使用列表框 Tkinter 中的值在按钮按下时调用函数

Question

我想在按钮的命令中使用从列表框中选择的值，这样在按下“开始”按钮之前不会执行任何代码。

到目前为止，我只看到列表框通过绑定到 来执行选择元素的代码。这对我来说似乎很愚蠢，当然程序应该有某种两阶段选择，以确保用户选择他们想要的内容（切线，抱歉）。

到目前为止，我已经尝试使用 .curselection()[0] 和 .get 为当前选择创建一个变量，但我得到了一个索引错误（可能是因为最初没有选择）。然后，如果我设置了初始选择，我无法更改它，它将始终基于该选择执行。

当然，这应该很容易，但我错过了一些东西。

[编辑] 按照建议添加代码转储：

class DataVisualiser:
    def __init__(self, master):
        master.minsize(width=600, height=400)
        frame = Frame(master)
        frame.grid()

        # Histogram Generator
        hist_options = ["Cat vs. Dog", "Cat Breed", "Dog Breed", "Cat Name", "Dog Name", "Cat Location",
                        "Dog Location", "Cat Registration", "Dog Registration"]
        hist_dd = Listbox(master, bg="#cfcfcf", fg="black", font="Helvetica", height=5, selectmode=SINGLE)
        for o in hist_options:
            hist_dd.insert(0, o)
        hist_dd.grid(row=0, column=0)
        hist_dd.selection_set(first=0)
        hist_scroll = Scrollbar(master, orient=VERTICAL)
        hist_dd["yscrollcommand"] = hist_scroll.set
        hist_scroll["command"] = hist_dd.yview
        hist_scroll.grid(row=0, column=1, rowspan=7, sticky=N+S)
        # scrollbar from: https://www.youtube.com/watch?v=xNLdB0jY1Rg
        # HERE: I want to pass the value from the listbox to another function via this button
        hist_gen = Button(master, text="Go!",
                          command=lambda group=hist_dd.get(hist_dd.curselection()[0]): generate_histogram(group))
        # still need to fully implement this
        hist_gen.grid(row=6, column=0, sticky=W+E)    

def generate_histogram(group):
    print(group)
    return None

root = Tk()
dv = DataVisualiser(root)
root.mainloop()

Answer 1

既然你的DataVisualiser是一个类，最好改成类的其他函数方法。您的变量（或其中的一些）也应该成为类实例变量，以避免使用 global 关键字。

我使用 self 关键字 (self.group) 将 group 变量设置为实例变量，并创建了一个方法 select，该方法会在列表框选择更改时更新该变量。还使函数generate_histogram 成为类方法。您可能还需要根据整体程序目标将其他一些变量设为实例变量。

下面更新的代码有 cmets 来解释其他一些更改/添加。您可能需要根据您使用的Python 版本更改导入语句。

from Tkinter import *

class DataVisualiser:
    def __init__(self, master):
        master.minsize(width=600, height=400)
        frame = Frame(master)
        frame.grid()

        # Histogram Generator
        hist_options = ["Cat vs. Dog", "Cat Breed", "Dog Breed", "Cat Name", "Dog Name", "Cat Location",
                        "Dog Location", "Cat Registration", "Dog Registration"]
        hist_dd = Listbox(master, bg="#cfcfcf", fg="black", font="Helvetica", height=5, selectmode=SINGLE)
        for o in hist_options:
            hist_dd.insert(0, o)
        hist_dd.grid(row=0, column=0)
        hist_dd.selection_set(first=0)
        hist_scroll = Scrollbar(master, orient=VERTICAL)
        hist_dd["yscrollcommand"] = hist_scroll.set
        hist_scroll["command"] = hist_dd.yview
        hist_scroll.grid(row=0, column=1, rowspan=7, sticky=N+S)

        # scrollbar from: https://www.youtube.com/watch?v=xNLdB0jY1Rg
        # HERE: I want to pass the value from the listbox to another function via this button
        self.group = hist_dd.get(hist_dd.curselection()[0]) #make group a class variable

        # don't use default keyword parameters i.e, group= .....
        hist_gen = Button(master, text="Go!",
                          command=lambda: self.generate_histogram(self.group))
        # still need to fully implement this
        hist_gen.grid(row=6, column=0, sticky=W+E)  
        hist_dd.bind('<<ListboxSelect>>', self.select) # bind selecction event to listbox


    #method to change the 'group' variable anytime a listbox selection changes
    def select(self, event):
        widget = event.widget
        selection=widget.curselection()
        self.group = widget.get(selection[0])


    #class method
    def generate_histogram(self, group):
        print(group)
        return None

root = Tk()
dv = DataVisualiser(root)
root.mainloop()

Answer 2

为什么不在 listBox 函数中初始化一个全局变量，该函数存储在列表框中选择的值，然后按钮的回调函数可以使用该全局变量？

下面的代码只是说明了您的代码是如何工作的。

def getRuleAfterButtonPress(valueFromListbox):
    for index,rows in excelFile.iterrows():
        if (int(valueFromListbox)==int(rows[columns[0]][5:10])):
            rightSideText2.delete(1.0,END)
            rightSideText2.insert(END,rows[columns[7]])

def onSelectFromListBox(evt):
    # Note here that Tkinter passes an event object to onselect()
    w = evt.widget
    index0 = int(w.curselection()[0])
    global valueFromListbox
    valueFromListbox = w.get(index0)