如何在后面的代码中添加到画布中的用户控件

import tkinter as tk

def on_click():
    print("Button clicked!")

button = tk.Button(text="Click me", command=on_click)

canvas.create_window(100, 100, anchor=tk.NW, window=button)

import tkinter as tk

def on_click():
    print("Button clicked!")

root = tk.Tk()

canvas = tk.Canvas(root, width=400, height=400)
canvas.pack()

button = tk.Button(text="Click me", command=on_click)
canvas.create_window(100, 100, anchor=tk.NW, window=button)

root.mainloop()