The difference between GotFocus and GotKeyboardFoc

问题:

What is the difference(s) between GotFocus and GotKeyboardFocus -and similarly LostFocus and LostKeyboardFocus?

Sorry for the simple question, but, I googled it and read a lot of blog posts, but I'm still confused. It seems nobody knows exactly what is the difference ):

UPDATE:

My usage:

I am creating a custom control by extending Control class. Something like ComboBox but with some other effects. I'm trying to open and close a Popup by setting a property: IsDropDownOpen just like a ComboBox through the GotFocus and LostFocus events. I don't want to Popup get closed, when I Alt+Tabed the windows, but get closed when I click on a Button for example or I go to a TextBox. I did:

private static void OnGotFocusHandler(object sender, RoutedEventArgs e) {
    if (e.Handled)
        return;
    ((SearchBox)sender).IsDropDownOpen = true;
    e.Handled = true;
}

private static void OnLostFocusHandler(object sender, RoutedEventArgs e) {
    if (e.Handled)
        return;
    ((SearchBox)sender).IsDropDownOpen = false;
    e.Handled = true;
}

The GotFocus works. But the Lost one didn't. If I do the Lost stuff in LostKeyboardFocus then when I Alt+Tab the windows, or Window goes to inactive, then the method get called, while I don't want. How can I solve it?

回答1:

MSDN has an overview of focus, but I'll try to explain it here.

WPF has 2 concepts regarding focus. There is the physical keyboard focus, and there is logical focus. Only one element can have keyboard focus (and if the application isn't the active application, no element will have keyboard focus).

Multiple items can have logical focus. In fact, you can create new "focus scopes". As per MSDN:

When keyboard focus leaves a focus scope, the focused element will lose keyboard focus but will retain logical focus. When keyboard focus returns to the focus scope, the focused element will obtain keyboard focus. This allows for keyboard focus to be changed between multiple focus scopes but ensures that the focused element in the focus scope regains keyboard focus when focus returns to the focus scope.

You can define your own focus scope on an element (typically a Panel) by setting FocusManager.IsFocusScope="True". The controls in WPF that are focus scopes by default are Window, MenuItem, ToolBar, and ContextMenu.

This makes sense if you think about having multiple Windows in your application. When you Alt-Tab between them, you expect your keyboard focus to return to the same place it was the last time the Window had focus. By keeping keyboard focus and logical focus separate, you can achieve this.