无法向Tkinter Python中的Treeview添加项目

import tkinter as tk
from tkinter import ttk

def add_item():
    item_text = entry.get()
    tree.insert('', 'end', text=item_text)

root = tk.Tk()

# 创建Treeview
tree = ttk.Treeview(root)
tree.pack()

# 添加列
tree['columns'] = ('column1')
tree.column('#0', width=100)
tree.column('column1', width=100)

# 添加列标题
tree.heading('#0', text='Item')
tree.heading('column1', text='Column 1')

# 添加项目
tree.insert('', 'end', text='Item 1', values=('Value 1'))

# 添加按钮和输入框
entry = tk.Entry(root)
entry.pack()
button = tk.Button(root, text='Add Item', command=add_item)
button.pack()

root.mainloop()