UWP 将 TextBox PlaceholderTextContentPresenter 前景绑定到 UserControl 的 viewmdoel 中的属性

Question

在尝试绑定 TextBox 中 PlaceholderText 的颜色时，我选择尝试将模板放入我可以修改的样式中：

<Style x:Key="TextBoxStyle" TargetType="TextBox">
    <Setter Property="Template">
...
<ContentPresenter x:Name="PlaceholderTextContentPresenter" Foreground="{Binding HintTextColor}" />

我的用户控件：

<UserControl x:Name="This"
    <TextBox
        Style="{StaticResource TextBoxStyle}"
        x:Name="_textBox"
    />
/>

我试过变体：

Foreground="{Binding DataContext.HintTextColor, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}}}}"

也试过了（没有绑定错误）

<ContentPresenter x:Name="PlaceholderTextContentPresenter" Foreground="{Binding ElementName=This.DataContext.HintTextColor}" />

正在尝试将前景连接到正确的 DataContext 和颜色属性，但语法仅在 WPF 中受支持，或者我在输出中遇到绑定错误。如何将前景绑定到控件视图模型 HintTextColor？

编辑

最终的解决方案对我来说是这样的：

<UserControl
    <customControlsUwp:CustomTextBox
        PlaceholderForeground="{Binding HintTextColor, Converter={StaticResource StringColorToBrushConverter}}"
    />
/>

public sealed class CustomTextBox : TextBox {
    public CustomTextBox() {
        DefaultStyleKey = typeof(CustomTextBox);
    }

    private ContentPresenter _placeholderTextContentPresenter;

    public SolidColorBrush PlaceholderForeground {
        get => (SolidColorBrush)GetValue(PlaceholderForegroundProperty);
        set => SetValue(PlaceholderForegroundProperty, value);
    }

    //Add DP PlaceholderForeground for runtime bound changes to HintTextColor
    public static readonly DependencyProperty PlaceholderForegroundProperty =
        DependencyProperty.Register("PlaceholderForeground", typeof(SolidColorBrush), typeof(CustomTextBox), new PropertyMetadata(null, PropertyChangedCallback));


    public static void PropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e) {

        if (!(d is CustomTextBox customTextBox) || !(e.NewValue is SolidColorBrush solidColorBrush))
            return;

        if (customTextBox._placeholderTextContentPresenter == null) 
            customTextBox._placeholderTextContentPresenter.Foreground = solidColorBrush;
    }

    protected override void OnApplyTemplate() { 
        base.OnApplyTemplate();
        _placeholderTextContentPresenter = GetTemplateChild("PlaceholderTextContentPresenter") as ContentPresenter;
    }
}

并在控件样式中添加了模板绑定以捕获第一个值集：

<ContentPresenter x:Name="PlaceholderTextContentPresenter" Foreground="{TemplateBinding PlaceholderForeground}" Grid.ColumnSpan="2" Content="{TemplateBinding PlaceholderText}" IsHitTestVisible="False" Margin="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}" Grid.Row="1" TextWrapping="{TemplateBinding TextWrapping}"/>

Answer 1

UWP 不支持样式绑定。您可以在 MSDN document.

中查看 迁移说明 部分

您可以创建一个自定义文本框并定义一个名为 PlaceholderForeground 的依赖项属性。在其覆盖 OnApplyTemplate 方法中，您可以从其默认样式的模板中获取 "PlaceholderTextContentPresenter" ContentPresenter 控件。然后，当您的依赖项属性更改时，您可以将新值设置为 "PlaceholderTextContentPresenter".Foreground.

public class CustomTextBox : TextBox
{
    private ContentPresenter _PlaceholderTextContentPresenter;

    public SolidColorBrush PlaceholderForeground
    {
        get { return (SolidColorBrush)GetValue(PlaceholderForegroundProperty); }
        set { SetValue(PlaceholderForegroundProperty, value); }
    }

    // Using a DependencyProperty as the backing store for MyProperty.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty PlaceholderForegroundProperty =
        DependencyProperty.Register("PlaceholderForeground", typeof(SolidColorBrush), typeof(CustomTextBox), new PropertyMetadata(null, PropertyChangedCallback));


    public static void PropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if ((d as CustomTextBox)._PlaceholderTextContentPresenter !=null)
        {
            (d as CustomTextBox)._PlaceholderTextContentPresenter.Foreground = e.NewValue as SolidColorBrush;
        }
    }

    protected override void OnApplyTemplate()
    {
        _PlaceholderTextContentPresenter = GetTemplateChild("PlaceholderTextContentPresenter") as ContentPresenter;
    }

    public CustomTextBox()
    {
        DefaultStyleKey = typeof(CustomTextBox);

    }
}

<Application
x:Class="AppUsercontrol.App"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:AppUsercontrol"
RequestedTheme="Light">
<Application.Resources>
    <Style x:Key="CustomTextBoxStyle1" TargetType="local:CustomTextBox">
        <Setter Property="MinWidth" Value="{ThemeResource TextControlThemeMinWidth}"/>
        <Setter Property="MinHeight" Value="{ThemeResource TextControlThemeMinHeight}"/>
        <Setter Property="Foreground" Value="{ThemeResource TextControlForeground}"/>
        <Setter Property="Background" Value="{ThemeResource TextControlBackground}"/>
        <Setter Property="BorderBrush" Value="{ThemeResource TextControlBorderBrush}"/>
        <Setter Property="SelectionHighlightColor" Value="{ThemeResource TextControlSelectionHighlightColor}"/>
        <Setter Property="BorderThickness" Value="{ThemeResource TextControlBorderThemeThickness}"/>
        <Setter Property="FontFamily" Value="{ThemeResource ContentControlThemeFontFamily}"/>
        <Setter Property="FontSize" Value="{ThemeResource ControlContentThemeFontSize}"/>
        <Setter Property="ScrollViewer.HorizontalScrollMode" Value="Auto"/>
        <Setter Property="ScrollViewer.VerticalScrollMode" Value="Auto"/>
        <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Hidden"/>
        <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Hidden"/>
        <Setter Property="ScrollViewer.IsDeferredScrollingEnabled" Value="False"/>
        <Setter Property="Padding" Value="{ThemeResource TextControlThemePadding}"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="local:CustomTextBox">
                    <Grid>
                        <Grid.Resources>
                            <Style x:Name="DeleteButtonStyle" TargetType="Button">
                                <Setter Property="Template">
                                    <Setter.Value>
                                        <ControlTemplate TargetType="Button">
                                            <Grid x:Name="ButtonLayoutGrid" BorderBrush="{ThemeResource TextControlButtonBorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{ThemeResource TextControlButtonBackground}">
                                                <VisualStateManager.VisualStateGroups>
                                                    <VisualStateGroup x:Name="CommonStates">
                                                        <VisualState x:Name="Normal"/>
                                                        <VisualState x:Name="PointerOver">
                                                            <Storyboard>
                                                                <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Background" Storyboard.TargetName="ButtonLayoutGrid">
                                                                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlButtonBackgroundPointerOver}"/>
                                                                </ObjectAnimationUsingKeyFrames>
                                                                <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="BorderBrush" Storyboard.TargetName="ButtonLayoutGrid">
                                                                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlButtonBorderBrushPointerOver}"/>
                                                                </ObjectAnimationUsingKeyFrames>
                                                                <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="GlyphElement">
                                                                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlButtonForegroundPointerOver}"/>
                                                                </ObjectAnimationUsingKeyFrames>
                                                            </Storyboard>
                                                        </VisualState>
                                                        <VisualState x:Name="Pressed">
                                                            <Storyboard>
                                                                <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Background" Storyboard.TargetName="ButtonLayoutGrid">
                                                                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlButtonBackgroundPressed}"/>
                                                                </ObjectAnimationUsingKeyFrames>
                                                                <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="BorderBrush" Storyboard.TargetName="ButtonLayoutGrid">
                                                                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlButtonBorderBrushPressed}"/>
                                                                </ObjectAnimationUsingKeyFrames>
                                                                <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="GlyphElement">
                                                                    <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlButtonForegroundPressed}"/>
                                                                </ObjectAnimationUsingKeyFrames>
                                                            </Storyboard>
                                                        </VisualState>
                                                        <VisualState x:Name="Disabled">
                                                            <Storyboard>
                                                                <DoubleAnimation Duration="0" To="0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="ButtonLayoutGrid"/>
                                                            </Storyboard>
                                                        </VisualState>
                                                    </VisualStateGroup>
                                                </VisualStateManager.VisualStateGroups>
                                                <TextBlock x:Name="GlyphElement" AutomationProperties.AccessibilityView="Raw" Foreground="{ThemeResource TextControlButtonForeground}" FontStyle="Normal" FontSize="12" FontFamily="{ThemeResource SymbolThemeFontFamily}" HorizontalAlignment="Center" Text="&#xE10A;" VerticalAlignment="Center"/>
                                            </Grid>
                                        </ControlTemplate>
                                    </Setter.Value>
                                </Setter>
                            </Style>
                        </Grid.Resources>
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width="*"/>
                            <ColumnDefinition Width="Auto"/>
                        </Grid.ColumnDefinitions>
                        <Grid.RowDefinitions>
                            <RowDefinition Height="Auto"/>
                            <RowDefinition Height="*"/>
                        </Grid.RowDefinitions>
                        <VisualStateManager.VisualStateGroups>
                            <VisualStateGroup x:Name="CommonStates">
                                <VisualState x:Name="Disabled">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="HeaderContentPresenter">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlHeaderForegroundDisabled}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Background" Storyboard.TargetName="BorderElement">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlBackgroundDisabled}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="BorderBrush" Storyboard.TargetName="BorderElement">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlBorderBrushDisabled}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="ContentElement">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlForegroundDisabled}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="PlaceholderTextContentPresenter">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlPlaceholderForegroundDisabled}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="Normal"/>
                                <VisualState x:Name="PointerOver">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="BorderBrush" Storyboard.TargetName="BorderElement">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlBorderBrushPointerOver}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Background" Storyboard.TargetName="BorderElement">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlBackgroundPointerOver}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="PlaceholderTextContentPresenter">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlPlaceholderForegroundPointerOver}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="ContentElement">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlForegroundPointerOver}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="Focused">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="PlaceholderTextContentPresenter">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlPlaceholderForegroundFocused}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Background" Storyboard.TargetName="BorderElement">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlBackgroundFocused}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="BorderBrush" Storyboard.TargetName="BorderElement">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlBorderBrushFocused}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="ContentElement">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="{ThemeResource TextControlForegroundFocused}"/>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="RequestedTheme" Storyboard.TargetName="ContentElement">
                                            <DiscreteObjectKeyFrame KeyTime="0" Value="Light"/>
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                            </VisualStateGroup>
                            <VisualStateGroup x:Name="ButtonStates">
                                <VisualState x:Name="ButtonVisible">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Visibility" Storyboard.TargetName="DeleteButton">
                                            <DiscreteObjectKeyFrame KeyTime="0">
                                                <DiscreteObjectKeyFrame.Value>
                                                    <Visibility>Visible</Visibility>
                                                </DiscreteObjectKeyFrame.Value>
                                            </DiscreteObjectKeyFrame>
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="ButtonCollapsed"/>
                            </VisualStateGroup>
                        </VisualStateManager.VisualStateGroups>
                        <Border x:Name="BorderElement" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" Grid.ColumnSpan="2" Grid.Row="1" Grid.RowSpan="1"/>
                        <ContentPresenter x:Name="HeaderContentPresenter" Grid.ColumnSpan="2" ContentTemplate="{TemplateBinding HeaderTemplate}" Content="{TemplateBinding Header}" Foreground="{ThemeResource TextControlHeaderForeground}" FontWeight="Normal" Margin="0,0,0,8" Grid.Row="0" TextWrapping="{TemplateBinding TextWrapping}" Visibility="Collapsed" x:DeferLoadStrategy="Lazy"/>
                        <ScrollViewer x:Name="ContentElement" AutomationProperties.AccessibilityView="Raw" HorizontalScrollMode="{TemplateBinding ScrollViewer.HorizontalScrollMode}" HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}" IsTabStop="False" IsHorizontalRailEnabled="{TemplateBinding ScrollViewer.IsHorizontalRailEnabled}" IsVerticalRailEnabled="{TemplateBinding ScrollViewer.IsVerticalRailEnabled}" IsDeferredScrollingEnabled="{TemplateBinding ScrollViewer.IsDeferredScrollingEnabled}" Margin="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}" Grid.Row="1" VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}" VerticalScrollMode="{TemplateBinding ScrollViewer.VerticalScrollMode}" ZoomMode="Disabled"/>
                        <ContentPresenter x:Name="PlaceholderTextContentPresenter" Grid.ColumnSpan="2" Content="{TemplateBinding PlaceholderText}" IsHitTestVisible="False" Margin="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}" Grid.Row="1" TextWrapping="{TemplateBinding TextWrapping}"/>
                        <Button x:Name="DeleteButton" AutomationProperties.AccessibilityView="Raw" BorderThickness="{TemplateBinding BorderThickness}" Grid.Column="1" FontSize="{TemplateBinding FontSize}" IsTabStop="False" Margin="{ThemeResource HelperButtonThemePadding}" MinWidth="34" Grid.Row="1" Style="{StaticResource DeleteButtonStyle}" Visibility="Collapsed" VerticalAlignment="Stretch"/>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</Application.Resources>

UWP 将 TextBox PlaceholderTextContentPresenter 前景绑定到 UserControl 的 viewmdoel 中的属性

UWP Binding the TextBox PlaceholderTextContentPresenter Foreground to a property in the UserControl's viewmdoel

c#

templatebinding

uwp-xaml

UWP 将 TextBox PlaceholderTextContentPresenter 前景绑定到 UserControl 的 viewmdoel 中的 属性

UWP Binding the TextBox PlaceholderTextContentPresenter Foreground to a property in the UserControl's viewmdoel

c#

templatebinding

uwp-xaml

UWP 将 TextBox PlaceholderTextContentPresenter 前景绑定到 UserControl 的 viewmdoel 中的属性