ttk组合框列表值在alt-Tab键切换后保持打开状态

import tkinter as tk
from tkinter import ttk

def on_combobox_focus(event):
    combobox['postcommand']()

root = tk.Tk()

combobox = ttk.Combobox(root)
combobox['values'] = ['Option 1', 'Option 2', 'Option 3']
combobox.bind('<FocusIn>', on_combobox_focus)
combobox.pack()

root.mainloop()

import tkinter as tk
from tkinter import ttk

def on_combobox_focus(event):
    combobox['state'] = 'readonly'

root = tk.Tk()

selected_option = tk.StringVar()

combobox = ttk.Combobox(root, textvariable=selected_option)
combobox['values'] = ['Option 1', 'Option 2', 'Option 3']
combobox.bind('<FocusIn>', on_combobox_focus)
combobox.pack()

root.mainloop()