如何在Tkinter Python中冻结键选项卡的使用

Question

I am trying to make a simple application that scrambles keyboard letters while typing. I am using python along with tkinter. I have a text widget and i need to disable the key tab in my application. I tried it using following code.

text.bind("<Tab>", no_op)

Here no_op is the function given below:

def no_op(self):
    return "break"        

But I am not getting the expected result. I am posting the whole code below.

import Tkinter as tk

def onKeyPress(event):
    first=event.char
    second=ord(first)
    if second==32:
        second=chr(second)
        text.insert('end', '%s' % (second ))
    elif second==8:
        length = len(text.get(1.0, 'end'))
        contents = text.get(1.0, 'end')
        newcon = contents[:-2]
        #text.insert('end', '%s' % (length ))
        text.delete(1.0,'end')
        text.insert('end', '%s' % (newcon ))
    elif(second>=65 and second<=90 or second>=97 and second<=122):
        second=chr(second+3)
        text.insert('end', '%s' % (second ))


def no_op(self):
    return "break"


root = tk.Tk()
root.config(cursor='none')
#root.attributes('-zoomed',True)
text = tk.Text(root, background='white', foreground='black', font=('Comic Sans MS', 12))
text.pack(expand=True,)

text.bind("<Tab>", no_op)
text.bind("<Button-1>", no_op)
text.config(cursor="none")
root.bind('<KeyPress>', onKeyPress)
root.mainloop()

( Note : The problem is that when tab is pressed when some other widget has focus, the text cursor comes in the text area. Then, if I press any letter say,'a' both 'a' and 'd' is inserted to text field. I want to fix that.)

Answer 1

Your problem isn't with the tab key, your problem is focus management. You've made your code work only if the text widget never gets keyboard focus. There are at least two solutions:

• continue down the path of preventing the user from focusing on the text widget
• allow focus on the text widget, and adjust your bindings accordingly

For the first, instead of trying to change the behavior of the tab (and also the shift-tab), you can merely move the focus whenever the text widget gets it. For example:

text.bind("<FocusIn>", lambda event: root.focus_set())

That will prevent the text widget from ever getting focus, and your code should work.

Another solution is to modify your <KeyPress> binding to be on the text widget rather than the root widget, and then simply reject all handling of key presses. That means to do text.bind('<KeyPress>', ...) rather than root.bind... . You then need to modify onKeyPress to return "break" to prevent the default text widget bindings from happening.