如何使 GTK 菜单项可点击？

Question

我正在尝试将菜单模型附加到菜单按钮。

import gi
gi.require_version('Gtk', '4.0')
from gi.repository import Gio, Gtk


def on_activate(app):
    win = Gtk.ApplicationWindow(application = app)

    actions = Gio.Menu()
    btn = Gtk.MenuButton(label = 'Menu')
    Gio.SimpleAction.new('whatever', None).connect('activate', print)
    actions.append('Do whatever', 'whatever')
    btn.set_menu_model(actions)

    win.set_child(btn)
    win.present()


app = Gtk.Application(application_id = 'org.gtk.Example')
app.connect('activate', on_activate)
app.run(None)

无论我做什么，菜单中的项目都无法点击。