WPF验证装饰器 - 仅显示控件之前是否保持焦点

Question

在我的WPF应用程序中,我只希望在用户编辑/输入/聚焦控件之后显示验证装饰器.这样,用户有机会向该字段提供有效输入,并且只有当他们选择不这样做时,才会显示验证.

我们希望鼓励完成每个字段,以便在表单首次打开时指示必填字段可以规避,因为用户将立即倾向于完成他们需要的内容以便摆脱可能也绕过的大红色验证错误形式的流动.

有没有办法知道控件是否已关注？附属财产可能有用吗？

如果它有助于提供更具体的响应:这是我当前的验证样式,显示红色边框[如果控件有边框]和带有错误消息工具提示的小感叹号(非常标准):

<Style TargetType="Control">
    <Style.Triggers>
        <Trigger Property="Validation.HasError" Value="true">
            <Setter Property="ToolTip"
                    Value="{Binding RelativeSource={x:Static RelativeSource.Self},
                    Path=(Validation.Errors).CurrentItem.ErrorContent}"/>

            <Setter Property="Validation.ErrorTemplate">
                <Setter.Value>
                    <ControlTemplate>
                        <DockPanel LastChildFill="true">
                            <Image Source="../Resources/Icons/Error.ico" Margin="4" Width="15" ToolTip="{Binding ElementName=customAdorner, Path=AdornedElement.(Validation.Errors).CurrentItem.ErrorContent}" />
                            <AdornedElementPlaceholder Name="customAdorner" VerticalAlignment="Center" >
                                <Border BorderBrush="red" BorderThickness="1" Visibility="{Binding ElementName=customAdorner, Path=AdornedElement.BorderThickness, Converter={StaticResource hasBorderToVisibilityConverter}}" />
                            </AdornedElementPlaceholder>
                        </DockPanel>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Trigger>
        <Trigger Property="IsVisible" Value="False">
            <Setter Property="Validation.ErrorTemplate" Value="{x:Null}"/>
        </Trigger>
    </Style.Triggers>
</Style>

Answer 1

您可以将附加行​​为与附加属性组合起来执行此操作.Attached Behavior,ObserveFocus将订阅GotFocus事件,并在事件处理程序中将HasHeldFocusAttached Property 设置为True

它可以用于在ViewModel中设置Property,就像这样

<Button local:HasHeldFocusBehavior.ObserveFocus="True"
        local:HasHeldFocusBehavior.HasHeldFocus="{Binding HasHeldFocus, 
                                                          Mode=OneWayToSource}"/>

这里是它如何可以用来改变的例子Background的Button,一旦它一直专注

<Style TargetType="Button">
    <Setter Property="Background" Value="Red"/>
    <Setter Property="local:HasHeldFocusBehavior.ObserveFocus" Value="True"/>
    <Style.Triggers>
        <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self},
                                       Path=(local:HasHeldFocusBehavior.HasHeldFocus)}"
                        Value="True">
            <Setter Property="Background" Value="Green"/>
        </DataTrigger>
    </Style.Triggers>
</Style>

HasHeldFocusBehavior

public static class HasHeldFocusBehavior
{
    public static readonly DependencyProperty ObserveFocusProperty =
        DependencyProperty.RegisterAttached("ObserveFocus",
                                            typeof(bool),
                                            typeof(HasHeldFocusBehavior),
                                            new UIPropertyMetadata(false, OnObserveFocusChanged));
    public static bool GetObserveFocus(DependencyObject obj)
    {
        return (bool)obj.GetValue(ObserveFocusProperty);
    }
    public static void SetObserveFocus(DependencyObject obj, bool value)
    {
        obj.SetValue(ObserveFocusProperty, value);
    }
    private static void OnObserveFocusChanged(DependencyObject dpo,
                                              DependencyPropertyChangedEventArgs e)
    {
        UIElement element = dpo as UIElement;
        element.Focus();
        if ((bool)e.NewValue == true)
        {
            SetHasHeldFocus(element, element.IsFocused);
            element.GotFocus += element_GotFocus;
        }
        else
        {
            element.GotFocus -= element_GotFocus;
        }
    }
    static void element_GotFocus(object sender, RoutedEventArgs e)
    {
        UIElement element = sender as UIElement;
        SetHasHeldFocus(element, true);
    }

    private static readonly DependencyProperty HasHeldFocusProperty =
        DependencyProperty.RegisterAttached("HasHeldFocus",
                                            typeof(bool),
                                            typeof(HasHeldFocusBehavior),
                                            new UIPropertyMetadata(false));
    public static void SetHasHeldFocus(DependencyObject element, bool value)
    {
        element.SetValue(HasHeldFocusProperty, value);
    }
    public static bool GetHasHeldFocus(DependencyObject element)
    {
        return (bool)element.GetValue(HasHeldFocusProperty);
    }
}

更新

在您的情况下,您可以Validation.HasError使用MultiTrigger 替换Trigger

<Style TargetType="Control">
    <Style.Triggers>
        <MultiDataTrigger>
            <MultiDataTrigger.Conditions>
                <Condition Binding="{Binding RelativeSource={RelativeSource Self},
                                             Path=(Validation.HasError)}"
                           Value="True"/>
                <Condition Binding="{Binding RelativeSource={RelativeSource Self},
                                             Path=(local:HasHeldFocusBehavior.HasHeldFocus)}"
                           Value="True"/>
            </MultiDataTrigger.Conditions>
            <!-- Setters.. -->
        </MultiDataTrigger>
        <!-- ... -->
    </Style.Triggers>
</Style>