python - TKinter 选项菜单 : How to get the selected choice?

Question

我是 Python 和 Tkinter 的新手，但我必须创建一个需要使用下拉菜单的简单表单。 我试图做这样的事情:

#!/usr/bin python
import sys

from Tkinter import *

# My frame for form
class simpleform_ap(Tk):

    def __init__(self,parent):
        Tk.__init__(self,parent)
        self.parent = parent
        self.initialize()

    def initialize(self):
        self.grid()
        # Dropdown Menu
        optionList = ["Yes","No"]
        self.dropVar=StringVar()
        self.dropVar.set("Yes") # default choice
        self.dropMenu1 = OptionMenu(self, self.dropVar, *optionList)
        self.dropMenu1.grid(column=1,row=4)
        print self.dropVar.get()

def create_form(argv):
    form = simpleform_ap(None)
    form.title('My form')
    form.mainloop()

if __name__ == "__main__":
  create_form(sys.argv)

但是，我打印出来的始终是默认值，而我从未获得从下拉列表中选择的值。

我尝试使用 StingVar 的 .trace 方法来做这样的事情:

#!/usr/bin python
import sys
from Tkinter import *

# My frame for form
class simpleform_ap(Tk):

    def __init__(self,parent):
        Tk.__init__(self,parent)
        self.parent = parent
        self.initialize()

    def initialize(self):
        self.grid()
        # Dropdown Menu
        optionList = ["Yes","No"]
        self.dropVar=StringVar()
        self.dropVar.set("Yes") # default choice
        self.dropMenu1 = OptionMenu(self, self.dropVar, *optionList)
        self.dropMenu1.grid(column=1,row=4)
        self.dropVar.trace("w",self.get_selection)
        print self.dropVar.get()


    def get_selection(self):
        print "Selected: "+ self.dropVar.get()

def create_form(argv):
    form = simpleform_ap(None)
    form.title('My form')
    form.mainloop()

if __name__ == "__main__":
    create_form(sys.argv)

但是我得到了以下错误:

Exception in Tkinter callback Traceback (most recent call last):
File "/usr/lib64/python2.6/lib-tk/Tkinter.py", line 1410, in __call__
    return self.func(*args) TypeError: get_selection() takes exactly 1 argument (4 given)

我做错了什么？

请注意，我不希望使用任何按钮来确认下拉菜单中的选择。

你能给点建议吗？

Answer 1

OptionMenu 有一个内置的 command 选项，它将 menu 的当前状态提供给一个函数。看这个:

#!/usr/bin python
import sys
from Tkinter import *

# My frame for form
class simpleform_ap(Tk):

    def __init__(self,parent):
        Tk.__init__(self,parent)
        self.parent = parent
        self.initialize()
        self.grid()

    def initialize(self):
        # Dropdown Menu
        optionList = ["Yes","No"]
        self.dropVar=StringVar()
        self.dropVar.set("Yes") # default choice
        self.dropMenu1 = OptionMenu(self, self.dropVar, *optionList,
                                    command=self.func)
        self.dropMenu1.grid(column=1,row=4)

    def func(self,value):
        print value


def create_form(argv):
    form = simpleform_ap(None)
    form.title('My form')
    form.mainloop()

if __name__ == "__main__":
    create_form(sys.argv)

这应该如您所愿。