文字preVIEW的文本框 [英] TextPreview for Textbox

问题描述

返工问题澄清我的需要：

我想一个preVIEW文本添加到文本框时，他们内心空虚，就像有些人可能从知道Xamarin 。

I want to add a preview Text to Textboxes when they're empty, just like some of you may know it from Xamarin.

我发现在 SO 这个答案。

这是风格从我上面链接了答案。

This is the Style from the Answer I linked above.

<TextBlock Grid.Row="5"
           Grid.Column="1"
           VerticalAlignment="Center"
           Text="Username:">
</TextBlock>
<TextBox Grid.Row="5"
         Grid.Column="3">
    <TextBox.Style>
         <Style TargetType="TextBox">
             <Style.Resources>
                 <VisualBrush x:Key="CueBannerBrush" AlignmentX="Left" AlignmentY="Center" Stretch="None">
                       <VisualBrush.Visual>
                            <Label Content="Test" Foreground="LightGray" />
                       </VisualBrush.Visual>
                 </VisualBrush>
             </Style.Resources>
             <Style.Triggers>
                <Trigger Property="Text" Value="{x:Static sys:String.Empty}">
                     <Setter Property="Background" Value="{StaticResource CueBannerBrush}" />
                </Trigger>
                <Trigger Property="Text" Value="{x:Null}">
                     <Setter Property="Background" Value="{StaticResource CueBannerBrush}" />
                </Trigger>
                <Trigger Property="IsKeyboardFocused" Value="True">
                     <Setter Property="Background" Value="White" />
                </Trigger>
             </Style.Triggers>
         </Style>
    </TextBox.Style>
</TextBox>

我得到以下结果：

I get the following result:

由于这是很好的工作我想它在窗口适用于每个文本框。
所以，我的方法是改变这一行：
＆LT;标签内容=测试前景=浅灰色/＆GT;

Since this is working nicely I want to apply it to every TextBox in that Window. So my approach was to change this line: <Label Content="Test" Foreground="LightGray" />

我想，也许将其更改为＆LT;标签内容=测试前景=浅灰色/＆GT; 会做的伎俩，但它不能正常工作

I thought maybe changing it to <Label Content="Test" Foreground="LightGray" /> would do the trick, but it is not working.

我想这件事情与标签属性和键入它（对象而不是字符串）。

I guess it's something with the Tag Property and the Type of it (object instead of string).

由于第一种方法是工作般的魅力我真的不明白为什么我应该需要为自定义控件...

Since the first approach is working like charm I don't really see why I should need a custom control for that...

所以，我试过那么是这样的：

So what I tried then is this:

 <Window.Resources>
    <Style TargetType="TextBox">
        <Style.Resources>
            <VisualBrush x:Key="CueBannerBrush" AlignmentX="Left" AlignmentY="Center" Stretch="None">
                <VisualBrush.Visual>
                    <Label Content="{Binding RelativeSource={RelativeSource Self}, Path=Tag}" Foreground="LightGray" />
                </VisualBrush.Visual>
            </VisualBrush>
        </Style.Resources>
        <Style.Triggers>
            <Trigger Property="Text" Value="{x:Static sys:String.Empty}">
                <Setter Property="Background" Value="{StaticResource CueBannerBrush}" />
            </Trigger>
            <Trigger Property="Text" Value="{x:Null}">
                <Setter Property="Background" Value="{StaticResource CueBannerBrush}" />
            </Trigger>
            <Trigger Property="IsKeyboardFocused" Value="True">
                <Setter Property="Background" Value="White" />
            </Trigger>
        </Style.Triggers>
    </Style>
</Window.Resources>

我缺少什么 - 为什么是不是工作？

What am I missing - why isn't that working ?

推荐答案

有关的可重复使用的文本框，你需要创建一个自定义的控制。也为多年平均值的结合具有视觉刷工作得很好，所以你需要一些临时对象存储的值。请参阅我的下面code。

For the reusable textbox, you need to create a custom control. Also for binding doesnot work well with visual brush, so you need some temp object to store the value. Refer my below code.

 <Window x:Class="ChkList_Learning.Window4"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:ChkList_Learning"
        xmlns:sys="clr-namespace:System;assembly=mscorlib"
        mc:Ignorable="d"
        Title="Window4" Height="300" Width="300">
    <Window.Resources>
        <local:Temp x:Key="temp" Value="{Binding ElementName=Hostname, Path=Watermark}"/>
        <Style TargetType="{x:Type local:WatermarkTextBox}" BasedOn="{StaticResource {x:Type TextBox}}">
            <Style.Resources>
                <VisualBrush x:Key="WatermarkBrush" AlignmentX="Left" AlignmentY="Center" Stretch="None">
                    <VisualBrush.Visual>
                        <TextBlock Text="{Binding Source={StaticResource temp}, Path=Value}" FontFamily="Segoe UI" FontSize="20" Foreground="LightGray" Padding="5" />
                    </VisualBrush.Visual>
                </VisualBrush>
            </Style.Resources>
            <Style.Triggers>
                <Trigger Property="Text" Value="{x:Static sys:String.Empty}">
                    <Setter Property="Background" Value="{StaticResource WatermarkBrush}" />
                </Trigger>
                <Trigger Property="Text" Value="{x:Null}">
                    <Setter Property="Background" Value="{StaticResource WatermarkBrush}" />
                </Trigger>
                <Trigger Property="IsKeyboardFocused" Value="True">
                    <Setter Property="Background" Value="White" />
                </Trigger>
            </Style.Triggers>
        </Style>
    </Window.Resources>
    <Grid>
        <local:WatermarkTextBox x:Name="Hostname" Height="40" FontFamily="Segoe UI" FontSize="20" VerticalContentAlignment="Center" Watermark="Hello, world.">

        </local:WatermarkTextBox>
    </Grid>
</Window>

     public class Temp : Freezable
        {

            // Dependency Property
            public static readonly DependencyProperty ValueProperty =
                 DependencyProperty.Register("Value", typeof(string),
                 typeof(Temp), new FrameworkPropertyMetadata(string.Empty));

            // .NET Property wrapper
            public string Value
            {
                get { return (string)GetValue(ValueProperty); }
                set { SetValue(ValueProperty, value); }
            }

            protected override System.Windows.Freezable CreateInstanceCore()
            {
                return new Temp();
            }
        }
 public class WatermarkTextBox : TextBox
    {
        static WatermarkTextBox()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(WatermarkTextBox), new FrameworkPropertyMetadata(typeof(WatermarkTextBox)));
        }

        public static readonly DependencyProperty WatermarkProperty = DependencyProperty.Register("Watermark", typeof(string), typeof(WatermarkTextBox));

        public string Watermark
        {
            get { return (string)GetValue(WatermarkProperty); }
            set { SetValue(WatermarkProperty, value); }
        }
    }

这篇关于文字preVIEW的文本框的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！