如何在 tkinter 倒数计时器上实现启动、停止和重置功能？

Question

This code runs 25 minute, 5 minute, or 10 minute countdown timer based on which button is chosen. How can I make a running timer pause,resume, and reset? I need help writing callbacks for these three functionalities. They are to be linked to the three buttons up at the top of the window. Here's my code below:

from tkinter import *

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

    def createWidgets(self):
        self.someFrame = Frame(self)
        self.startButton = Button(self.someFrame, text="Start",command=self.startTime)
        self.startButton.pack(side=LEFT)

        self.stopButton = Button(self.someFrame, text="Stop", command=self.stopTime)
        self.stopButton.pack(side=LEFT)

        self.resetButton = Button(self.someFrame, text="Reset", command=self.resetTime)
        self.resetButton.pack(side=LEFT)
        self.someFrame.pack(side=TOP)

        self.labelvariable = StringVar()
        self.labelvariable.set("25:00")

        self.thelabel = Label(self,textvariable = self.labelvariable,font=('Helvetica',50))
        self.thelabel.pack(side=TOP)

        self.firstButton = Button(self,text="pomodoro",command=self.pomodoro)
        self.firstButton.pack(side=LEFT)

        self.secondButton = Button(self,text="short break",command=self.shortBreak)
        self.secondButton.pack(side=LEFT)

        self.thirdButton = Button(self,text="long break",command=self.longBreak)
        self.thirdButton.pack(side=LEFT)

    def pomodoro(self):
        if self._alarm_id is not None:
            self.master.after_cancel(self._alarm_id)
        self.countdown(1500)

    def shortBreak(self):
        if self._alarm_id is not None:
            self.master.after_cancel(self._alarm_id)
        self.countdown(300)

    def longBreak(self):
        if self._alarm_id is not None:
            self.master.after_cancel(self._alarm_id)
        self.countdown(600)


    def startTime(self):
        pass

    def stopTime(self):
        pass

    def resetTime(self):
        pass

    def countdown(self, timeInSeconds):
        mins,secs = divmod(timeInSeconds, 60)
        timeformat = "{0:02d}:{1:02d}".format(mins, secs)
        app.labelvariable.set(timeformat)
        self._alarm_id = self.master.after(1000, self.countdown, timeInSeconds-1)


if __name__ == '__main__':
    root = Tk()
    root.title("Timer")
    app = Application(root)
    root.mainloop()

Answer 1

Your question is still a little vague about precisely what you want to happen when each of the three buttons is clicked, so I had to guess. To support the ability to do these things required adding a couple more instance attributes to keep track of the state of the application—namely self._paused and self._starttime . These can be checked and updated in the various methods as necessary.

from tkinter import *

class Application(Frame):
    def __init__(self,master):
        super(Application,self).__init__(master)
        self.pack()
        self.createWidgets()
        self._alarm_id = None
        self._paused = False
        self._starttime = 25 * 60

    def createWidgets(self):
        self.someFrame = Frame(self)
        self.startButton = Button(self.someFrame, text="Start",command=self.startTime)
        self.startButton.pack(side=LEFT)

        self.stopButton = Button(self.someFrame, text="Stop", command=self.stopTime)
        self.stopButton.pack(side=LEFT)

        self.resetButton = Button(self.someFrame, text="Reset", command=self.resetTime)
        self.resetButton.pack(side=LEFT)
        self.someFrame.pack(side=TOP)

        self.labelvariable = StringVar()
        self.labelvariable.set("25:00")

        self.thelabel = Label(self,textvariable = self.labelvariable,font=('Helvetica',50))
        self.thelabel.pack(side=TOP)

        self.firstButton = Button(self,text="pomodoro",command=self.pomodoro)
        self.firstButton.pack(side=LEFT)

        self.secondButton = Button(self,text="short break",command=self.shortBreak)
        self.secondButton.pack(side=LEFT)

        self.thirdButton = Button(self,text="long break",command=self.longBreak)
        self.thirdButton.pack(side=LEFT)

    def pomodoro(self):
        if self._alarm_id is not None:
            self.master.after_cancel(self._alarm_id)
        self.countdown(1500)

    def shortBreak(self):
        if self._alarm_id is not None:
            self.master.after_cancel(self._alarm_id)
        self._paused = False
        self.countdown(300)

    def longBreak(self):
        if self._alarm_id is not None:
            self.master.after_cancel(self._alarm_id)
        self._paused = False
        self.countdown(600)

    def startTime(self):
        """ Resume """
        self._paused = False
        if self._alarm_id is None:
            self.countdown(self._starttime)

    def stopTime(self):
        """ Pause """
        if self._alarm_id is not None:
            self._paused = True

    def resetTime(self):
        """ Restore to last countdown value. """
        if self._alarm_id is not None:
            self.master.after_cancel(self._alarm_id)
            self._alarm_id = None
            self._paused = False
            self.countdown(self._starttime)
            self._paused = True

    def countdown(self, timeInSeconds, start=True):
        if start:
            self._starttime = timeInSeconds
        if self._paused:
            self._alarm_id = self.master.after(1000, self.countdown, timeInSeconds, False)
        else:
            mins, secs = divmod(timeInSeconds, 60)
            timeformat = "{0:02d}:{1:02d}".format(mins, secs)
            app.labelvariable.set(timeformat)
            self._alarm_id = self.master.after(1000, self.countdown, timeInSeconds-1, False)


if __name__ == '__main__':
    root = Tk()
    root.title("Timer")
    app = Application(root)
    root.mainloop()