tkinter组合框在按箭头键时选择下一个值而不是显示整个列表

Question

我的python应用程序中有几个tkinter组合框，其默认的tkinter行为是'向上'箭头不做任何事情，'向下'箭头显示整个值列表，然后可以使用箭头键反转。
但是，我想在不弹出列表的情况下用箭头键"滚动"组合框(即向下箭头直接切换到下一个元素，向上箭头直接切换到上一个元素)。

组合框MWE:

import tkinter as tk
import tkinter.ttk as ttk
app = tk.Tk()
combo = ttk.Combobox(app, values = [f"item {i}" for i in range(20)])
combo.grid()

(如何)我可以实现这个期望的行为?我是否必须抓住关键事件，或者我是否错过了某些设定?

Answer 1

这是一个解决方案，应该同时适用于Up和Down

import tkinter as tk
import tkinter.ttk as ttk

def select_next(event):
selection = combo.current()  # get the current selection
last = len(combo['values']) - 1  # index of last item
key = event.keysym  # get the key that was pressed
if key == 'Up':
try:
combo.current(selection - 1)  # set the combobox to the previous item
except tk.TclError:  # end of list reached
combo.current(last)  # wrap around to last item
elif key == 'Down':
try:  
combo.current(selection + 1)  # set the combobox to the next item
except tk.TclError:  # end of list reached
combo.current(0)   # wrap around to first item
return 'break'  # tell tk to dispose of this event and don't show the menu!

app = tk.Tk()
combo = ttk.Combobox(app, values = [f"item {i}" for i in range(20)])
combo.grid()
combo.current(0)  # select the first item by default
combo.bind('<Up>', select_next)  # up arrow
combo.bind('<Down>', select_next)  # down arrow