为什么 time.sleep 甚至在 window (tkinter) 打开之前就可以工作？

Question

为什么 time.sleep time.sleep()在 tkinter 的tkinter打开之前起作用？

代码：

import tkinter
import time
window = tkinter.Tk()
window.geometry("500x500")
window.title("Holst")


holst = tkinter.Canvas(window, width = 450, height = 450, bg = "white")
holst.place(x = 25, y = 25)

x = 30
y = 50
d = 30

circle = holst.create_oval(x, y, x+d, y+d, fill = "red")
time.sleep(2)
holst.move(circle, 50, 40)

Answer 1

You asked that why is time.sleep time.sleep() is called before the windows loads because you hopefully called the window.mainloop() at the last of the code which loads the window and keep maintain the tkinter window

The time.sleep time.sleep() function code executes before the window.mainloop() function so it was stop the execution and sleeps before the window could load

一个不错的方法是在if语句中调用time.sleep() 。

Answer 2

Tk 实例要求您运行它的主循环 function 以便控制主进程线程。

您的代码在主进程线程上调用 time.sleep()，这会阻止 GUI 执行任何操作。 如果您希望能够在等待时使用 GUI 执行操作（例如绘制 window、四处移动或绘制其他东西），那么您需要扩展 Tk 以让 UI 使用 self.after 处理回调()

这是一个简单的示例，说明如何扩展 Tk class 以实现您想要的。

import tkinter

class TkInstance(tkinter.Tk):
    def __init__(self):
        tkinter.Tk.__init__(self)

        #Set up the UI here
        self.canvas = tkinter.Canvas(self, width = 450, height = 450, bg = "white")
        self.canvas.place(x = 25, y = 25) #Draw the canvas widget

        #Tell the UI to call the MoveCircle function after 2 seconds
        self.after(2000, self.MoveCircle) #in ms

    def MoveCircle(self):
        x = 30
        y = 50
        d = 30
        circle = self.canvas.create_oval(x, y, x+d, y+d, fill = "red")
        self.canvas.move(circle, 50, 40) #Draw the circle

#Main entrance point
if __name__ == "__main__": #good practice with tkinter to check this
    instance = TkInstance()
    instance.mainloop()