WPF 在 Button.LostFocus 上触发绑定

Question

我正在设计一个 WPF 应用程序，我想在其中为 window 的默认按钮提供一个标记（例如红色边框）。标记的行为应该是

当没有按钮获得焦点时，标记应该在默认按钮上可见
如果默认按钮获得焦点，那么标记也应该可见
如果任何其他按钮获得焦点，则应隐藏标记

由于我使用的是materialDesign，所以我不得不扩展“MaterialDesignRaisedButton”样式。我写了一个转换器，它将检查 window 中存在的所有按钮，并根据我的要求在默认按钮上设置标记。

internal class ButtonDefaultPropertyConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        bool nonDefaultFocus = false;
        foreach (Button button in FindVisualChildren<Button>((DependencyObject)value))
        {                
            if (button.IsFocused && !button.IsDefault)
            {
                nonDefaultFocus = true;
                break;
            }
        }
        foreach (Button button in FindVisualChildren<Button>((DependencyObject)value))
        {
            if (button.IsDefault)
            {
                if (!nonDefaultFocus)
                    button.BorderBrush = Brushes.Red;
                else
                {
                    button.BorderBrush = (Brush)Application.Current.Resources["PrimaryHueMidBrush"];
                }
            }
            else
            {
                button.BorderBrush = (Brush)Application.Current.Resources["PrimaryHueMidBrush"];
            }
        }
        return 1;
    }

我把触发器写在另一个属性上，只是为了调用转换器。我把它放在 APP.xaml 中，这样我就可以在整个应用程序中使用它。 xaml 看起来像这样

<Style x:Key="MyButton" TargetType="{x:Type Button}">
        <Setter Property="FocusVisualStyle" Value="{StaticResource FocusVisual}"/>
        <Setter Property="Background" Value="{StaticResource PrimaryHueMidBrush}"/>
        <Setter Property="BorderBrush" Value="{StaticResource PrimaryHueMidBrush}"/>
        <Setter Property="Foreground" Value="{StaticResource PrimaryHueLightForegroundBrush}"/>
        <Setter Property="materialDesign:ButtonProgressAssist.IndicatorForeground" Value="{DynamicResource PrimaryHueMidForegroundBrush}" />
        <Setter Property="materialDesign:ButtonProgressAssist.IndicatorBackground" Value="{StaticResource PrimaryHueMidBrush}" />
        <Setter Property="materialDesign:RippleAssist.Feedback" Value="White" />
        <Setter Property="Cursor" Value="Hand"/>
        <Setter Property="materialDesign:ShadowAssist.ShadowDepth" Value="Depth1" />
        <Setter Property="TextBlock.FontWeight" Value="Medium"/>
        <Setter Property="TextBlock.FontSize" Value="14"/>
        <Setter Property="BorderThickness" Value="1"/>
        <Setter Property="HorizontalContentAlignment" Value="Center"/>
        <Setter Property="VerticalContentAlignment" Value="Center"/>
        <Setter Property="Padding" Value="16 4 16 4"/>
        <Setter Property="Height" Value="32" />
        <Setter Property="materialDesign:ButtonProgressAssist.IsIndicatorVisible" Value="False" />
        <Setter Property="materialDesign:ButtonProgressAssist.Opacity" Value=".4" />
        <Setter Property="materialDesign:ButtonAssist.CornerRadius" Value="2" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type Button}">
                    <Grid>
                        <AdornerDecorator CacheMode="{Binding RelativeSource={RelativeSource Self}, Path=(materialDesign:ShadowAssist.CacheMode)}">
                            <Grid>
                                <Border Background="{TemplateBinding Background}" 
                                    CornerRadius="{Binding Path=(materialDesign:ButtonAssist.CornerRadius), RelativeSource={RelativeSource TemplatedParent}}"
                                    BorderThickness="{TemplateBinding BorderThickness}"
                                    BorderBrush="{TemplateBinding BorderBrush}"
                                    x:Name="border" 
                                    Effect="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(materialDesign:ShadowAssist.ShadowDepth), Converter={StaticResource ShadowConverter}}"/>
                                <ProgressBar x:Name="ProgressBar"
                                         Style="{DynamicResource MaterialDesignLinearProgressBar}"
                                         Minimum="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(materialDesign:ButtonProgressAssist.Minimum)}"
                                         Maximum="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(materialDesign:ButtonProgressAssist.Maximum)}"
                                         Foreground="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(materialDesign:ButtonProgressAssist.IndicatorForeground)}"
                                         Background="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(materialDesign:ButtonProgressAssist.IndicatorBackground)}"
                                         Value="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(materialDesign:ButtonProgressAssist.Value)}"
                                         IsIndeterminate="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(materialDesign:ButtonProgressAssist.IsIndeterminate)}"
                                         Visibility="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(materialDesign:ButtonProgressAssist.IsIndicatorVisible), Converter={StaticResource BooleanToVisibilityConverter}}"
                                         Height="{TemplateBinding Height}"
                                         Width="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ButtonBase}}, Path=ActualWidth}"
                                         Opacity="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=(materialDesign:ButtonProgressAssist.Opacity)}"
                                         HorizontalAlignment="Left"
                                         VerticalAlignment="Center">
                                </ProgressBar>
                            </Grid>
                        </AdornerDecorator>
                        <materialDesign:Ripple Content="{TemplateBinding Content}" ContentTemplate="{TemplateBinding ContentTemplate}" Focusable="False"
                                ContentStringFormat="{TemplateBinding ContentStringFormat}"
                                HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                                VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
                                Padding="{TemplateBinding Padding}"
                                SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}">
                            <materialDesign:Ripple.Clip>
                                <MultiBinding Converter="{StaticResource BorderClipConverter}">
                                    <Binding ElementName="border" Path="ActualWidth" />
                                    <Binding ElementName="border" Path="ActualHeight" />
                                    <Binding ElementName="border" Path="CornerRadius" />
                                    <Binding ElementName="border" Path="BorderThickness" />
                                </MultiBinding>
                            </materialDesign:Ripple.Clip>
                        </materialDesign:Ripple>
                    </Grid>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsDefault" Value="True">
                            <Setter Property="BorderThickness" Value="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Window}},Converter={StaticResource ButtonDefaultPropertyConverter}}" />
                        </Trigger>
                        <Trigger Property="IsMouseOver" Value="true">
                            <Setter TargetName="border" Property="materialDesign:ShadowAssist.Darken" Value="True" />
                        </Trigger>
                        <Trigger Property="IsKeyboardFocused" Value="true">
                            <Setter TargetName="border" Property="materialDesign:ShadowAssist.Darken" Value="True" />
                            <Setter Property="BorderThickness" Value="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Window}}, Converter={StaticResource ButtonDefaultPropertyConverter}, UpdateSourceTrigger=Explicit}" />
                        </Trigger>
                        <Trigger Property="IsEnabled" Value="false">
                            <Setter Property="Opacity" Value="0.23"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

按钮看起来像这样

<Button Style="{StaticResource MyButton}" Grid.Row="0" x:Name="btn1" Height="40" Width="100" Content="Button1" IsDefault="True" />
<Button Style="{StaticResource MyButton}" Grid.Row="1" x:Name="btn2" Height="40" Width="100" Content="Button2" />

虽然这几乎达到了我的目的。但唯一的问题是当焦点从按钮上丢失时，转换器就不会被触发。我用谷歌搜索了一下，发现我可以将 EventTriggers 用于 LostFocus 事件。 EventTrigger 的问题是我无法在 EventTriggers 中使用绑定。

所以现在我卡住了。

如果有人能提供帮助，那就太好了...

提前致谢

Answer 1

转换器ButtonDefault属性转换器只能正确处理前两个条件。第三种情况，他不一定总能应付得来。仅当 window 焦点从一个按钮移动到另一个按钮并且没有其他元素具有焦点时，这是正确的。

为了正常操作，转换器必须至少传输所有其他按钮的焦点值。在我看来，使用 Attached 属性.

会更容易实现

Answer 2

您只需将 EventSetter 添加到 Style 并以编程方式处理 LostFocus 事件。

如果Style定义在ResourceDictionary中，您应该添加一个code-behind class并在其中定义事件处理程序。

WPF 在 Button.LostFocus 上触发绑定

WPF Trigger on Button.LostFocus with binding

wpf

eventtrigger

ivalueconverter