Tkinter 滞后于“更新”命令

Question

I made a timer just to test something out. and for some reason it starts lagging, here is the timer:

from tkinter import *
from time import sleep

main = Tk()
main.title("Timer")

c = Canvas(main,width=1000,height=400)
c.pack()
c.config(bg="black")

hours = -1

while True:
    hours += 1
    for minutes in range(60):
        for seconds in range(60):
            c.create_rectangle(0,0,1000,400,fill="black")
            c.create_text(500,200,text=(str(hours)+":"+str(minutes)+":"+str(seconds)),font=("",200),fill="white")
            c.update()
            sleep(1)

Can someone figure out where it happens? I noticed I can run the timer without tkinter and just with print , but I need to use tkinter for other projects too.

Answer 1

You are creating text widgets covered by black rectangles in succession, without ever removing them - in essence, every second, you are piling two more canvas items on top of all the previous ones!

The correct approach is to use the tkinter.mainloop in conjunction with the tkinter.after method, and steer clear from using a while loop, and tkinter.update . You can change the text displayed by a canvas text item using itemconfigure .

The use of time.sleep in a GUI is a recipe to have your GUI stop responding to interactions - don't do that!

Maybe do this instead:

import tkinter as tk


def update_clock():
    clock_text = f'{hours}:{str(minutes).zfill(2)}:{str(seconds).zfill(2)}'
    canvas.itemconfigure(clock, text=clock_text)
    main.after(1000, _increment_time)


def _increment_time():
    global clock, hours, minutes, seconds
    seconds += 1
    if seconds == 60:
        seconds = 0
        minutes += 1
    if minutes == 60:
        minutes = 0
        hours += 1
    update_clock()
    

main = tk.Tk()
main.title('Timer')

canvas = tk.Canvas(main, width=1000, height=400, bg='black')
canvas.pack()

hours, minutes, seconds = 0, 0, 0
clock = canvas.create_text(500, 200, font=('', 200), fill='white')
update_clock()

main.mainloop()