TextBox LostFocus does not fire

1
votes

I have a problem with LostFocus event it does not fire when I click on the background.I read some stuff about focus logic and keyboard focus but I could not find a way to get the focus from a control a like textbox when there is only one of them

XAML:

<Grid Height="500" Width="500">
    <TextBox Height="23" Width="120" Margin="12,12,0,0" Name="textBox1" LostFocus="textBox1_LostFocus"  />
</Grid>

C#:

    private void textBox1_LostFocus(object sender, RoutedEventArgs e)
    {

    }
2
c#wpf
anything in this case a grid which is in a window - roah
try to set the background color of your TextBox, to see if it completely covers the grid. If so, you continue clicking on TextBox, by the way. Add another control, to the grid and click on it, in order to make a valid test. - Tigran
@Tigran when I add another textbox and switch to it LostFocus fires and the grid I checked that it is not wrapping the textbox so I am definitly clicking the grid. - roah
You'll have to click on something that actually wants the focus. The grid isn't it. It has no use for keyboard input. - Hans Passant

2 Answers

5
votes

You must use the following tunnelling event : PreviewLostKeyboardFocus on your textbox

Tunneling: Initially, event handlers at the element tree root are invoked. The routed event then travels a route through successive child elements along the route, towards the node element that is the routed event source (the element that raised the routed event). Tunneling routed events are often used or handled as part of the compositing for a control, such that events from composite parts can be deliberately suppressed or replaced by events that are specific to the complete control. Input events provided in WPF often come implemented as a tunneling/bubbling pair. Tunneling events are also sometimes referred to as Preview events, because of a naming convention that is used for the pairs.

0
votes

The following behavior will fix this:

public class TextBoxUpdateOnLostKeyboardFocusBehavior : Behavior<TextBox>
{
    protected override void OnAttached()
    {
        if (AssociatedObject != null)
        {
            base.OnAttached();
            AssociatedObject.LostKeyboardFocus += OnKeyboardLostFocus;
        }
    }

    protected override void OnDetaching()
    {
        if (AssociatedObject != null)
        {
            AssociatedObject.LostKeyboardFocus -= OnKeyboardLostFocus;
            base.OnDetaching();
        }
    }

    private void OnKeyboardLostFocus(object sender, KeyboardFocusChangedEventArgs e)
    {
        var textBox = sender as TextBox;

        if (textBox != null && e.NewFocus == null)
        {
            // Focus on the closest focusable ancestor
            FrameworkElement parent = (FrameworkElement) textBox.Parent;
            while (parent is IInputElement && !((IInputElement) parent).Focusable)
            {
                parent = (FrameworkElement) parent.Parent;
            }

            DependencyObject scope = FocusManager.GetFocusScope(textBox);
            FocusManager.SetFocusedElement(scope, parent);
        }
    }
}

You can attach it to your TextBox as follows:

 <TextBox>
    <i:Interaction.Behaviors>
        <behaviors1:TextBoxUpdateOnLostKeyboardFocusBehavior />
    </i:Interaction.Behaviors>              
</TextBox>