问当IsFocusScope设置为true时，如何在更改后停止控件失去键盘焦点？

EN

public static class FocusExtensions
{
    private static bool SettingKeyboardFocus { get; set; }

    public static bool GetIsEnhancedFocusScope(DependencyObject element) {
        return (bool)element.GetValue(IsEnhancedFocusScopeProperty);
    }

    public static void SetIsEnhancedFocusScope(DependencyObject element, bool value) {
        element.SetValue(IsEnhancedFocusScopeProperty, value);
    }

    public static readonly DependencyProperty IsEnhancedFocusScopeProperty =
        DependencyProperty.RegisterAttached(
            "IsEnhancedFocusScope",
            typeof(bool),
            typeof(FocusExtensions),
            new UIPropertyMetadata(false, OnIsEnhancedFocusScopeChanged));

    private static void OnIsEnhancedFocusScopeChanged(DependencyObject depObj, DependencyPropertyChangedEventArgs e) {
        var item = depObj as UIElement;
        if (item == null)
            return;

        if ((bool)e.NewValue) {
            FocusManager.SetIsFocusScope(item, true);
            item.GotKeyboardFocus += OnGotKeyboardFocus;
        }
        else {
            FocusManager.SetIsFocusScope(item, false);
            item.GotKeyboardFocus -= OnGotKeyboardFocus;
        }
    }

    private static void OnGotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e) {
        if (SettingKeyboardFocus) {
            return;
        }

        var focusedElement = e.NewFocus as Visual;

        for (var d = focusedElement; d != null; d = VisualTreeHelper.GetParent(d) as Visual) {
            if (FocusManager.GetIsFocusScope(d)) {
                SettingKeyboardFocus = true;

                try {
                    d.SetValue(FocusManager.FocusedElementProperty, focusedElement);
                }
                finally {
                    SettingKeyboardFocus = false;
                }

                if (!(bool)d.GetValue(IsEnhancedFocusScopeProperty)) {
                    break;
                }
            }
        }
    }
}