Tkinter中选择Combobox选项时Listbox选中状态被重置的解决方法

问题根源在于Tkinter的Listbox默认开启了exportselection属性（值为True），当Listbox失去焦点（比如点击Combobox）时，系统会清除它的选中状态，保证同一时间只有一个控件的选中内容被系统共享。

只需要在创建Listbox时添加exportselection=False参数，就能阻止选中状态被自动清除：

self.box = tk.Listbox(frame, selectmode=tk.MULTIPLE, height=4, exportselection=False)

修改后的完整代码如下：

import tkinter as tk
from tkinter import ttk

class CheckboxDropdownApp:
    def __init__(self, master):
        self.master = master
        self.master.title('List box with Scrollbar and Dropdown')

        self.create_widgets()

    def create_widgets(self):
        # Create a frame to hold the Listbox, Scrollbar, and Combobox
        frame = tk.Frame(self.master)
        frame.pack()

        # Create a Listbox with a scrollbar，添加exportselection=False
        self.box = tk.Listbox(frame, selectmode=tk.MULTIPLE, height=4, exportselection=False)
        scrollbar = tk.Scrollbar(frame, orient=tk.VERTICAL, command=self.box.yview)

        self.box.config(yscrollcommand=scrollbar.set)
        values = ['Red', 'Green', 'Blue', 'Purple', 'Yellow', 'Orange', 'Black', 'White']
        for val in values:
            # Add padding to each item
            padded_val = f"   {val}   "
            self.box.insert(tk.END, padded_val)

        self.box.pack(side=tk.LEFT, padx=10, pady=10)
        scrollbar.pack(side=tk.RIGHT, fill=tk.Y)

        # Create a Combobox
        self.dropdown_var = tk.StringVar()
        self.dropdown = ttk.Combobox(frame, values=values, textvariable=self.dropdown_var)
        self.dropdown.set(values[0])
        self.dropdown.pack(pady=10)

        # Create buttons
        show_button = tk.Button(self.master, text='Show', width=25, command=self.clicked)
        show_button.pack()

        close_button = tk.Button(self.master, text='Close', width=25, command=self.master.destroy)
        close_button.pack()

    def clicked(self):
        selected = self.box.curselection()  # returns a tuple
        dropdown_value = self.dropdown_var.get()

        if not selected and not dropdown_value:
            print("No item selected.")
        else:
            print("Selected items:")
            for idx in selected:
                print(self.box.get(idx).strip())  # Remove padding when printing
            print(f"Dropdown selected value: {dropdown_value}")

def main():
    root = tk.Tk()
    app = CheckboxDropdownApp(root)
    root.mainloop()

if __name__ == "__main__":
    main()

exportselection=False会禁用控件选中内容的系统级共享，这样Listbox在失去焦点时就能保留自身的选中状态，不会被Combobox的操作重置。

内容的提问来源于stack exchange，提问作者Tester