在Caliburn Micro中单击背景时，TextBox是否有办法失去焦点？

Question

When trying to rebuild a WPF Application to use Caliburn Micro I experienced that a TextBox does not loose focus when you click outside of it. Is there a fix for that behaviour?

I am using Caliburn Micro 3.2.0. I tried using older versions but this problem persits.

XAML:

<Window x:Class="WPFUI.Views.ShellView"
        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:WPFUI.Views"
        xmlns:cal="http://www.caliburnproject.org"
        mc:Ignorable="d"
        Title="ShellView" Height="450" Width="800">
    <Grid>
        ...
        <WrapPanel>
            <TextBox x:Name="Name"  MinWidth="50"  
                     cal:Message.Attach="[Event LostFocus] = [Action Name_LostFocus()];
                     [Event PreviewTextInput] = [Action Name_PreviewTextInput($source, $eventArgs)]">
            </TextBox>
            ...
        </WrapPanel>
        ...
    </Grid>
</Window>

Answer 1

I assume this is a case where you do not have any other Element in the Window other than the Textbox, which is why it cannot lose focus. One way to achieve this is to make the Window Focusable and setting Focus to it using a behavior.

For Example, assuming your Xaml to be as follows

<Window x:Class="CM.WPFApp2019.Views.ShellView"
        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:cal="http://www.caliburnproject.org"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:CM.WPFApp2019.Views"
        xmlns:i = "http://schemas.microsoft.com/expression/2010/interactivity" 
        xmlns:behaviors="clr-namespace:CM.WPFApp2019.ViewModels"
        mc:Ignorable="d" Focusable="True"
        Title="ShellView" Height="450" Width="800">
    <i:Interaction.Behaviors>
        <behaviors:ClearFocusOnClickBehavior ElementToClearFocus="{Binding ElementName=Name}"/>
    </i:Interaction.Behaviors>
    <Grid>
        <WrapPanel>
            <TextBox x:Name="Name"  MinWidth="50"  Focusable="True"
                     cal:Message.Attach="[Event LostFocus] = [Action Name_LostFocus()];
                     [Event PreviewTextInput] = [Action Name_PreviewTextInput($source, $eventArgs)]">
            </TextBox>
        </WrapPanel>
    </Grid>
</Window>

Please note I have added a Behavior called ClearFocusOnClickBehavior to the Window. Also you have set the Focusable Property of Window to be true.

Now you can define the behavior as follows

public class ClearFocusOnClickBehavior : Behavior<FrameworkElement>
    {
        public static readonly DependencyProperty ElementToClearFocusProperty = DependencyProperty.RegisterAttached("ElementToClearFocus", typeof(FrameworkElement), 
                                                                            typeof(ClearFocusOnClickBehavior), new UIPropertyMetadata());


        public FrameworkElement ElementToClearFocus
        {
            get { return (FrameworkElement)GetValue(ElementToClearFocusProperty); }
            set { SetValue(ElementToClearFocusProperty, value); }
        }
        protected override void OnAttached()
        {
            AssociatedObject.MouseDown += (sender, args) => 
            {
                FrameworkElement ctrl = ElementToClearFocus; 
                FrameworkElement parent = (FrameworkElement)ElementToClearFocus.Parent;

                while (parent != null && parent is IInputElement
                                  && !((IInputElement)parent).Focusable)
                {
                    parent = (FrameworkElement)parent.Parent;
                }

                DependencyObject scope = FocusManager.GetFocusScope(ElementToClearFocus); 
                FocusManager.SetFocusedElement(scope, parent as IInputElement);
            };
            base.OnAttached();
        }

    }

The Behavior would add a MouseDown event for the associated object, where you could trace the Parent of the ElementToClearFocus Control which can be Focused. In this case, since you have set the Window as focusable, it would receive the Focus. The Textbox in turn loses the focus and raises the Name_LostFocus method