tkinter禁用(只读)下拉列表Combobox问题

# 定义下拉列表值
self.Combo3List = [1, 2, 3,]
# 定义下拉列表控件，self.Frame1为Combobox的父级, state表示Combobox的状态，readonly为只读，disabled为禁用
self.Combo3 = Combobox(self.Frame1, values=self.Combo3List, font=("宋体",9), state="readonly")
# 放置控件
self.Combo3.place(relx=0.884, rely=0.627, relwidth=0.053, relheight=0.089)
# 设置Combobox的默认值为Combo3List集合的第一个元素
self.Combo3.set(self.Combo3List[0])

# 设置状态为只读
self.Combo3.configure(state="readonly")
# 设置状态为禁用
#self.Combo3.configure(state="disabled")

import tkinter as tk
root = tk.TK()

# 设置窗口标题
root.title('考试广播系统')
# 设置窗口图标
root.iconbitmap(EXAM_ICON)
# 设置窗口背景色
root.configure(background='#d4d0c8')
# 禁用调整GUI大小
root.resizable(0, 0)
# 获取屏幕宽高
sc_w = self.winfo_screenwidth()
sc_h = self.winfo_screenheight()
# 设置窗口大小
root.geometry(f"560x360+{(sc_w - 560) // 2}+{(sc_h - 360) // 2 - 40}")
# 隐藏窗口，设置后窗口固定
root.overrideredirect(1)

from tkinter import messagebox

def quit_ui():
    if messagebox.askokcancel("退出", "你想退出窗口吗?"):
       self.quit()
       self.destroy()


# 设置窗口属性时一并设置
root.protocol('WM_DELETE_WINDOW', quit_ui)

tk.Button(self, text='登录(L)', width=10, bg="#d4d0c8", command=login_btn).place(x=164, y=300)

tk.Button(self, text='登录(L)', width=10, bg="#d4d0c8", command=lambda: login_btn('l')).place(x=164, y=300)

# 在方法中定义触发事件
root.bind_all('<Control-l>', login_btn)

import Pmw
balloon = Pmw.Balloon(root)
# 创建按钮对象
quit_btn = tk.Button(self, image=take_quit_img, bg="#d4d0c8",
                      command=lambda: _audio_control("quit"))
quit_btn.place(width=30, height=130, x=870, y=382)
balloon.bind(quit_btn, "隐藏控件")

# 这种方式是无法实现赋值的
quit_btn = tk.Button(self, image=take_quit_img, bg="#d4d0c8",
                      command=lambda: _audio_control("quit")).place(width=30, height=130, x=870, y=382)

fwq_var_name = tk.StringVar()
# 输入框设置初始值
fwq_var_name.set("七星耀月")
tk.Entry(root, textvariable=fwq_var_name, width=38, bd=3).place(x=250, y=100)

# 比如为按钮控件添加图片
take_ws_img = tk.PhotoImage('图片所在绝对路径')
sshow_btn = tk.Button(root, image=take_ws_img , bg="#d4d0c8", command=show_other_btn)
show_btn.place(width=50, height=50, x=813, y=13)

# 比如动态更改按钮显示的图片，在config中修改指定参数即可
show_btn.config(image=take_right_img)

km_var_name = tk.StringVar()  # 接收下拉选择的值
SUBJECT_LIST = ("语文", "数学", "英语", "物理", "化学", "地理", "历史")
sub_box = ttk.Combobox(root, textvariable=km_var_name)
sub_box["values"] = SUBJECT_LIST
sub_box.current(0)
sub_box.bind("<<ComboboxSelected>>", get_sub_box)
sub_box.place(width=150, height=24, x=175, y=103)

btn_choose_value = tk.IntVar()
btn_choose_value.set(0)
tk.Radiobutton(root, variable=self.btn_choose_value, bg="#d4d0c8", anchor="n", text="信息提示", value=0, indicatoron=0, command=self.show_or_hide_info).place(x=380, y=336)
tk.Radiobutton(root, variable=self.btn_choose_value, bg="#d4d0c8", text="语音播放内容", alue=1, anchor="n", indicatoron=0, command=self.show_or_hide_info).place(x=488, y=336)

menu_frame = tk.Frame()
frame = tk.LabelFrame(root, labelwidget=menu_frame, bg="white", borderwidth=2, padx=10, pady=8, relief="sunken")
y_bar = tk.Scrollbar(frame, orient="vertical", bd=0, width=14)

list_box = tk.Listbox(frame, bg="white", yscrollcommand=y_bar.set, border=0, highlightthickness=0, selectforeground="blue", selectbackground="#d4d0c8", activestyle="none", font=("微软雅黑", 8), height=4)
y_bar['command'] = list_box.yview
y_bar.pack(side="right", fill="y")
list_box.pack_forget()

info_list_box = tk.Listbox(frame, bg="white", yscrollcommand=y_bar.set, border=0, highlightthickness=0, font=("微软雅黑", 8), height=4)
y_bar['command'] = info_list_box.yview
y_bar.pack(side="right", fill="y")
info_list_box.pack(anchor="nw", fill="both", expand="yes")
info_list_box.insert('end', f"[{time.strftime('%Y-%m-%d %H:%M:%S')}] 启动服务")
info_list_box.insert('end', f"[{time.strftime('%Y-%m-%d %H:%M:%S')}] 更新语音文件成功")

frame.place(width=480, height=124, x=380, y=362)

new_tk = tk.Toplevel()