如何更新 OptionMenu 的命令 [英] How to update the command of an OptionMenu

问题描述

我正在尝试在实例化后设置或更新 OptionMenu 的命令.

I am trying to set or update the command of an OptionMenu after its instantiation.

widget.configure(command=foo) 语句适用于 Button 和 CheckButton，但不适用于 OptionMenu.

The widget.configure(command=foo) statement works for Button and CheckButton, but not for OptionMenu.

以下代码引发此错误:_tkinter.TclError: unknown option "-command"

from Tkinter import Tk, OptionMenu, StringVar

root = Tk()
var = StringVar()

def foo(val):
    print val, var.get()

widget = OptionMenu(root, var, "one", 'two')
widget.configure(command=foo)
widget.pack()
root.mainloop()

推荐答案

我认为您真正要问的是如何将命令与 Optionmenu 相关联，而不是 update 一个命令(没有命令，所以没有什么要更新的).

I think what you're really asking is how to associate a command to an Optionmenu, rather than update a command (there is no command, so there's nothing to update).

如果您希望每次从 Optionmenu 中选择一个值时都调用一个函数，您可以在相关变量上添加跟踪.无论是通过 Optionmenu 还是任何其他方式，只要该变量发生变化，跟踪就会调用一个函数.

If you want a function to be called every time a value is selected from an Optionmenu, you can add a trace on the related variable. The trace will call a function whenever that variable changes, whether through the Optionmenu or any other means.

例如:

...
var = tk.StringVar()
def foo(*args):
    print "the value changed...", var.get()
var.trace("w", foo)
...

当函数被调用时，它将传递三个参数，在这种情况下你可以安全地忽略它们.

When the function is called it will pass three arguments, which you can safely ignore in this case.

有关变量跟踪的更多信息，请参见 http://effbot.org/tkinterbook/variable.htm

For more information on variable traces see http://effbot.org/tkinterbook/variable.htm

您可能还想考虑切换到 ttk 组合框.它支持绑定到 <<ComboboxSelected>>，这比做一个变量跟踪要稍微简单一些.

You might also want to consider switching to the ttk combobox. It supports binding to <<ComboboxSelected>>, which is every so slightly less clunky than doing a variable trace.

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