使用消息框在循环后跳出 Python

Question

我是 Python 的新手。我这里有这个代码，并试图找到一种方法让消息框跳出 after 循环。有没有办法用我的代码做到这一点，还是我必须以某种方式重写它？

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()

谢谢！

Answer 1

您正在取消对 self.drawBox(...) 的 after 调用，但由于您仍在让 self.updateTimer 运行，循环继续。您应该使用

取消对 self.updateTimer 的下一次调用

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

和

self.after_cancel(self.after_id)

实际上，你让这条路变得更难了。您不需要 updateTimer 函数，也不需要传递那么多变量，只需将它们设为 self 的属性即可。您还在每个循环中创建一个新的 Canvas 和一个新的矩形。这不是必需的，只需更改矩形的颜色即可。

简化代码：

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()

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