger Binding="{Binding Path=FirstName.Length, FallbackValue=0, TargetNullValue=0}" Value="0">
<Setter Property="Background" Value="Transparent"/>
</DataTrigger>
<DataTrigger Binding="{Binding Path=FirstName, FallbackValue=0, TargetNullValue=0, Converter={StaticResource NotEmptyConverter}}" Value="false">
<Setter Property="Background" Value="White"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBox.Style>
</TextBox>
</Grid>
下面是ValueConverter，用于检测DataTrigger中的非空字符串。
public class NotEmptyConverter : IValueConverter
{
public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
var s = value as string;
return string.IsNullOrEmpty(s);
}
public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return null;
}
}
这个库有水印。
Nuget包
示例用法:
<TextBox adorners:Watermark.Text="Write something here"
adorners:Watermark.TextStyle="{StaticResource AdornerTextStyle}"
adorners:Watermark.VisibleWhen="EmptyAndNotKeyboardFocused"/>
@Veton -我真的很喜欢你的解决方案的简单性，但我的声誉还没有高到足以撞到你。
@Tim Murphy -“双向绑定需要Path或XPath”的错误很容易修复…更新的代码，包括一些其他的小调整(仅WPF测试):
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Media;
public class TextBoxWatermarked : TextBox
{
public string Watermark
{
get { return (string)GetValue(WaterMarkProperty); }
set { SetValue(WaterMarkProperty, value); }
}
public static readonly DependencyProperty WaterMarkProperty =
DependencyProperty.Register("Watermark", typeof(string), typeof(TextBoxWatermarked), new PropertyMetadata(new PropertyChangedCallback(OnWatermarkChanged)));
private bool _isWatermarked = false;
private Binding _textBinding = null;
public TextBoxWatermarked()
{
Loaded += (s, ea) => ShowWatermark();
}
protected override void OnGotFocus(RoutedEventArgs e)
{
base.OnGotFocus(e);
HideWatermark();
}
protected override void OnLostFocus(RoutedEventArgs e)
{
base.OnLostFocus(e);
ShowWatermark();
}
private static void OnWatermarkChanged(DependencyObject sender, DependencyPropertyChangedEventArgs ea)
{
var tbw = sender as TextBoxWatermarked;
if (tbw == null || !tbw.IsLoaded) return; //needed to check IsLoaded so that we didn't dive into the ShowWatermark() routine before initial Bindings had been made
tbw.ShowWatermark();
}
private void ShowWatermark()
{
if (String.IsNullOrEmpty(Text) && !String.IsNullOrEmpty(Watermark))
{
_isWatermarked = true;
//save the existing binding so it can be restored
_textBinding = BindingOperations.GetBinding(this, TextProperty);
//blank out the existing binding so we can throw in our Watermark
BindingOperations.ClearBinding(this, TextProperty);
//set the signature watermark gray
Foreground = new SolidColorBrush(Colors.Gray);
//display our watermark text
Text = Watermark;
}
}
private void HideWatermark()
{
if (_isWatermarked)
{
_isWatermarked = false;
ClearValue(ForegroundProperty);
Text = "";
if (_textBinding != null) SetBinding(TextProperty, _textBinding);
}
}
}
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