ttk进度条冻结

Question

I want a progress bar that shows the user the download progress. When updating the GUI and downloading at the same time the progress bar freezes, and I understand why but I don't know how to solve it. I tried multithreading using this post: Tkinter: How to use threads to preventing main event loop from “freezing” and using The Basics of Python Multithreading and Queues as a guid to help me fit it to my needs. The problem is that which way I try to achieve my goal, I always seem to make a mistake when changing it to do what I need it to do.

The most basic version of my code (without multithreading):

from Tkinter import *
import ttk
from urllib import URLopener # Downloading files 

# Make frame to tell user what file is getting downloaded
self.Progressmsg = Label(self, text="TempValue")
self.Progressmsg.pack(pady=(10,0))

# Make progress bar to show user download progress
self.Progressbar = ttk.Progressbar(self, mode="determinate", orient='horizontal', lengt=280, maximum=len(self.AllClasses))
self.Progressbar.pack(padx=10, pady=10)
self.Progressbar["value"] = 0

def DownloadFile(Class):
    # Update progress message
    self.Progressmsg["text"] = "Downloading {0}.ics...".format(Class)

    # Download each file from saxion website
    CalFile = URLopener()
    CalFile.retrieve("http://[school website]/ical/group/{0}.ics".format(Class), "Data/{0}.ics".format(Class))

    # Update progress bar
    self.Progressbar["value"] += 1

for Study in self.Parameters["Classes"]:
    for Class in Study:
        DownloadFile(Class)

Notes: In this code AllClasses is a list of different classes from which a calendar file has to be downloaded.
The code itself is part of a fairly large class which I didn't include. This is why I am using self.[variablename]

When this code runs the progressbar doesn't load or update, all the files download properly and when they are downloaded the progress bar updates everything at once. My question is: how do I solve this problem in my case?

Answer 1

Try this:

# Update progress bar
self.Progressbar["value"] += 1
self.Progressbar.update_idletasks()

If it does not work then use self.Progressbar.update() instead.

The GUI won't reflect your changes if there is something else to do (like downloading the next file) unless you call update_idletasks() or update() .