使用消息框突破Python循环后

Question

I'm new to Python. I have this here code and was trying to find a way to have the message box break out of the after loop. Is there a way to do this with my code, or do I have to rewrite it somehow?

from tkinter import *
import random
from tkinter import messagebox

class Example(Frame):
    def __init__(self, parent):
        Frame.__init__(self, parent)
        self.parent = parent
        self.initUI()

    def drawBox(self, canvas):
        color = hex(random.randrange(4095))[2:6]
        l = len(color)
        if l == 1:
            color = '00' + color
        elif l == 2:
            color = '0' + color
        color = '#' + color
        canvas.create_rectangle(100,100,200,200,fill=color)
        canvas.pack()

    def updateTimer(self, canvas, flag, timer):
        timer = self.after(100, lambda: self.drawBox(canvas))
        if flag == True:
            print('OK clicked')
            self.after_cancel(timer)
            return
        else:
            flag = False
            self.after(100, lambda: self.updateTimer(canvas, flag, timer))

    def initUI(self):
        self.parent.title('after_cancel test')
        self.pack(fill=BOTH, expand=1)
        canvas = Canvas(self)
        self.flag = False
        timer = self.after(100, lambda: self.updateTimer(canvas, self.flag, timer))
        if messagebox.askokcancel('Turn that thing off','Click OK to stop'):
            self.updateTimer(canvas, True, timer)

def main():
    root = Tk() 
    root.geometry("300x250+300+300")
    app = Example(root)
    root.mainloop()  

if __name__ == '__main__':
    main()

Thanks!

Answer 1

You're cancelling the after call to self.drawBox(...) , but since you're still letting self.updateTimer run, the loop continues. You should cancel the next call to self.updateTimer with

self.after_id = self.after(100, lambda: self.updateTimer(canvas, flag, timer))

and

self.after_cancel(self.after_id)

---

Actually, you're making this way harder than it is. You don't need the updateTimer function and you defenitely don't need to pass around so many variables, just make them attributes of self . You're also creating a new Canvas and a new rectangle every loop. This is not necessary, simply change the color of the rectangle.

Simplified code:

from tkinter import *
import random
from tkinter import messagebox

class Example(Frame):
    def __init__(self, parent):
        Frame.__init__(self, parent)
        self.parent = parent
        self.initUI()

    def drawBox(self):
        color = hex(random.randrange(4095))[2:6]
        color = '#' + color.zfill(3)
        self.canvas.itemconfig(self.rect, fill=color)
        self.after_id = self.after(100, self.drawBox)

    def initUI(self):
        self.parent.title('after_cancel test')
        self.pack(fill=BOTH, expand=1)
        self.canvas = Canvas(self)
        self.rect = self.canvas.create_rectangle(100,100,200,200,fill='red')
        self.canvas.pack()
        self.drawBox()
        if messagebox.askokcancel('Turn that thing off','Click OK to stop'):
            print('OK clicked')
            self.after_cancel(self.after_id)


def main():
    root = Tk() 
    root.geometry("300x250+300+300")
    app = Example(root)
    root.mainloop()  

if __name__ == '__main__':
    main()