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
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。
只使用XAML,没有扩展,没有转换器:
<Grid>
<TextBox Width="250" VerticalAlignment="Center" HorizontalAlignment="Left" x:Name="SearchTermTextBox" Margin="5"/>
<TextBlock IsHitTestVisible="False" Text="Enter Search Term Here" VerticalAlignment="Center" HorizontalAlignment="Left" Margin="10,0,0,0" Foreground="DarkGray">
<TextBlock.Style>
<Style TargetType="{x:Type TextBlock}">
<Setter Property="Visibility" Value="Collapsed"/>
<Style.Triggers>
<DataTrigger Binding="{Binding Text, ElementName=SearchTermTextBox}" Value="">
<Setter Property="Visibility" Value="Visible"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBlock.Style>
</TextBlock>
</Grid>
我发现这个方法非常快速和简单
<ComboBox x:Name="comboBox1" SelectedIndex="0" HorizontalAlignment="Left" Margin="202,43,0,0" VerticalAlignment="Top" Width="149">
<ComboBoxItem Visibility="Collapsed">
<TextBlock Foreground="Gray" FontStyle="Italic">Please select ...</TextBlock>
</ComboBoxItem>
<ComboBoxItem Name="cbiFirst1">First Item</ComboBoxItem>
<ComboBoxItem Name="cbiSecond1">Second Item</ComboBoxItem>
<ComboBoxItem Name="cbiThird1">third Item</ComboBoxItem>
</ComboBox>
也许它能帮助到任何想这么做的人
来源:http://www.admindiaries.com/displaying-a-please-select-watermark-type-text-in-a-wpf-combobox/
最简单的方法水印的文本框
<Window.Resources>
<Style x:Key="MyWaterMarkStyle" TargetType="{x:Type TextBox}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type TextBox}">
<Grid>
<Border Background="White" BorderBrush="#FF7D8683" BorderThickness="1"/>
<ScrollViewer x:Name="PART_ContentHost" Margin="5,0,0,0" VerticalAlignment="Center" />
<Label Margin="5,0,0,0" x:Name="WaterMarkLabel" Content="{TemplateBinding Tag}" VerticalAlignment="Center"
Visibility="Collapsed" Foreground="Gray" FontFamily="Arial"/>
</Grid>
<ControlTemplate.Triggers>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="Text" Value=""/>
</MultiTrigger.Conditions>
<Setter Property="Visibility" TargetName="WaterMarkLabel" Value="Visible"/>
</MultiTrigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Foreground" Value="DimGray"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Window.Resources>
并添加文本框StaticResource样式
<TextBox
Style="{StaticResource MyWaterMarkStyle}"
Tag="Search Category"
Grid.Row="0"
Text="{Binding CategorySearch,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
TextSearch.Text="Search Category"
>
<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。
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