How do I stop tkinter after function?

问题:

I'm having a problem stopping the 'feed'; the cancel argument doesn't seem to have any impact on the after method. Although "feed stopped" is printed to the console.

I'm attempting to have one button that will start the feed and another that will stop the feed.

from Tkinter import Tk, Button import random      def goodbye_world():         print "Stopping Feed"         button.configure(text = "Start Feed", command=hello_world)         print_sleep(True)      def hello_world():         print "Starting Feed"         button.configure(text = "Stop Feed", command=goodbye_world)         print_sleep()      def print_sleep(cancel=False):         if cancel==False:             foo = random.randint(4000,7500)             print "Sleeping", foo             root.after(foo,print_sleep)         else:             print "Feed Stopped"       root = Tk()     button = Button(root, text="Start Feed", command=hello_world)      button.pack()       root.mainloop() 

With the output:

Starting Feed Sleeping 4195 Sleeping 4634 Sleeping 6591 Sleeping 7074 Stopping Feed Sleeping 4908 Feed Stopped Sleeping 6892 Sleeping 5605 

回答1:

The problem is that, even though you're calling print_sleep with True to stop the cycle, there's already a pending job waiting to fire. Pressing the stop button won't cause a new job to fire but the old job is still there, and when it calls itself, it passes in False which causes the loop to continue.

You need to cancel the pending job so that it doesn't run. For example:

def cancel():     if self._job is not None:         root.after_cancel(self._job)         self._job = None  def goodbye_world():     print "Stopping Feed"     cancel()     button.configure(text = "Start Feed", command=hello_world)  def hello_world():     print "Starting Feed"     button.configure(text = "Stop Feed", command=goodbye_world)     print_sleep()  def print_sleep():     foo = random.randint(4000,7500)     print "Sleeping", foo     self._job = root.after(foo,print_sleep) 

Note: make sure you initialize self._job somewhere, such as in the constructor of your application object.

回答2:

When you call root.after(...), it will return an identifier. You should keep track of that identifier (e.g., store it in an instance variable), and then you can later call root.after_cancel(after_id) to cancel it.

文章来源: How do I stop tkinter after function?