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
CodeProject上有一篇关于如何在“3行XAML”中做到这一点的文章。
<Grid Background="{StaticResource brushWatermarkBackground}">
<TextBlock Margin="5,2" Text="Type something..."
Foreground="{StaticResource brushForeground}"
Visibility="{Binding ElementName=txtUserEntry, Path=Text.IsEmpty,
Converter={StaticResource BooleanToVisibilityConverter}}" />
<TextBox Name="txtUserEntry" Background="Transparent"
BorderBrush="{StaticResource brushBorder}" />
</Grid>
好吧,它可能不是3行XAML格式的,但它非常简单。
需要注意的一点是:文本上的IsEmpty属性不是string的属性,而是ICollectionView的属性,并且可以显式地设置为Path=Text.(componentModel:ICollectionView.IsEmpty) (with xmlns:componentModel="clr-namespace:System.ComponentModel;assembly=WindowsBase")。这里有详细的解释。
其他回答
CodeProject上有一篇关于如何在“3行XAML”中做到这一点的文章。
<Grid Background="{StaticResource brushWatermarkBackground}">
<TextBlock Margin="5,2" Text="Type something..."
Foreground="{StaticResource brushForeground}"
Visibility="{Binding ElementName=txtUserEntry, Path=Text.IsEmpty,
Converter={StaticResource BooleanToVisibilityConverter}}" />
<TextBox Name="txtUserEntry" Background="Transparent"
BorderBrush="{StaticResource brushBorder}" />
</Grid>
好吧,它可能不是3行XAML格式的,但它非常简单。
需要注意的一点是:文本上的IsEmpty属性不是string的属性,而是ICollectionView的属性,并且可以显式地设置为Path=Text.(componentModel:ICollectionView.IsEmpty) (with xmlns:componentModel="clr-namespace:System.ComponentModel;assembly=WindowsBase")。这里有详细的解释。
我的解决办法很简单。
在我的登录窗口。xaml是这样的。
<DockPanel HorizontalAlignment="Center" VerticalAlignment="Center" Height="80" Width="300" LastChildFill="True">
<Button Margin="5,0,0,0" Click="login_Click" DockPanel.Dock="Right" VerticalAlignment="Center" ToolTip="Login to system">
Login
</Button>
<StackPanel>
<TextBox x:Name="userNameWatermarked" Height="25" Foreground="Gray" Text="UserName" GotFocus="userNameWatermarked_GotFocus"></TextBox>
<TextBox x:Name="userName" Height="25" TextChanged="loginElement_TextChanged" Visibility="Collapsed" LostFocus="userName_LostFocus" ></TextBox>
<TextBox x:Name="passwordWatermarked" Height="25" Foreground="Gray" Text="Password" Margin="0,5,0,5" GotFocus="passwordWatermarked_GotFocus"></TextBox>
<PasswordBox x:Name="password" Height="25" PasswordChanged="password_PasswordChanged" KeyUp="password_KeyUp" LostFocus="password_LostFocus" Margin="0,5,0,5" Visibility="Collapsed"></PasswordBox>
<TextBlock x:Name="loginError" Visibility="Hidden" Foreground="Red" FontSize="12"></TextBlock>
</StackPanel>
</DockPanel>
代码是这样的。
private void userNameWatermarked_GotFocus(object sender, RoutedEventArgs e)
{
userNameWatermarked.Visibility = System.Windows.Visibility.Collapsed;
userName.Visibility = System.Windows.Visibility.Visible;
userName.Focus();
}
private void userName_LostFocus(object sender, RoutedEventArgs e)
{
if (string.IsNullOrEmpty(this.userName.Text))
{
userName.Visibility = System.Windows.Visibility.Collapsed;
userNameWatermarked.Visibility = System.Windows.Visibility.Visible;
}
}
private void passwordWatermarked_GotFocus(object sender, RoutedEventArgs e)
{
passwordWatermarked.Visibility = System.Windows.Visibility.Collapsed;
password.Visibility = System.Windows.Visibility.Visible;
password.Focus();
}
private void password_LostFocus(object sender, RoutedEventArgs e)
{
if (string.IsNullOrEmpty(this.password.Password))
{
password.Visibility = System.Windows.Visibility.Collapsed;
passwordWatermarked.Visibility = System.Windows.Visibility.Visible;
}
}
仅仅决定隐藏或显示水印文本框就足够了。虽然不漂亮,但工作得很好。
我决定通过一个行为来解决这个问题。它使用Hint属性定义要显示的文本(如果您愿意,也可以是一个对象),并使用Value属性计算提示是否应该可见。
行为声明如下:
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Interactivity;
using System.Windows.Media;
public class HintBehavior : Behavior<ContentControl>
{
public static readonly DependencyProperty HintProperty = DependencyProperty
.Register("Hint", typeof (string), typeof (HintBehavior)
//, new FrameworkPropertyMetadata(null, OnHintChanged)
);
public string Hint
{
get { return (string) GetValue(HintProperty); }
set { SetValue(HintProperty, value); }
}
public static readonly DependencyProperty ValueProperty = DependencyProperty
.Register("Value", typeof (object), typeof (HintBehavior)
, new FrameworkPropertyMetadata(null, OnValueChanged));
private static void OnValueChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var visible = e.NewValue == null;
d.SetValue(VisibilityProperty, visible ? Visibility.Visible : Visibility.Collapsed);
}
public object Value
{
get { return GetValue(ValueProperty); }
set { SetValue(ValueProperty, value); }
}
public static readonly DependencyProperty VisibilityProperty = DependencyProperty
.Register("Visibility", typeof (Visibility), typeof (HintBehavior)
, new FrameworkPropertyMetadata(Visibility.Visible
//, new PropertyChangedCallback(OnVisibilityChanged)
));
public Visibility Visibility
{
get { return (Visibility) GetValue(VisibilityProperty); }
set { SetValue(VisibilityProperty, value); }
}
public static readonly DependencyProperty ForegroundProperty = DependencyProperty
.Register("Foreground", typeof (Brush), typeof (HintBehavior)
, new FrameworkPropertyMetadata(new SolidColorBrush(Colors.DarkGray)
//, new PropertyChangedCallback(OnForegroundChanged)
));
public Brush Foreground
{
get { return (Brush) GetValue(ForegroundProperty); }
set { SetValue(ForegroundProperty, value); }
}
public static readonly DependencyProperty MarginProperty = DependencyProperty
.Register("Margin", typeof (Thickness), typeof (HintBehavior)
, new FrameworkPropertyMetadata(new Thickness(4, 5, 0, 0)
//, new PropertyChangedCallback(OnMarginChanged)
));
public Thickness Margin
{
get { return (Thickness) GetValue(MarginProperty); }
set { SetValue(MarginProperty, value); }
}
private static ResourceDictionary _hintBehaviorResources;
public static ResourceDictionary HintBehaviorResources
{
get
{
if (_hintBehaviorResources == null)
{
var res = new ResourceDictionary
{
Source = new Uri("/Mayflower.Client.Core;component/Behaviors/HintBehaviorResources.xaml",
UriKind.RelativeOrAbsolute)
};
_hintBehaviorResources = res;
}
return _hintBehaviorResources;
}
}
protected override void OnAttached()
{
base.OnAttached();
var t = (ControlTemplate) HintBehaviorResources["HintBehaviorWrapper"];
AssociatedObject.Template = t;
AssociatedObject.Loaded += OnLoaded;
}
private void OnLoaded(object sender, RoutedEventArgs e)
{
AssociatedObject.Loaded -= OnLoaded;
var label = (Label) AssociatedObject.Template.FindName("PART_HintLabel", AssociatedObject);
label.DataContext = this;
//label.Content = "Hello...";
label.SetBinding(UIElement.VisibilityProperty, new Binding("Visibility") {Source = this, Mode = BindingMode.OneWay});
label.SetBinding(ContentControl.ContentProperty, new Binding("Hint") {Source = this, Mode = BindingMode.OneWay});
label.SetBinding(Control.ForegroundProperty, new Binding("Foreground") {Source = this, Mode = BindingMode.OneWay});
label.SetBinding(FrameworkElement.MarginProperty, new Binding("Margin") {Source = this, Mode = BindingMode.OneWay});
}
}
它用自己的模板包装目标,并向其添加一个标签:
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<ControlTemplate x:Key="HintBehaviorWrapper" TargetType="{x:Type ContentControl}">
<Grid>
<ContentPresenter Content="{TemplateBinding Content}" />
<Label x:Name="PART_HintLabel" IsHitTestVisible="False" Padding="0" />
</Grid>
</ControlTemplate>
</ResourceDictionary>
要使用它,只需将其添加为一个行为并绑定你的值(在我的情况下,我将它添加在一个ControlTemplate中,因此绑定):
<ContentControl>
<i:Interaction.Behaviors>
<behaviors:HintBehavior Value="{Binding Property, RelativeSource={RelativeSource TemplatedParent}}"
Hint="{Binding Hint, RelativeSource={RelativeSource TemplatedParent}}" />
</i:Interaction.Behaviors>
<TextBox ... />
</ContentControl>
如果这是一个干净的解决方案,我希望得到反馈。它不需要静态字典,因此没有内存泄漏。
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"/>
当使用@john-myczek的代码绑定文本框时,我遇到了一些困难。由于TextBox在更新时不会引发焦点事件,水印将在新文本下面保持可见。为了解决这个问题,我简单地添加了另一个事件处理程序:
if (d is ComboBox || d is TextBox)
{
control.GotKeyboardFocus += Control_GotKeyboardFocus;
control.LostKeyboardFocus += Control_Loaded;
if (d is TextBox)
(d as TextBox).TextChanged += Control_TextChanged;
}
private static void Control_TextChanged(object sender, RoutedEventArgs e)
{
var tb = (TextBox)sender;
if (ShouldShowWatermark(tb))
{
ShowWatermark(tb);
}
else
{
RemoveWatermark(tb);
}
}
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