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+Tab
ed 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 Window
s 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.
来源:https://stackoverflow.com/questions/18152056/the-difference-between-gotfocus-and-gotkeyboardfocus