如何在函数完成之前让 tk 显示某些内容

Question

我有这段代码，它下载在线列表中指定的文件，并在执行此操作的同时显示一个加载屏幕，其中包含一个标签，告诉您正在下载哪个文件，并且一个不确定的进度条向用户显示正在发生的事情。下载效果很好，但是不行的是tkinter，要等到进程完成才可以，最后只显示“Download Finished”标签。如何让 tkinter 在函数完成之前显示一个窗口？

我已经试过了

• 拆分成多个函数

• 添加sleep 函数以查看是否有帮助

为了显示我所说的内容，我用一些示例替换了我的原始代码。有谁知道如何让 tkinter 更积极地更新（在功能完成之前）？

#Imports
import urllib.request as ur
import os
from tkinter import *
import tkinter.ttk as ttk
import time as T

#Globals
tk = None
where = None
progressbar = None
progresstitle = None
progressinfo = None
transfer = None

#Make sure that the download directory exists
def checkdir(filename):
    directory = os.path.dirname(filename)
    try:
        os.stat(directory)
    except:
        os.mkdir(directory)  

#First part (read q to see why I split up)
def part1():
    #Get Globals
    global tk
    global where
    global progressbar
    global progresstitle
    global progressinfo
    global transfer

    #Create Window
    tk = Tk()
    tk.title("Downloading...")

    #Find out the location of the online files to download by reading the online txt file which contains their locations
    where = str(ur.urlopen("http://example.com/whatfilestodownload.txt").read())
    where = where[2:(len(where)-1)]
    where = where.split(";")
    #Create the progress bar
    progressbar = ttk.Progressbar(tk, orient=HORIZONTAL, length=200, mode='indeterminate')
    progressbar.grid(row = 2, column = 0)
    #Create the labels
    progresstitle = Label(tk, text = "Downloading Files!", font = ("Helvetica", 14))
    progresstitle.grid(row = 0, column = 0)
    progressinfo = Label(tk, text = "Starting Download...", font = ("Helvetica", 10))
    progressinfo.grid(row = 1, column = 0)

    #Engage Part Two
    part2()

#Part Two
def part2():
    #Get Globals
    global tk
    global where
    global progressbar
    global progresstitle
    global progressinfo
    global transfer
    #Repeat as many times as files described in the only file describing .txt
    for x in where
        #The online file contains "onlinelocation:offlinelocation" This splits them up
        x1 = x.split(":")[0]
        x2 = x.split(":")[1]

        #Read the online file and update labels
        transfer = None
        progressinfo.config(text = str("Downloading " + x2 + "..."))
        transfer = str(ur.urlopen("http://example.com/" + x1).read())
        progressinfo.config(text = str("Configuring downloaded file..."))
        transfer = transfer [2:(len(transfer)-1)]

        #Fix python turning "\n" to "\\n" by reversing
        transfer = transfer.split("\\n")
        transtemp = ""
        for x in transfer:
            transtemp = transtemp + "\n" + x
        transfer = transtemp[1:len(transtemp)]
        progressinfo.config(text = str("Installing " + x2 + "..."))
        tw = None
        checkdir(str(os.getcwd()+"/Downladed/"+x2))
        tw = open(str(os.getcwd()+"/Downloaded/"+x2), "w")
        tw.write(transfer)
        tw.close()
        #See if waiting helps
        T.sleep(0.5)
    part3()
def part3():
    #Get Globals
    global tk
    global where
    global progressbar
    global progresstitle
    global progressinfo
    global transfer
    #Final Screen
    progressbar.grid_remove()
    progressinfo.grid_remove()
    progresstitle.config(text="You have downloaded\n the required files!")
    progressbar.stop()

part1()

Answer 1

如果在 part2() 函数中更新每个正在下载的文件末尾的显示就足够了，您可以使用 update_idletasks() 方法，将其替换为 T.sleep()，这将允许 GUI 在回到你的 for 循环的另一个迭代。

参考：http://effbot.org/tkinterbook/widget.htm#Tkinter.Widget.update_idletasks-method

Answer 2

这就是 Tcl 具有异步 I/O 功能的原因。您需要及时处理窗口系统事件，这样您就不能等待完整的文件下载。相反，您需要分段进行。在 Tcl 中，我们将使用 fileevent 命令来设置每次从套接字获得某些输入时调用的过程。剩下的时间我们可以处理其他事件。在 Python 中，执行此操作的常用方法是 Twisted 包。这使您可以使用twisted 注册事件源并使整个应用程序面向事件。您也可以使用线程并在工作线程上进行下载，但这并不能真正帮助您处理进度通知。连接 Tkinter 和 Twisted 有一些特殊处理 - 请参阅 documentation。