画布不显示tex

Question

我的画布以随机变化的颜色显示一个矩形网格，但当我希望它结束时，它不会显示“再见！”我添加到画布上的消息。为什么呢

即使我注释了__init__中的for i in ...行（即首先创建矩形的for循环），我也看不到文本

文本更新在“更新”函数的开始处，在最大迭代次数之后完成

当更改为self.canvas.create_text(100,100, text="Bye Bye!")时，它似乎确实有效。。。但仅当没有显示矩形时

import tkinter as tk
from time import sleep
import random 


class GUI:
    def __init__(self, rows = 10, cols = 10, iteration_timer = 1):        

        self.canv_w = 300
        self.canv_h = 300
        self.cell_w = self.canv_w // cols
        self.cell_h = self.canv_h // rows

        self.master = tk.Tk()
        self.canvas = tk.Canvas(self.master, width = self.canv_w, height = self.canv_h)       
        self.canvas.pack()

        self.rect_dict          = {}
        self.iteration_timer    = iteration_timer
        self.iterations         = 0
        self.MAX_ITER           = 10

        for r in range(rows):
            for c in range(cols):
                self.rect_dict[(r*self.cell_h, c*self.cell_w)]  = self.canvas.create_rectangle(r    *self.cell_h, c    *self.cell_w,
                                                                                               (1+r)*self.cell_h, (1+c)*self.cell_w,
                                                                                               fill="blue")

        self.master.after(iteration_timer, self.update)
        tk.mainloop()



    def update(self):
        if self.iterations >= self.MAX_ITER:
            self.canvas.create_text(0,0,fill="darkblue", font="Times 100 italic bold", text="Bye Bye!")
            sleep(2)
            self.canvas.delete(tk.ALL)
            self.master.destroy()
            return

        self.iterations += 1

        for k in self.rect_dict:
            r = self.rect_dict[k]
            c = random.choice(['yellow', 'red', 'black', 'blue' , 'white'])
            self.canvas.itemconfig(r, fill=c)


        # call again
        self.master.after(self.iteration_timer, self.update)



def main():
    gui = GUI(rows = 20, cols = 20)


if __name__ == "__main__":
    main()

Answer 1

使用time.sleep时，包括Tkinter mainloop在内的所有内容都会停止。Tkinter mainloop负责更新UI，因此，只要您不返回mainloop，您就不会看到UI的任何更新，除非您手动更新它。因为您在sleep之后立即销毁了UI，所以您永远不会看到带有文本的更新UI

基本上可以做两件事，要么在调用sleep之前手动更新，要么将sleep调用更改为after，这将返回到主循环并安排传递给它的函数

要手动更新，请在sleep之前调用self.master.update()

要用after替换sleep，只需更改

sleep(2)
self.canvas.delete(tk.ALL)
self.master.destroy()

到

self.master.after(2000, self.master.destroy)