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
如果水印的可见性不是取决于控件的焦点状态,而是取决于用户是否输入了任何文本,您可以将John Myczek的答案(从OnWatermarkChanged向下)更新为
static void OnWatermarkChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) {
var textbox = (TextBox)d;
textbox.Loaded += UpdateWatermark;
textbox.TextChanged += UpdateWatermark;
}
static void UpdateWatermark(object sender, RoutedEventArgs e) {
var textbox = (TextBox)sender;
var layer = AdornerLayer.GetAdornerLayer(textbox);
if (layer != null) {
if (textbox.Text == string.Empty) {
layer.Add(new WatermarkAdorner(textbox, GetWatermark(textbox)));
} else {
var adorners = layer.GetAdorners(textbox);
if (adorners == null) {
return;
}
foreach (var adorner in adorners) {
if (adorner is WatermarkAdorner) {
adorner.Visibility = Visibility.Hidden;
layer.Remove(adorner);
}
}
}
}
}
如果文本框在显示表单或绑定到Text属性时自动获得焦点,这就更有意义了。
同样,如果你的水印总是一个字符串,你需要水印的风格来匹配文本框的风格,那么在Adorner做:
contentPresenter = new ContentPresenter {
Content = new TextBlock {
Text = (string)watermark,
Foreground = Control.Foreground,
Background = Control.Background,
FontFamily = Control.FontFamily,
FontSize = Control.FontSize,
...
},
...
}
其他回答
这里有一个最简单的解决方案:
<Grid>
<Label Content="Placeholder text" VerticalAlignment="Center" Margin="10">
<Label.Style>
<Style TargetType="Label">
<Setter Property="Foreground" Value="Transparent"/>
<Style.Triggers>
<DataTrigger Binding="{Binding Expression}" Value="">
<Setter Property="Foreground" Value="Gray"/>
</DataTrigger>
</Style.Triggers>
</Style>
</Label.Style>
</Label>
<TextBox HorizontalAlignment="Stretch" Margin="5" Background="Transparent"
Text="{Binding Expression, UpdateSourceTrigger=PropertyChanged}" VerticalAlignment="Center" Padding="5">
</TextBox>
</Grid>
这是一个透明背景覆盖标签的文本框。标签的灰色文本通过数据触发器变成透明的,只要绑定的文本不是空字符串就会触发该触发器。
<TextBox Controls:TextBoxHelper.Watermark="Watermark"/>
添加mahapps。地铁到你的项目。 将带有上述代码的文本框添加到窗口中。
@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);
}
}
}
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"
>
<TextBox x:Name="OrderTxt" HorizontalAlignment="Left" VerticalAlignment="Top" VerticalContentAlignment="Center" Margin="10,10,0,0" Width="188" Height="32"/>
<Label IsHitTestVisible="False" Content="Order number" DataContext="{Binding ElementName=OrderTxt}" Foreground="DarkGray">
<Label.Style>
<Style TargetType="{x:Type Label}">
<Setter Property="Visibility" Value="Collapsed"/>
<Setter Property="Width" Value="{Binding Width}"/>
<Setter Property="Height" Value="{Binding Height}"/>
<Setter Property="Margin" Value="{Binding Margin}"/>
<Setter Property="VerticalAlignment" Value="{Binding VerticalAlignment}"/>
<Setter Property="HorizontalAlignment" Value="{Binding HorizontalAlignment}"/>
<Setter Property="VerticalContentAlignment" Value="{Binding VerticalContentAlignment}"/>
<Style.Triggers>
<DataTrigger Binding="{Binding Text}" Value="">
<Setter Property="Visibility" Value="Visible"/>
</DataTrigger>
</Style.Triggers>
</Style>
</Label.Style>
</Label>
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