Python - 为倒数计时器创建一个取消按钮

Posted 2021-05-04

此代码是模拟智能烤面包机的程序的开始。我正在为我的倒数计时器做一个取消按钮。计时器工作正常，但按下取消按钮时会显示消息“计时器已完成”，但计时器仍在继续。有没有办法可以做到这一点？

from tkinter import *
import time

class Window(Frame): #creating window
def __init__(self, master = None): #defining master window
    Frame.__init__(self, master)
    self.master = master
    self.init_window()

def init_window(self):
    self.master.title("GUI")
    self.pack(fill=BOTH, expand=1) #allowing size of window to be changed during running of program

    #using a slider instead of a dial as no dial in tkinter
    timerinputDial = Scale(self, from_=0, to=6, tickinterval=1, showvalue=0) 
    timerinputDial.place(x=200, y=20)

#Timer

    def count_down():
        for t in range(((timerinputDial.get())*60), -1, -1): #starts with the value of the input dial
            # format as 2 digit integers, fills with zero to the left
            # divmod() gives minutes, seconds
            sf = "{:02d}:{:02d}".format(*divmod(t, 60))
            #print(sf)
            time_str.set(sf)
            root.update()
            # delay one second
            time.sleep(1)
        if t == 0:
            time_str.set(timer_done) #telling user timer is finished
            timerinputDial.set(0) #setting dial back to 0
            return

    def cancel():
        time_str.set(timer_done) #telling user timer is finished
        timerinputDial.set(0) #setting dial back to 0
        return

    time_str = StringVar()
    timer_done = "Timer done"      

    # creating the time display label, giving it a large font
    # labelling auto-adjusts to the font
    label_font = ('helvetica', 40)
    Label(root, textvariable=time_str, font=label_font, bg='white', 
             fg='blue', relief='raised', bd=3).pack(fill='x', padx=5, pady=5)

    # creating start and stop buttons
    # pack() positions the buttons below the label
    startButton = Button(root, text='Start', command=count_down).pack()
    # stop simply exits root window
    cancelButton = Button(root, text='Cancel', command=cancel).pack()

root = Tk()
root.geometry("400x300")

app = Window(root)

root.mainloop()

答案

我刚才做了一个简单的启动/停止计时器。它只是测试一个实例变量来启动和停止。请注意，您应该使用after()而不是time.sleep()来避免循环停止更新其他所有内容。

from tkinter import *

class TimerTest():
    def __init__(self, root):
        self.root=root

        self.is_running=False
        self.count=IntVar()
        self.max_seconds=60  ## quit after this amount of time
        Label(root, textvariable=self.count,
              font=('DejaVuSansMono', 12, "bold"),
              bg="lightyellow").grid(row=1, column=0,
              columnspan=2, sticky="ew")

        Button(root, text="Start", fg="blue", width=15,
                            command=self.startit).grid(row=10,
                            column=0, sticky="nsew")
        Button(root, text="Stop", fg="red", width=15,
                            command=self.stopit).grid(row=10,
                            column=1, sticky="nsew")
        Button(self.root, text="Quit", bg="orange",
                            command=self.root.quit).grid(row=11,
                            column=0, columnspan=2, sticky="nsew")

    def startit(self):
        if not self.is_running:  ## avoid 2 button pushes
            self.is_running=True
            self.increment_counter()

    def increment_counter(self):
        if self.is_running:  ## stopit not called
             c=self.count.get() +1
             self.count.set(c)
             if c < self.max_seconds:
                 self.root.after(1000, self.increment_counter)  ## every second
             else:
                 self.is_running=False
                 Label(root, text="Time Is Up",
                       font=('DejaVuSansMono', 14, "bold"),
                       bg="red").grid(row=5, column=0,
                       columnspan=2, sticky="ew")

    def stopit(self):
        self.is_running = False

root = Tk()
TT=TimerTest(root)
root.mainloop()