如何在Gjs/Gtk中将按钮添加到主菜单栏

const Gtk = imports.gi.Gtk;

Gtk.init(null);

let window = new Gtk.Window();
window.set_title("菜单栏示例");
window.set_default_size(200, 200);
window.connect("destroy", Gtk.main_quit);

let mainBox = new Gtk.Box({ orientation: Gtk.Orientation.VERTICAL });
window.add(mainBox);

// 创建菜单栏
let menuBar = new Gtk.MenuBar();
mainBox.pack_start(menuBar, false, false, 0);

// 创建菜单按钮
let menuButton = new Gtk.MenuItem({ label: "菜单按钮" });

// 创建菜单
let menu = new Gtk.Menu();
menuButton.set_submenu(menu);

// 创建按钮
let button1 = new Gtk.MenuItem({ label: "按钮1" });
let button2 = new Gtk.MenuItem({ label: "按钮2" });

// 将按钮添加到菜单
menu.append(button1);
menu.append(button2);

// 将菜单按钮添加到菜单栏
menuBar.append(menuButton);

window.show_all();

Gtk.main();