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python - 有哪些技术可以允许 tkinter 程序中的多个线程？

问题描述

我发现了这个简单的 Hello World tkinter 程序：

import tkinter as tk

class Application(tk.Frame):
    def __init__(self, master=None):
        super().__init__(master)
        self.master = master
        self.pack()
        self.create_widgets()

    def create_widgets(self):
        self.hi_there = tk.Button(self)
        self.hi_there["text"] = "Hello World\n(click me)"
        self.hi_there["command"] = self.say_hi
        self.hi_there.pack(side="top")

        self.quit = tk.Button(self, text="QUIT", fg="red",
                              command=self.master.destroy)
        self.quit.pack(side="bottom")

    def say_hi(self):
        print("hi there, everyone!")
        self.hi_there["text"] = "Hello World\n(click me again)"

root = tk.Tk()
app = Application(master=root)
app.mainloop()

如果我想让该say_hi()方法执行长时间运行的任务并偶尔更新 GUI，该怎么办？

如果我试试这个：

    def say_hi(self):
        print("hi there, everyone!")
        self.hi_there["text"] = "Hello World\n(wait...)"

        sleep(2)  # pretend to do something long-running

        self.hi_there["text"] = "Hello World\n(click me again)"

然后 GUI 在睡眠期间锁定，我从来没有看到按钮变为：Hello World\n(wait...)

标签： pythonmultithreadingtkinter

解决方案

一种可能的解决方案是下面的修改Application类，它使用queue一个新方法poll()作为消息泵来操作Thread希望运行的代码项。

from time import sleep
from queue import Queue
from threading import Thread

class Application(tk.Frame):
    def __init__(self, master=None):
        super().__init__(master)
        self.master = master
        self.pack()
        self.create_widgets()
        self.queue = Queue()
        self.poll()        

    def create_widgets(self):
        self.hi_there = tk.Button(self)
        self.hi_there["text"] = "Hello World\n(click me)"
        self.hi_there["command"] = self.start_hi
        self.hi_there.pack(side="top")

        self.quit = tk.Button(self, text="QUIT", fg="red",
                              command=self.master.destroy)
        self.quit.pack(side="bottom")

    def say_hi(self):
        def do_wait():
            self.hi_there["text"] = "Hello World\n(wait...)"
        def do_again():
            self.hi_there["text"] = "Hello World\n(click me again)"

        print("hi there, everyone!")
        self.queue.put(do_wait)
        sleep(2)  # pretend to do something long-running
        self.queue.put(do_again)

    def start_hi(self):
        thread = Thread(target = self.say_hi)
        thread.start()

    def poll(self):
        if not self.queue.empty():
            item = self.queue.get()
            item()
        self.master.after(100, self.poll)

如果您使用该版本的类，那么您会注意到按钮上的版本和文本按预期hi_there Button更改。wait...

注意事项：此代码还允许您创建大量Thread实例，但该poll()方法仅每 100 毫秒轮询一次

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