新选择后将标记保留在下拉菜单 tkinter 中

Question

Is there any way to keep the marker in a tkinter dropdown menu (OptionMenu)? Let's say I have a dropdown menu having 5 entries ("A", "B", "C", "D", "E"). At the beginning "A" is selected. When I click the dropdown menu and change to eg "C" and reopen it the blue marker disappeared. However, I really would like to see in the dropdown list that C was selected (marked in blue). Especially when having a list of more than 10 elements, it is much faster to recognize by eye which value was selected and how to proceed.

Answer 1

You can use add_checkbutton , which adds checkable commands to the menu. I think this is exactly what you need. This means you should use a normal Menu instead of a OptionMenu...

Answer 2

Question : Keep marker in OptionMenu dropdown, after new selection.

You can do this by using menu.postcommand and a StringVar observer.
To set the marker, use .entryconfig(... with the activeforeground/activebackground value.

---

• Tkinter.Menu.config-method - postcommand
• Tkinter.Menu.entryconfig-method
• StringVar.trace

---

import tkinter as tk


class OptionMenu(tk.OptionMenu):
    def __init__(self, parent, *options, **kwargs):
        self.selected = tk.StringVar(parent, '')  # None default value
        super().__init__(parent, self.selected, *options, **kwargs)

        self.options = options
        menu = self['menu']
        menu.configure(activeforeground='white', activebackground='blue',
                       postcommand=self.postcommand)
        self.normal = {'foreground': menu.cget('foreground'),
                       'background': menu.cget('background')}
        self.active = {'foreground': menu.cget('activeforeground'),
                       'background': menu.cget('activebackground')}

        self.selected.trace("w", self.on_selected)
        self.index = 0

    def get(self):
        return self.selected.get()

    def on_selected(self, *_):
        self['menu'].entryconfig(self.index, **self.normal)
        self.index = self.options.index(self.get())

    def postcommand(self):
        self['menu'].activate(self.index)
        self['menu'].entryconfig(self.index, **self.active)

Usage :

class App(tk.Tk):
    def __init__(self):
        super().__init__()

        options = ['   A   ', '   B   ', '   C   ', '   D   ', '   E   ', '   F   ']
        om = OptionMenu(self, *options)
        om.grid()


if __name__ == "__main__":
    App().mainloop()

Tested with Python: 3.5 - 'TclVersion': 8.6 'TkVersion': 8.6