[Tkinter-discuss] 回复： 回复： bind between event and callback

[守株待兔]

code1
from Tkinter import *
root = Tk()
def callback(event):
   print "i am here"

frame = Frame(root, width=100, height=100)

frame.bind("<Key>", callback)
frame.focus_set()
frame.pack()
root.mainloop()

code2
from Tkinter import *
root = Tk()
def callback(event):
   print "i am here"

frame = Frame(root, width=100, height=100)
frame.focus_set()
frame.bind("<Key>", callback)

frame.pack()
root.mainloop()

code1,code2 all can run ,i want to know which one is better?
is it  reasonable that  frame.focus_set() is before frame.bind("<Key>", callback)  or after it?? 
------------------ 原始邮件 ------------------
发件人: "Michael Lange"<klappnase at web.de>;
发送时间: 2011年8月17日(星期三) 下午5:26
收件人: "tkinter-discuss"<tkinter-discuss at python.org>; 

主题: Re: [Tkinter-discuss]回复： bind between event and callback

 
 Hi,

Thus spoketh "守株待兔" <1248283536 at qq.com> 
unto us on Wed, 17 Aug 2011 17:06:28 +0800:

> why in the following code,there is no  "frame.focus_set()" in the
> code ,it can run ,why?? from Tkinter import *
> root = Tk()
> def callback(event):
>    print "i am here"
> 
> frame = Frame(root, width=100, height=100)
> frame.bind("<Button-1>", callback)
> frame.pack()
> root.mainloop()

Mouse events are handled differently than key events.
When you click somewhere in the window of course the window manager
"knows" which widget is clicked - the one under the mouse pointer's "hot
spot". But when you press some key on your keyboard - how would the window
manager "know" which window and which of its child widgets "is meant"?
That is where the "keyboard focus" comes in. Keyboard events are always
sent (by the window manager) to the window that has focus, where
"window" does not only mean a main application window like your Tk()
instannce, but also "child windows" as your Tkinter.Frame() .

I hope this helps

Michael


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