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
<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。
其他回答
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;
}
}
namespace PlaceholderForRichTexxBoxInWPF
{
public MainWindow()
{
InitializeComponent();
Application.Current.MainWindow.WindowState = WindowState.Maximized;// maximize window on load
richTextBox1.GotKeyboardFocus += new KeyboardFocusChangedEventHandler(rtb_GotKeyboardFocus);
richTextBox1.LostKeyboardFocus += new KeyboardFocusChangedEventHandler(rtb_LostKeyboardFocus);
richTextBox1.AppendText("Place Holder");
richTextBox1.Foreground = Brushes.Gray;
}
private void rtb_GotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
if (sender is RichTextBox)
{
TextRange textRange = new TextRange(richTextBox1.Document.ContentStart, richTextBox1.Document.ContentEnd);
if (textRange.Text.Trim().Equals("Place Holder"))
{
((RichTextBox)sender).Foreground = Brushes.Black;
richTextBox1.Document.Blocks.Clear();
}
}
}
private void rtb_LostKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
//Make sure sender is the correct Control.
if (sender is RichTextBox)
{
//If nothing was entered, reset default text.
TextRange textRange = new TextRange(richTextBox1.Document.ContentStart, richTextBox1.Document.ContentEnd);
if (textRange.Text.Trim().Equals(""))
{
((RichTextBox)sender).Foreground = Brushes.Gray;
((RichTextBox)sender).AppendText("Place Holder");
}
}
}
}
您可以为输入的文本保留一个单独的值,并且可以在“GotFocus”和“LostFocus”事件中设置文本框的“text”字段。当您获得焦点时,如果没有值,则需要清除文本框。当你失去焦点时,你会想要设置从文本框中获取“文本”值,然后将文本框的“文本”值重置为占位符(如果它是空的)。
private String username = "";
private void usernameTextBox_GotFocus(object sender, RoutedEventArgs e) {
if (String.IsNullOrEmpty(username)) {
usernameTextBox.Text = "";
}
}
private void usernameTextBox_LostFocus(object sender, RoutedEventArgs e) {
username = usernameTextBox.Text;
if (String.IsNullOrEmpty(usernameTextBox.Text)) {
usernameTextBox.Text = "Username";
}
}
然后,您只需确保文本框的“Text”值初始化为占位符文本。
<TextBox x:Name="usernameTextBox" Text="Username" GotFocus="usernameTextBox_GotFocus" LostFocus="usernameTextBox_LostFocus" />
您可以进一步将其提取到扩展“TextBox”类的类中,然后在整个项目中重用它。
namespace UI {
public class PlaceholderTextBox : TextBox {
public String Value { get; set; }
public String PlaceholderText { get; set; }
public Brush PlaceholderBrush { get; set; }
private Brush ValuedBrush { get; set; }
public PlaceholderTextBox() : base() {}
protected override void OnInitialized(EventArgs e) {
base.OnInitialized(e);
ValuedBrush = this.Foreground;
if (String.IsNullOrEmpty(this.Text)) {
this.Text = PlaceholderText;
this.Foreground = PlaceholderBrush;
}
}
protected override void OnGotFocus(System.Windows.RoutedEventArgs e) {
this.Foreground = ValuedBrush;
if (String.IsNullOrEmpty(Value)) {
this.Text = "";
}
base.OnGotFocus(e);
}
protected override void OnLostFocus(System.Windows.RoutedEventArgs e) {
Value = this.Text;
if (String.IsNullOrEmpty(this.Text)) {
this.Text = PlaceholderText;
this.Foreground = PlaceholderBrush;
}
base.OnLostFocus(e);
}
}
}
然后这个可以直接添加到xaml中。
<Window x:Class="UI.LoginWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:m="clr-namespace:UI"
Initialized="Window_Initialized">
<Grid>
<m:PlaceholderTextBox x:Name="usernameTextBox" PlaceholderText="Username" PlaceholderBrush="Gray" />
</Grid>
</Window>
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);
}
}
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"
>
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