TKinter 8.5 中的布尔变量 [英] Boolean Variable in TKinter 8.5

问题描述

我在 python shell 中做了这个:

from Tkinter import *v = BooleanVar()

但我收到以下错误:

回溯(最近一次调用最后一次):文件<pyshell#52>"，第 1 行，在 <module> 中v = BooleanVar()文件/usr/lib/python2.7/lib-tk/Tkinter.py"，第 320 行，在 __init__ 中Variable.__init__(self, master, value, name)文件/usr/lib/python2.7/lib-tk/Tkinter.py"，第 185 行，在 __init__ 中self._tk = master.tkAttributeError: 'NoneType' 对象没有属性 'tk'>>>

然后在尝试让它发挥作用的同时，我尝试了这个:

v = BooleanVar

这奏效了.

所以我继续做下一个合乎逻辑的事情，检查变量是否已经初始化并得到这个:

<预><代码>>>>v

然后我尝试使用值 True 进行初始化，为此我使用了 set 方法:

v.set(True)

我收到以下错误:

回溯(最近一次调用最后一次):文件<pyshell#63>"，第 1 行，在 <module> 中v.set(真)类型错误:必须使用 BooleanVar 实例作为第一个参数调用未绑定的方法 set()(改为使用 bool 实例)

发生了什么?

请帮我解决这个问题

目标我想将其用作与菜单中的复选按钮相关联的变量

规格 Linux mint 14、python 2.7、Tkinter 8.5

解决方案

简答:首先调用 root = tk.Tk().

<小时>

长答案:引发错误的行，

self._tk = master.tk

失败，因为 master 是 None.但是，请查看此行上方的代码(在 Tkinter.py 中):

class 变量:def __init__(self, master=None, value=None, name=None):如果不是大师:主 = _default_root...self._tk = master.tk

如果您显式地将 master 小部件传递给 BooleanVar(它是 Variable 的子类)，则 master不会是 None.或者，如果 _default_root 不是 None，那么 master 不会是 None.

<小时>

在普通的 Tkinter 应用程序中，您将在制作 BooleanVar 之前制作一个根窗口.在这种情况下，tk.BooleanVar() 不会引发错误.

root = tk.Tk() 将 _default_root 全局变量设置为自身(只要 useTk 参数为 True -- 默认情况下是这样).如果没有使用 tk.BooleanVar(master) 显式设置主控，_default_root 被 BooleanVar 用作小部件的主控.

总而言之，在调用 tk.BooleanVar() 之前，要么调用 root = tk.Tk() 或类似的东西来设置 _default_root>，或者传递一个显式主控件作为第一个参数:tk.BooleanVar(master).

在[1]中:将Tkinter导入为tk在 [2] 中:root = tk.Tk()在 [3] 中:x = tk.BooleanVar()在 [4]: x.set(True)在 [5] 中:x.get()出[5]:1

I did this inside the python shell:

from Tkinter import *

v = BooleanVar()

But I got the following error:

Traceback (most recent call last):
  File "<pyshell#52>", line 1, in <module>
    v = BooleanVar()
  File "/usr/lib/python2.7/lib-tk/Tkinter.py", line 320, in __init__
    Variable.__init__(self, master, value, name)
  File "/usr/lib/python2.7/lib-tk/Tkinter.py", line 185, in __init__
    self._tk = master.tk
AttributeError: 'NoneType' object has no attribute 'tk'
>>> 

And then while just playing around trying to make it work I tried this:

v = BooleanVar

And this worked.

So I went on to do the next logical thing, checking if the variable has been initialised and got this:

>>> v
<class Tkinter.BooleanVar at 0xb6f666bc>

Then I tried to initialise with the value True and for that I used the set method:

v.set(True)

For which I got the following error:

Traceback (most recent call last):
  File "<pyshell#63>", line 1, in <module>
    v.set(True)
TypeError: unbound method set() must be called with BooleanVar instance as first argument (got bool instance instead)

What is going on?

Please help me with this issue

Goal I want to use this as the variable associated with a check button in a menu

specs Linux mint 14, python 2.7, Tkinter 8.5

解决方案

Short answer: Call root = tk.Tk() first.

---

Long answer: The line that is raising the error,

self._tk = master.tk

is failing because master is None. However, look at the code (in Tkinter.py) above this line:

class Variable:
    def __init__(self, master=None, value=None, name=None):

        if not master:
            master = _default_root
        ...
        self._tk = master.tk

If you explicitly pass a master widget to BooleanVar (which is a subclass of Variable) then master would not be None. Or, if _default_root were not None, then master would not be None.

---

In a normal Tkinter application, you will make a root window before making a BooleanVar. In that case, tk.BooleanVar() will not raise an error.

root = tk.Tk() sets the _default_root global variable to itself (as long as the useTk parameter is True -- which it is by default). The _default_root is used by BooleanVar as the widget's master if no master is explicitly set with tk.BooleanVar(master).

So in summary, either call root = tk.Tk() or something similar to set the _default_root before calling tk.BooleanVar(), or pass an explicit master widget as the first argument: tk.BooleanVar(master).

In [1]: import Tkinter as tk

In [2]: root = tk.Tk()

In [3]: x = tk.BooleanVar()

In [4]: x.set(True)

In [5]: x.get()
Out[5]: 1

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