Python Tkinter after() 只执行一次 [英] Python Tkinter after() Only Executing Once

问题描述

看起来应该如此简单的事情给我带来了很大的问题.我有一个 Tkinter GUI，我正在尝试定期更新.具体来说，我正在从画布上删除项目并替换它们.作为一个例子，尽管我只是想打印一个证明 after 函数正常工作的语句.当我放置一个按钮并单击它时，一切都很好，但我想使用 after() 函数自动完成它.不过，我没有太多运气让它工作.

Something that seems like it should be so simple is giving me quite an issue. I have a Tkinter GUI that I am trying to update at regular intervals. Specifically I am deleting items off a canvas and replacing them. As an example here though I am just trying to print a statement that proves the after function is working correctly. When I place a button and click it, things work great, but I would like to do it automatically using the after() function. I am not having much luck getting it to work though.

class app():
    def __init__(self, frame):
        self.pad = tk.Canvas(frame)
        self.pad.create_window(10, 10, window=tk.Button(self.pad,command=update)
        self.pack(fill="both")

        #More Stuff

        #Neither one worked
        frame.after(1000,update)
        #self.pad.after(1000,update)

    def update(self):
        print "Updating"
        #More Stuff

if __name__=="__main__":
    root = tk.TK()
    app(root)
    root.mainLoop()

当然这不是完整的代码，但希望它有足够的意义来了解我正在尝试做什么.因此，当我单击按钮时，会看到正在更新"字样.但是当我使用 after 函数时，它在开始时出现一次，再也不会出现.我也是 Python 2.4.4 版本，别以为我没有发言权哈哈.感谢您的任何帮助！

Of course this isn't the complete code, but hopefully it makes enough sense to see what I am trying to do. So when I click the button I see the words "Updating" appear. But when I use the after funciton, it appears once at the start and never again. I am also on Python version 2.4.4, don't judge I have no say in it haha. Thanks for any and all help!

推荐答案

在 update 结束时调用 after :

Place a call to after at the end of update:

def __init__(self, frame):       
    self.frame = frame
    ...
    self.frame.after(1000, self.update)

def update(self): 
    ...
    self.frame.after(1000, self.update)

这是after 的工作方式.它只将回调(例如 self.update)排队一次.根据文档:

This is the way after works. It only queues the callback (e.g. self.update) once. Per the docs:

每次调用此方法只调用一次回调.到不断调用回调，需要在里面重新注册回调本身

The callback is only called once for each call to this method. To keep calling the callback, you need to reregister the callback inside itself

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