在标签Python3 Tkinter的显示列表框项目时，点击

Question

我有这个列表框作为类的一部分：

def myListbox(self): 
selection = Label(self, text="Please select Country").grid(row=0,column=0) 

countries = Listbox(self, width = 20, height = 75) 
countries.grid(row=0, column=1) 

# I have a function that populates the country names from 
# a text file and displays the names in the Listbox. 
# I want to be able to select a country from the Listbox 
# and have it displayed in a Label 

country_display = Label(self, text = "").grid(row = 0, column = 9) 
# this is where I'm not sure what code to use. 
# my code is 
countries.bind("<<ListboxSelect>>",country_display) 

目前什么都不显示。我在这里错过了什么？ 谢谢

Answer 1

首先，当您在窗口小部件上执行方法grid时，它将返回None。这意味着您的变量现在保存值None，而不是对小部件的引用。 其次，方法bind将函数绑定到事件。此功能尚未被调用。但是，在您的bind中，您尝试将Label（不是函数）分配给该事件;这根本不可能。 在下面的解决方案中，将为该事件分配一个函数，该函数将检索国家并设置标签。

from tkinter import * 

countries_list = ["Netherlands", 
        "America", 
        "Sweden", 
        "England"] 

class MyClass(Tk): 
    def myListbox(self): 

     # better to structure it this way. The method grid simply returns None 
     # which meant that the variable hold None 
     # Now, the variable selection holds the widget 
     selection = Label(self, text="Please select Country") 
     selection.grid(row=0,column=0) 

     countries = Listbox(self, width = 20, height = len(countries_list)) 
     countries.grid(row=0, column=1) 
     for country in countries_list: 
      countries.insert(END, country) 

     country_display = Label(self, text = country, width = 15) 
     country_display.grid(row = 0, column = 9) 

     def get_country(*x): 
      # gets which country is selected, and changes 
      # the label accordingly 
      country = countries_list[countries.curselection()[0]] 
      country_display.config(text = country) 
     countries.bind("<<ListboxSelect>>", get_country) 

app = MyClass() 
app.myListbox() 

编辑：获取更多信息Listbox看到http://effbot.org/tkinterbook/listbox.htm （虽然我的感觉，你可能想使用一个Combobox，如http://www.tkdocs.com/tutorial/widgets.html描述？）