在tkinter中创建后退按钮？

Question

I have a button, encrypt_button , which destroys what was originally on the screen and displays something new under def encrypt() . I want to create a back button which can restore what was on a previous screen after it has been destroyed. I have tried the following which does not destroy what is under def encrypt() and if you click the button again, the original labels will not be destroyed either.

import tkinter

window = tkinter.Tk()
entry = tkinter.Entry(window)

def encrypt():
    encrypt_label = tkinter.Label(window, text="Please enter the message you'd like to encrypt", font=('Helvetica', 14))
    encrypt_label.pack()
    entry = tkinter.Entry(window)
    entry.pack()
    encrypt_confirm = tkinter.Button(window, text="Confirm")
    encrypt_confirm.pack()
    back_button = tkinter.Button(window, text="Back", command=back)
    back_button.pack()
    encrypt_button.destroy()
    title_header.destroy() 
    title_label.destroy()
    heading_label.destroy()

def back():
    title_header = tkinter.Label(window, text="ENCRYPTION/DECRYPTION", font=('Helvetica', 16))
    title_header.pack()
    title_label = tkinter.Label(window, text="Welcome to this encryption and decryption program")
    title_label.pack()
    heading_label = tkinter.Label(window, text="When you are ready, press a button to continue")
    heading_label.pack()
    encrypt_button = tkinter.Button(window, text="Encrypt", command=encrypt)
    encrypt_button.pack()
    encrypt_label.destroy()
    entry.destroy()
    encrypt_confirm.destroy()
    back_button.destroy()

title_header = tkinter.Label(window, text="ENCRYPTION/DECRYPTION", font=('Helvetica', 16))
title_header.pack()

title_label = tkinter.Label(window, text="Welcome to this encryption and decryption program")
title_label.pack()

heading_label = tkinter.Label(window, text="When you are ready, press a button to continue")
heading_label.pack()

encrypt_button = tkinter.Button(window, text="Encrypt", command=encrypt)
encrypt_button.pack()

encrypt_label = tkinter.Label(window, text="Please enter the message you'd like to encrypt", font=('Helvetica', 14))

entry = tkinter.Entry(window)

encrypt_confirm = tkinter.Button(window, text="Confirm")

back_button = tkinter.Button(window, text="Back", command=back)

window.mainloop()

I have also tried without defining each label and button but that doesn't work either. (Obviously I'd get the x is not defined error)

Answer 1

The problem in your code is that all of your variables are local variables, so they are only visible in the function that creates them.

The simplest solution is to make each "page" be a frame. Make sure the handle to that frame is global, or an instance attribute if you're using classes.

Once you have that, simply delete the frame for the current page and recreate the frame for the other page. When you delete the frame, any children will also automatically get deleted.