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
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;
}
}
其他回答
设置文本框的占位符文本在一个柔和的颜色…
public MainWindow ( )
{
InitializeComponent ( );
txtInput.Text = "Type something here...";
txtInput.Foreground = Brushes.DimGray;
}
当文本框获得焦点时，清除它并更改文本颜色
private void txtInput_GotFocus ( object sender, EventArgs e )
{
MessageBox.Show ( "got focus" );
txtInput.Text = "";
txtInput.Foreground = Brushes.Red;
}
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;
}
}
你可以使用GetFocus()和LostFocus()事件来做到这一点
下面是例子:
private void txtData1_GetFocus(object sender, RoutedEventArgs e)
{
if (txtData1.Text == "TextBox1abc")
{
txtData1.Text = string.Empty;
}
}
private void txtData1_LostFocus(object sender, RoutedEventArgs e)
{
if (txtData1.Text == string.Empty)
{
txtData1.Text = "TextBox1abc";
}
}
这是一个演示如何在WPF中创建水印文本框的示例:
<Window x:Class="WaterMarkTextBoxDemo.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="clr-namespace:WaterMarkTextBoxDemo"
Height="200" Width="400">
<Window.Resources>
<SolidColorBrush x:Key="brushWatermarkBackground" Color="White" />
<SolidColorBrush x:Key="brushWatermarkForeground" Color="LightSteelBlue" />
<SolidColorBrush x:Key="brushWatermarkBorder" Color="Indigo" />
<BooleanToVisibilityConverter x:Key="BooleanToVisibilityConverter" />
<local:TextInputToVisibilityConverter x:Key="TextInputToVisibilityConverter" />
<Style x:Key="EntryFieldStyle" TargetType="Grid" >
<Setter Property="HorizontalAlignment" Value="Stretch" />
<Setter Property="VerticalAlignment" Value="Center" />
<Setter Property="Margin" Value="20,0" />
</Style>
</Window.Resources>
<Grid Background="LightBlue">
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<Grid Grid.Row="0" Background="{StaticResource brushWatermarkBackground}" Style="{StaticResource EntryFieldStyle}" >
<TextBlock Margin="5,2" Text="This prompt dissappears as you type..." Foreground="{StaticResource brushWatermarkForeground}"
Visibility="{Binding ElementName=txtUserEntry, Path=Text.IsEmpty, Converter={StaticResource BooleanToVisibilityConverter}}" />
<TextBox Name="txtUserEntry" Background="Transparent" BorderBrush="{StaticResource brushWatermarkBorder}" />
</Grid>
<Grid Grid.Row="1" Background="{StaticResource brushWatermarkBackground}" Style="{StaticResource EntryFieldStyle}" >
<TextBlock Margin="5,2" Text="This dissappears as the control gets focus..." Foreground="{StaticResource brushWatermarkForeground}" >
<TextBlock.Visibility>
<MultiBinding Converter="{StaticResource TextInputToVisibilityConverter}">
<Binding ElementName="txtUserEntry2" Path="Text.IsEmpty" />
<Binding ElementName="txtUserEntry2" Path="IsFocused" />
</MultiBinding>
</TextBlock.Visibility>
</TextBlock>
<TextBox Name="txtUserEntry2" Background="Transparent" BorderBrush="{StaticResource brushWatermarkBorder}" />
</Grid>
</Grid>
</Window>
TextInputToVisibilityConverter定义为:
using System;
using System.Windows.Data;
using System.Windows;
namespace WaterMarkTextBoxDemo
{
public class TextInputToVisibilityConverter : IMultiValueConverter
{
public object Convert( object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture )
{
// Always test MultiValueConverter inputs for non-null
// (to avoid crash bugs for views in the designer)
if (values[0] is bool && values[1] is bool)
{
bool hasText = !(bool)values[0];
bool hasFocus = (bool)values[1];
if (hasFocus || hasText)
return Visibility.Collapsed;
}
return Visibility.Visible;
}
public object[] ConvertBack( object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture )
{
throw new NotImplementedException();
}
}
}
注意:这不是我的代码。我是在这里找到的，但我认为这是最好的方法。
嗨，我把这个任务变成了一个行为。你只需要在文本框中添加这样的东西
<i:Interaction.Behaviors>
<Behaviors:TextBoxWatermarkBehavior Label="Test Watermark" LabelStyle="{StaticResource StyleWatermarkLabel}"/>
</i:Interaction.Behaviors>
你可以在这里找到我的博客文章
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