Tkinter focus problem

[Eric Brunel]

Richard Kuhns wrote:

> Well, I'm back again.  This time, though, I actually have working code;
> it's just that I don't understand why some other code doesn't work, and
> I'd really like to.
> 
> Briefly, I want <Return>/<KP_Enter> to function like <Tab> (ie, advance to
> the next widget that will accept focus).  I realize that there are other
> ways to approach this, but I thought this should be fairly straightforward
> to start with. This is for an application where all data will normally be
> entered via the keypad.
> 
> In my data entry widget I have the following:
> 
>     self.bind_all('<Return>', self._nextWin)
> 
>     def _nextWin(self, event):
>         """Make other keys act like <Tab>.
>         """
>         nextwin = self.tk.call('tk_focusNext', event.widget)
>         print "+++focus_next() says", self.tk_focusNext()
>         print "+++call to tk says  ", nextwin
>         self.tk.call('tkTabToWindow', nextwin)
> 
> What I don't understand is why
> "self.tk.call('tk_focusNext', event.widget)"
> and
> "self.tk_focusNext()"
> 
> always return different values.  _nextWin() works like I want the way it's
> written above (minus the prints), but I'd like to know why
> self.tk_focusNext() doesn't.  I think I'm finally beginning to get my
> brain wrapped around Tkinter, but I'm not quite there yet.

Look carefully: the call self.tk.call('tk_focusNext', event.widget) passes 
a widget to the tk command tk_focusNext. The equivalent in Tkinter would 
be to call the method tk_focusNext on event.widget, not on self. 
self.tk_focusNext() returns the widget following self, which is obviously 
not the same than the one following event.widget...

HTH
-- 
- Eric Brunel <eric.brunel at pragmadev.com> -
PragmaDev : Real Time Software Development Tools - http://www.pragmadev.com