WPF：当TextBox具有焦点时，为ListBox设置IsSelected，而不会丢失LostFocus上的选择

Question

I've a ListBox with ListBoxItems with a template so they contain TextBoxes

When the TextBox gets focused I want the ListBoxItem to be selected. One solution I've found looks like this:

<Style TargetType="{x:Type ListBoxItem}">
    <Style.Triggers>
        <Trigger Property="IsKeyboardFocusWithin" Value="True">
            <Setter Property="IsSelected" Value="True"></Setter>
        </Trigger>
    </Style.Triggers>
</Style>

This works great, but when the TextBox loses focus so does the selection.

Is there a way to prevent this from happening?

Answer 1

Best solution I've found to do this with no code behinde is this:

<Style TargetType="{x:Type ListBoxItem}">
    <Style.Triggers>
        <EventTrigger RoutedEvent="PreviewGotKeyboardFocus">
            <BeginStoryboard>
                <Storyboard>
                    <BooleanAnimationUsingKeyFrames
                        Storyboard.TargetProperty="(ListBoxItem.IsSelected)">

                        <DiscreteBooleanKeyFrame KeyTime="0" Value="True"/>
                    </BooleanAnimationUsingKeyFrames>
                </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
    </Style.Triggers>
</Style>

Answer 2

You can also keep focus on the text box, but only have one ListBoxItem selected at any given time, with code behind.

In the ListBox XAML:

<ListBox
PreviewLostKeyboardFocus="CheckFocus">
</ListBox>

Then, in the CheckFocus() method in code-behind:

/* Cause the original ListBoxItem to lose focus
    * only if another ListBoxItem is being selected.
    * If a different element type is selected, the
    * original ListBoxItem will keep focus.
    */
private void CheckFocus(object sender, KeyboardFocusChangedEventArgs e)
{
    // check if focus is moving from a ListBoxItem, to a ListBoxItem
    if (e.OldFocus.GetType().Name == "ListBoxItem" && e.NewFocus.GetType().Name == "ListBoxItem")
    {
        // if so, cause the original ListBoxItem to loose focus
        (e.OldFocus as ListBoxItem).IsSelected = false;
    }
}

Answer 3

From the list of suggested solutions nothing helped me to resolve the same issue. This is the custom solution I made:

1). Create Behavior (class that holds attached properties) that is going to enforce the focus:

public class TextBoxBehaviors
{
    public static bool GetEnforceFocus(DependencyObject obj)
    {
        return (bool)obj.GetValue(EnforceFocusProperty);
    }

    public static void SetEnforceFocus(DependencyObject obj, bool value)
    {
        obj.SetValue(EnforceFocusProperty, value);
    }

    // Using a DependencyProperty as the backing store for EnforceFocus.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty EnforceFocusProperty =
        DependencyProperty.RegisterAttached("EnforceFocus", typeof(bool), typeof(TextBoxBehaviors), new PropertyMetadata(false,
             (o, e) =>
             {
                 bool newValue = (bool)e.NewValue;
                 if (!newValue) return;

                 TextBox tb = o as TextBox;

                 if (tb == null)
                 {
                     MessageBox.Show("Target object should be typeof TextBox only. Execution has been seased", "TextBoxBehaviors warning",
                       MessageBoxButton.OK, MessageBoxImage.Warning);
                 }

                 tb.TextChanged += OnTextChanged;

             }));

    private static void OnTextChanged(object o, TextChangedEventArgs e)
    {
        TextBox tb = o as TextBox;
        tb.Focus();
       /* You have to place your caret at the end of your text manually, because each focus repalce your caret at the beging of text.*/
        tb.CaretIndex = tb.Text.Length;
    }

}

2). Use this behavior in your XAML:

 <DataTemplate x:Key="MyDataTemplate">
    <TextBox behaviors:TextBoxBehaviors.EnforceFocus="True"
             Text="{Binding Path=MyProperty, UpdateSourceTrigger=PropertyChanged}" />
</DataTemplate>