显示tkinter.simpledialog提示后，Tkinter文本小部件不可用

import tkinter as tk
from tkinter import simpledialog

class CustomDialog(tk.Toplevel):
    def __init__(self, parent):
        super().__init__(parent)
        self.title("Custom Dialog")
        
        self.entry = tk.Entry(self)
        self.entry.pack()
        
        self.button = tk.Button(self, text="OK", command=self.on_ok)
        self.button.pack()
        
    def on_ok(self):
        value = self.entry.get()
        self.master.update_text(value)
        self.destroy()

class MainApplication(tk.Tk):
    def __init__(self):
        super().__init__()
        self.title("Main Application")
        
        self.text = tk.Text(self)
        self.text.pack()
        
        self.button = tk.Button(self, text="Show Dialog", command=self.show_dialog)
        self.button.pack()
        
    def show_dialog(self):
        dialog = CustomDialog(self)
        value = simpledialog.askstring("Input", "Enter a value:")
        self.update_text(value)
        
    def update_text(self, value):
        self.text.insert(tk.END, value + "\n")

if __name__ == "__main__":
    app = MainApplication()
    app.mainloop()