为 ttk Combobox 设置默认值 [英] Set a default value for a ttk Combobox
问题描述
我在 Arch Linux x86_64 中使用 Python 3.2.1.这个真的让我发疯:我只想在我网格后立即为 ttk.Combobox
设置一个默认的预选值.这是我的代码:
I'm using Python 3.2.1 in Arch Linux x86_64.
This one is really driving me crazy: I just want to have a default, preselected value for a ttk.Combobox
as soon as I grid it. This is my code:
from tkinter import Tk, StringVar, ttk
root = Tk()
def combo(parent):
value = StringVar()
box = ttk.Combobox(parent, textvariable=value, state='readonly')
box['values'] = ('A', 'B', 'C')
box.current(0)
box.grid(column=0, row=0)
combo(root)
root.mainloop()
绘制一个空的Combobox
.有趣的是,如果我不使用函数,它就可以完美运行:
Which draws an empty Combobox
. What's funny is that if I don't use a function it works perfectly:
from tkinter import Tk, StringVar, ttk
root = Tk()
value = StringVar()
box = ttk.Combobox(root, textvariable=value, state='readonly')
box['values'] = ('A', 'B', 'C')
box.current(0)
box.grid(column=0, row=0)
root.mainloop()
当然,在实际程序中我必须使用函数,所以我需要另一种解决方案.
Of course, in the real program I have to use a function, so I need another solution.
推荐答案
问题是 StringVar 的实例正在被垃圾收集.这是因为由于您编写代码的方式,它是一个局部变量.
The problem is that the instance of StringVar is getting garbage-collected. This is because it's a local variable due to how you wrote your code.
一种解决方案是使用一个类,以便您的 StringVar 保持不变:
One solution is to use a class so that your StringVar persists:
from tkinter import Tk, StringVar, ttk
class Application:
def __init__(self, parent):
self.parent = parent
self.combo()
def combo(self):
self.box_value = StringVar()
self.box = ttk.Combobox(self.parent, textvariable=self.box_value,
state='readonly')
self.box['values'] = ('A', 'B', 'C')
self.box.current(0)
self.box.grid(column=0, row=0)
if __name__ == '__main__':
root = Tk()
app = Application(root)
root.mainloop()
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