如何使用相同的按钮停止/暂停和重新启动代码？ (tkinter)

Question

This is a photo slideshow code its just a skeleton I want use buttons to start or stop the code from slide show.

# import required modules
import tkinter as tk
from tkinter import *
from PIL import Image
from PIL import ImageTk

# This here is to adjust window
root=tk.Tk()
root.geometry("200x200")

# loading the images
img=ImageTk.PhotoImage(Image.open("photo1.png"))
img2=ImageTk.PhotoImage(Image.open("photo2.png"))
img3=ImageTk.PhotoImage(Image.open("photo3.png"))
img4=ImageTk.PhotoImage(Image.open("photo4.png"))
l=Label()
l.pack()

# using recursion to slide to next image
x = 1
# function to change to next image
def move():
    global x
    if x == 4:
        x = 1
    if x == 1:
        l.config(image=img)
    elif x == 2:
        l.config(image=img2)
    elif x == 3:
        l.config(image=img3)
    x = x+1
   root.after(2000, move)

# calling the function please refer the indents
btn_1 = Button(root, text="start", command=move)
btn_1.pack()

btn_2=Button(root,text="start", command=pause))
btn_2.pack()
root.mainloop()

Answer 1

Here's runnable code that illustrates how to do it. It uses several global variables to keep track of the current state of the slide show that the various functions use to determine what needs to be be done.

It simplies the logic you had for determining the next image to display by adding one to then current image index and the applying the modulo % the number of images in show which forces the index back to 0 whenever it exceeds the number of image that there are — which can all be done with a single statement: cur_img = (cur_img+1) % len(slides) .

You could get rid of the most of the globals by defining a SlideShow class that encapsulated the state variables and defined the related functions that manipulate them.

from pathlib import Path
from PIL import Image
from PIL import ImageTk
import tkinter as tk


root = tk.Tk()
root.geometry("500x500")

after_id = None
cur_img = 0
paused = True

image_folder = Path('./photos')

slides = [ImageTk.PhotoImage(Image.open(filename))
            for filename in image_folder.glob('*.png')]

def slide_show():
    """Change to next image (wraps around)."""
    global after_id, cur_img, paused

    if not paused:
        cur_img = (cur_img+1) % len(slides)
        lbl.config(image=slides[cur_img])

    after_id = root.after(2000, slide_show)

def start():
    global after_id, cur_img, paused

    paused = False
    if after_id:  # Already started?
        root.after_cancel(after_id)
        after_id = None

    slide_show()

def pause():
    global after_id, cur_img, paused

    paused = True


lbl = tk.Label(image=slides[cur_img])
lbl.pack()

btn_1 = tk.Button(root, text="start", command=start)
btn_1.pack()

btn_2 = tk.Button(root, text="pause", command=pause)
btn_2.pack()

root.mainloop()