WPF UserControl 检测 LostFocus 忽略儿童

Question

我有一个 UserControl 帽子，其中包含多个元素（ListBoxes、Buttons）和一个带有 ComboBoxes 和 Buttons 的 Popup。

我试过在用户控件上失去焦点，但只要 UserControl 中的焦点发生变化，Lost(Keyboard)Focus 事件就会触发。

但我不想知道一个子项何时将焦点转移到 UserControl 的另一个子项，但我想知道，何时键盘焦点移动到 UserControl 外部的元素并且它是 Popup。

有没有办法在不检查每个元素的 LostFocus 的情况下检测到这一点？

Answer 1

这个解决方案适合你吗？我在 UserControl 中创建了名为 LostFocusIgnoreChildren 的新事件，只有当新的焦点元素不是此 UserControl 的子元素时才会触发。

UserControl1.cs

  public partial class UserControl1 : UserControl
    {
        public UserControl1()
        {
            InitializeComponent();
        }

        public event RoutedEventHandler LostFocusIgnoreChildren;
        private void UserControl_LostFocus(object sender, RoutedEventArgs e)
        {
            var focused_element = FocusManager.GetFocusedElement(Application.Current.Windows.OfType<Window>().SingleOrDefault(x => x.IsActive));
            var parent = (focused_element as FrameworkElement).TryFindParent<UserControl1>();
            if (parent == null && LostFocusIgnoreChildren != null)
                LostFocusIgnoreChildren(this, e);
        }
    }

VisualTreeHelper 扩展

 public static class VisualTreeHelperExt
    {
        public static T TryFindParent<T>(this DependencyObject child)
    where T : DependencyObject
        {
            DependencyObject parentObject = GetParentObject(child);
            if (parentObject == null) return null;
            T parent = parentObject as T;
            if (parent != null)
            {
                return parent;
            }
            else
            {
                return TryFindParent<T>(parentObject);
            }
        }

        public static DependencyObject GetParentObject(this DependencyObject child)
        {
            if (child == null) return null;
            ContentElement contentElement = child as ContentElement;
            if (contentElement != null)
            {
                DependencyObject parent = ContentOperations.GetParent(contentElement);
                if (parent != null) return parent;
                FrameworkContentElement fce = contentElement as FrameworkContentElement;
                return fce != null ? fce.Parent : null;
            }
            FrameworkElement frameworkElement = child as FrameworkElement;
            if (frameworkElement != null)
            {
                DependencyObject parent = frameworkElement.Parent;
                if (parent != null) return parent;
            }
            return VisualTreeHelper.GetParent(child);
        }
    }

Answer 2

这样做更容易：

private void UserControl_LostFocus(object sender, RoutedEventArgs e)
        {
            if (!this.IsKeyboardFocusWithin)
            {
                _lastFocusedElement = e.OriginalSource as IInputElement;
            }
        }

WPF UserControl 检测 LostFocus 忽略儿童

WPF UserControl detect LostFocus ignoring children

c#

wpf

user-controls

focus