python - 尽管 update_idletasks() ，tkinter 光标直到操作后才发生变化

Question

我正在尝试更改 tkinter 程序中的光标以显示程序正在工作，但光标只会更改为工作光标，直到工作完成后，这是我可以制作代码的压缩方式

警告:为了演示工作原理，当您按转到第一页时，它将计数到 99,999,999

import tkinter as tk                # python 3
from tkinter import font  as tkfont # python 3
#import Tkinter as tk     # python 2
#import tkFont as tkfont  # python 2

class SampleApp(tk.Tk):
    def __init__(self, *args, **kwargs):
        tk.Tk.__init__(self, *args, **kwargs)
        self.title_font = tkfont.Font(family='Helvetica', size=18, weight="bold", slant="italic")

        container = tk.Frame(self)
        container.pack(side="top", fill="both", expand=True)
        container.grid_rowconfigure(0, weight=1)
        container.grid_columnconfigure(0, weight=1)
        self.frames = {}
        for F in (StartPage, PageOne):
            page_name = F.__name__
            frame = F(parent=container, controller=self)
            self.frames[page_name] = frame

            frame.grid(row=0, column=0, sticky="nsew")
        self.show_frame("StartPage")

    def show_frame(self, page_name):
        '''Show a frame for the given page name'''
        frame = self.frames[page_name]
        frame.tkraise()


class StartPage(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        self.controller = controller
        label = tk.Label(self, text="This is the start page", font=controller.title_font)
        label.pack(side="top", fill="x", pady=10)

        button1 = tk.Button(self, text="Go to Page One",
                            command=self.go)
        button1.pack()

    def go(self):
        # do something for like 5 seconds to demonstrate working
        working(True)
        l = [x for x in range(99999999)]
        self.controller.show_frame('PageOne')


class PageOne(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        self.controller = controller
        label = tk.Label(self, text="This is page 1", font=controller.title_font)
        label.pack(side="top", fill="x", pady=10)
        button = tk.Button(self, text="Go to the start page",
                           command=self.back)
        button.pack()

    def back(self):
        working(False)
        self.controller.show_frame('StartPage')


def working(yesorno):
    if yesorno==True:
        app.config(cursor='wait')
    else:
        app.config(cursor='')
    app.update_idletasks()


if __name__ == "__main__":
    app = SampleApp()
    app.mainloop()

编辑:谢谢Switch between two frames in tkinter对于此应用布局示例

Answer 1

这段代码在 Windows 10 和 Python 3 中进行了测试。我发现光标不会改变，直到控制权返回到主循环。这里的代码概述了如何在长时间运行的任务期间一致地显示繁忙的光标。此外，此代码演示了如何从长时间运行的任务中检索数据(例如数据库查询的结果)。

#! python3
'''
Everything you need to run I/O in a separate thread and make the cursor show busy
Summary:
    1. Set up to call the long running task, get data from windows etc.
        1a. Issue a callback to the routine that will process the data
    2. Do the long running task - absolutely no tkinter access, return the data
    3. Get the data from the queue and process away. tkinter as you will
'''

import tkinter as tk
import tkinter.ttk as ttk
from threading import Thread
from threading import Event
import queue


class SimpleWindow(object):
    def __init__(self):

        self._build_widgets()

    def _build_widgets(self):
        # *************************************************************************************************
        # * Build buttons and some entry boxes
        # *************************************************************************************************
        g_col = 0
        g_row = 0
        WaiterFrame = ttk.Frame()
        WaiterFrame.pack( padx=50)

        i = 0
        g_row += 1
        longWaitButton = ttk.Button(WaiterFrame, text='Long Wait',command=self.setup_for_long_running_task)
        longWaitButton.grid(row = g_row, column = i, pady=4, padx=25)
        i += 1
        QuitButton = ttk.Button(WaiterFrame, text='Quit', command=self.quit)
        QuitButton.grid(row = g_row, column = i,pady=4, padx=25)
        i += 1
        self.Parm1Label = ttk.Label(WaiterFrame, text="Parm 1 Data")
        self.Parm1Label.grid(row = g_row-1, column = i, pady=4, padx=2)
        self.Parm1 = ttk.Entry(WaiterFrame)
        self.Parm1.grid(row = g_row, column = i, pady=4, padx=2)

        i += 1
        self.Parm2Label = ttk.Label(WaiterFrame, text="Parm 2 Data")
        self.Parm2Label.grid(row = g_row-1, column = i, pady=4, padx=2)
        self.Parm2 = ttk.Entry(WaiterFrame)
        self.Parm2.grid(row = g_row, column = i, pady=4, padx=2)

        i += 1
        self.Parm3Label = ttk.Label(WaiterFrame, text="Parm 3 Data")
        self.Parm3Label.grid(row = g_row-1, column = i, pady=4, padx=2)
        self.Parm3 = ttk.Entry(WaiterFrame)
        self.Parm3.grid(row = g_row, column = i, pady=4, padx=2)

        i += 1
        self.Parm4Label = ttk.Label(WaiterFrame, text="Parm 4 Data")
        self.Parm4Label.grid(row = g_row-1, column = i, pady=4, padx=2)
        self.Parm4 = ttk.Entry(WaiterFrame)
        self.Parm4.grid(row = g_row, column = i, pady=4, padx=2)

    def quit(self):
        root.destroy()
        root.quit()

    def setup_for_long_running_task(self):
        # ********************************************************************************************************
        # * Do what needs to be done before starting the long running task in a thread
        # ********************************************************************************************************
        Parm1, Parm2, Parm3, Parm4 = self.Get_Parms()

        root.config(cursor="wait")  # Set the cursor to busy

        # ********************************************************************************************************
        # * Set up a queue for thread communication
        # * Invoke the long running task (ie. database calls, etc.) in a separate thread
        # ********************************************************************************************************
        return_que = queue.Queue(1)
        workThread = Thread(target=lambda q, w_self, p_1, p_2, p_3, p_4: \
                            q.put(self.long_running_task(Parm1, Parm2, Parm3, Parm4)),
                            args=(return_que, self, Parm1, Parm2, Parm3, Parm4))
        workThread.start()
        # ********************************************************************************************************
        # * Busy cursor won't appear until this function returns, so schedule a callback to accept the data
        # * from the long running task. Adjust the wait time according to your situation
        # ********************************************************************************************************
        root.after(500,self.use_results_of_long_running_task,workThread,return_que)  # 500ms is half a second

    # ********************************************************************************************************
    # * This is run in a thread so the cursor can be changed to busy. NO tkinter ALLOWED IN THIS FUNCTION
    # ********************************************************************************************************
    def long_running_task(self, p1,p2,p3,p4):

        Event().wait(3.0)  # Simulate long running task

        p1_out = f'New {p1}'
        p2_out = f'New {p2}'
        p3_out = f'New {p3}'
        p4_out = f'New {p4}'

        return [p1_out, p2_out, p3_out, p4_out]

    # ********************************************************************************************************
    # * Waits for the thread to complete, then gets the data out of the queue for the listbox
    # ********************************************************************************************************
    def use_results_of_long_running_task(self, workThread,return_que):
        ThreadRunning = 1
        while ThreadRunning:
            Event().wait(0.1)  # this is set to .1 seconds. Adjust for your process
            ThreadRunning = workThread.is_alive()

        while not return_que.empty():
            return_list = return_que.get()

        self.LoadWindow(return_list)
        root.config(cursor="")  # reset the cursor to normal

    def LoadWindow(self, data_list):

        self.Parm1.delete(0, tk.END)
        self.Parm2.delete(0, tk.END)
        self.Parm3.delete(0, tk.END)
        self.Parm4.delete(0, tk.END)

        i=0; self.Parm1.insert(0,data_list[i])
        i+=1; self.Parm2.insert(0,data_list[i])
        i+=1; self.Parm3.insert(0,data_list[i])
        i+=1; self.Parm4.insert(0,data_list[i])

    # ********************************************************************************************************
    # * The long running task thread can't get to the tkinter self object, so pull these parms
    # * out of the window and into variables in the main process
    # ********************************************************************************************************
    def Get_Parms(self):
        p1 = self.Parm1Label.cget("text")
        p2 = self.Parm2Label.cget("text")
        p3 = self.Parm3Label.cget("text")
        p4 = self.Parm4Label.cget("text")
        return p1,p2,p3,p4

def WaitForBigData():
    global root

    root = tk.Tk()
    root.title("Wait with busy cursor")
    waitWindow = SimpleWindow()
    root.mainloop()

if __name__ == '__main__':

    WaitForBigData()