tkinter菜单“状态”未动态更新

Question

我有一个下拉菜单，其中的选项为state="disabled"，除非列表中包含项目。但是，菜单仅在创建时检查列表，而不是每次用户打开菜单时都检查。如何动态更新状态？

from tkinter import *

window = Tk()
window.title("New Test")
window.geometry("300x300")

my_list = []

root_menu = Menu(window)
window.config(menu=root_menu)

def addList():
    global my_list
    my_list.append("one")
    print(my_list)

def isListEmpty(theList):
    if len(theList) > 0:
        return "active"
    else:
        return "disabled"

def showList():
    global my_list
    print(my_list)

first_menu = Menu(root_menu, tearoff=False)
root_menu.add_cascade(label="File", menu=first_menu)
first_menu.add_command(label="Add to List", command=addList)
first_menu.add_command(label="Show List", state=isListEmpty(my_list), command=showList)

window.mainloop()