Automatically updating a value through a OptionMenu tkinter object

问题

I would like to write a tkinter app that will automatically update a value based on the current state of the OptionMenu object. Here's what I have so far

from tkinter import *
root = Tk()

def show():
  myLabel=Label(root,text=clicked.get()).pack()

clicked=StringVar()
clicked.set("1")

drop = OptionMenu(root,clicked,"1","2","3")
drop.pack()

myButton = Button(root,text="show selection",command=show)

root.mainloop()

In this version, the text can only be updated by clicking a button. How can I make the text update automatically, without this "middle man"?

回答1:

You can simply assign clicked to the textvariable of the Label, then whenever an option is selected, the label will be updated:

import tkinter as tk

root = tk.Tk()

clicked = tk.StringVar(value="1")

drop = tk.OptionMenu(root, clicked, "1", "2", "3")
drop.pack()

tk.Label(root, textvariable=clicked).pack()

root.mainloop()

回答2:

After changing some things, i got it working.

It is better to use the config() function to change item's attributes, and another important thing is to not pack() the objects (the Label, in this case) in the same line that the variable declaration.

Like so, you'll be able to change the text. Here is your code updated!

from tkinter import *

def show():
    myLabel.config(text = clicked.get())

root = Tk()
clicked=StringVar( value="1")

myLabel=Label(root, text="click the button at the bottom to see this label text changed")
myLabel.pack()

drop = OptionMenu(root, clicked, "1","2","3")
drop.pack()

myButton = Button(root, text="show selection", command=show)
myButton.pack()

root.mainloop()

来源：https://stackoverflow.com/questions/63347255/automatically-updating-a-value-through-a-optionmenu-tkinter-object

标签

python

tkinter