它的窗口只包含Gtk.TextView,我想在用户输入时处理事件.

这是我的代码：

#!/usr/bin/gjs

var Gtk = imports.gi.Gtk;

function MainWindow () {
    this._init ();
}

MainWindow.prototype = {
    _init: function () {
        this.window = new Gtk.Window ({
            title: "Just Calculator",window_position: Gtk.WindowPosition.CENTER,default_height: 400,default_width: 440,});

        //this.window.show ();
        this.window.connect ("hide",Gtk.main_quit);
        this.window.connect ("delete-event",function () {
            Gtk.main_quit();
            return true;
        });

        this.textBox = new Gtk.TextView();
        this.textBox.connect('key-press-event',this._keyPress);

        var sw = new Gtk.ScrolledWindow ({shadow_type:Gtk.ShadowType.IN});
        sw.add (this.textBox);
        this.window.add(sw);

        this.window.show_all();
    },_keyPress: function(textview,event) {
        print(event,event.type,event.keyval);
        textview.buffer.text = 'ok';
        return true;
    }
}

Gtk.init (null,null);
var window = new MainWindow ();
Gtk.main ();

它通常工作,但我无法读取event.keyval：控制台输出是“未定义”：

[union instance proxy GIName:Gdk.Event jsobj@0x7f99b1027040 native@0x1dfeab0] undefined undefined

有人能告诉我我做错了什么吗？
谢谢！