progressbar finishes before set maximum amount

问题

I am trying to display downloaded images in tkinter Progressbar, It is working but the progressbar finishes way before the all images are downloaded. I asked a very similar question tkinter updating progress bar on thread progress, My idea is to update progressbar depending on how many files were created using len(os.listdir('.')) to count.

import tkinter
from tkinter.ttk import Progressbar
import os,uuid,requests,threading
import numpy as np

def bar():
    temp = 0
    for lst in chunks:
        threads.append(threading.Thread(target=download_image, args=(lst)))
    for x in threads:
        x.start()
    while temp<len(links):
        progress['value'] = temp
        root.update_idletasks()
        temp =len(os.listdir('.'))
    print("closing threads")
    for i in threads:
        i.join()
    temp =len(os.listdir('.'))
    progress['value'] = temp
    print('done')
    root.destroy()

with open('image_urls.txt','r') as f:
    links = f.read().split('\n') #links to image urls

threads =[]
chunks = [i.tolist() for i in np.array_split(links, 10) if i.size>0]
root = tkinter.Tk()
root.geometry("400x300")
root.title('Downloader v1')
progress = Progressbar(root, orient = tkinter.HORIZONTAL, 
              length = 250, mode = 'determinate',maximum=len(links))
progress.pack(pady = 100)
notice = tkinter.Label(root, text=str(len(links)),
                       fg="grey2",)
notice.place(x=350, y=100)
compose_button = tkinter.Button(root, text = 'Start', command = bar)
compose_button.pack()
root.mainloop()

回答1:

Question: Tkinter Progressbar update from multiple Thread's

Core Point

    .event_generate('<<Progressbar>>')

This example uses a virtual event '<<Progressbar>>' to increment the Progressbar['value']. This event driven progamming, needs, no callback, no polling .after, no queue, to work across Thread's.

---

Imports:

import tkinter as tk
import tkinter.ttk as ttk
import threading, time
import random

The worker Thread

class Task(threading.Thread):
    is_alive = 0

    def __init__(self, app, args, name):
        super().__init__(name=name, daemon=True)
        self.args = args[0]
        self.app = app
        self._lock = threading.Lock()
        self.start()

    def run(self):
        # threaded task
        with self._lock:
            Task.is_alive += 1

        time.sleep(0.01)

        for link in self.args:
            print('Thread[{}]: link:{}'.format(self.name, link))
            time.sleep(random.randint(1, 5))

            with self._lock:
                self.app.event_generate('<<Progressbar>>', when='tail')

        # on end of threaded task
        with self._lock:
            Task.is_alive -= 1
            if Task.is_alive == 0:
                # last Task has finished
                self.app.event_generate('<<COMPLETED>>', when='tail')

Customized Progressbar by inheriting from ttk.Progressbar

class Progressbar(ttk.Progressbar):
    def __init__(self, parent):
        super().__init__(parent, orient="horizontal", 
                         maximum=0, mode="determinate", length=250)
        parent.bind('<<Progressbar>>', self.value)

    def value(self, event):
        self['value'] += 1 

Usage:

class App(tk.Tk):
    def __init__(self):
        super().__init__()

        self.pb = Progressbar(self)
        self.pb.pack()

        tk.Button(self, text="Start", command=self.start).pack()
        self.bind('<<COMPLETED>>', self.on_completed)

    def start(self):
        links = (1, 2, 3, 4, 5, 6, 7, 8, 9)
        self.pb['maximum'] = len(links)
        chunks = [l for l in zip(links[0::3], links[1::3], links[2::3])]

        for i, args in enumerate(chunks, 1):
            # Task start() at once 
            Task(self, name='Task {}'.format(i), args=(args,))

    def on_completed(self, event):
        # Do cleanups before exiting
        self.destroy()


if __name__ == "__main__":
    App().mainloop()

Tested with Python: 3.5 - 'TclVersion': 8.6 'TkVersion': 8.6

来源：https://stackoverflow.com/questions/60670374/progressbar-finishes-before-set-maximum-amount