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
我已经创建了一个简单的代码实现,它适用于WPF和Silverlight:
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Media;
public class TextBoxWatermarked : TextBox
{
#region [ Dependency Properties ]
public static DependencyProperty WatermarkProperty = DependencyProperty.Register
(
"Watermark",
typeof(string),
typeof(TextBoxWatermarked),
new PropertyMetadata(new PropertyChangedCallback(OnWatermarkChanged))
);
#endregion
#region [ Fields ]
private bool _isWatermarked;
private Binding _textBinding;
#endregion
#region [ Properties ]
protected new Brush Foreground
{
get { return base.Foreground; }
set { base.Foreground = value; }
}
public string Watermark
{
get { return (string)GetValue(WatermarkProperty); }
set { SetValue(WatermarkProperty, value); }
}
#endregion
#region [ .ctor ]
public TextBoxWatermarked()
{
Loaded += (s, ea) => ShowWatermark();
}
#endregion
#region [ Event Handlers ]
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) return;
tbw.ShowWatermark();
}
#endregion
#region [ Methods ]
private void ShowWatermark()
{
if (string.IsNullOrEmpty(base.Text))
{
_isWatermarked = true;
base.Foreground = new SolidColorBrush(Colors.Gray);
var bindingExpression = GetBindingExpression(TextProperty);
_textBinding = bindingExpression == null ? null : bindingExpression.ParentBinding;
if (bindingExpression != null)
bindingExpression.UpdateSource();
SetBinding(TextProperty, new Binding());
base.Text = Watermark;
}
}
private void HideWatermark()
{
if (_isWatermarked)
{
_isWatermarked = false;
ClearValue(ForegroundProperty);
base.Text = "";
SetBinding(TextProperty, _textBinding ?? new Binding());
}
}
#endregion
}
用法:
<TextBoxWatermarked Watermark="Some text" />
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。
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,
...
},
...
}
@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);
}
}
}
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。
<TextBox Grid.Column="0" Name="TextBox_SearchBar" AcceptsReturn="False" AcceptsTab="False" TextWrapping="Wrap" KeyUp="TextBox_SearchBar_KeyUp" />
<TextBox Grid.Column="0" Name="TextBox_Watermark" Text="Search Test Sets" Foreground="Gray" GotFocus="TextBox_Watermark_GotFocus" />
private void TextBox_Watermark_GotFocus( object sender, RoutedEventArgs e ) {
TextBox_Watermark.Visibility = Visibility.Hidden;
TextBox_SearchBar.Focus();
}
这将创建两个文本框,一个用于接收水印的字段,另一个用于水印。接收水印的字段可以是ComboBox或其他控件(只要您获得正确的对齐并相应地获得焦点)。
水印必须是一个文本框或其他控制,可以获得焦点(TextBlock不能获得焦点,因为我学会了艰难的方式)。当水印文本框得到焦点,它隐藏自己,并给予访问其他文本框。
如果你想在搜索栏文本框失去焦点后重新显示水印,只需添加一个LostFocus事件处理程序到TextBox_SearchBar检查输入并切换TextBox_Watermark可见性为隐藏或可见,相应地。
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