addEventListener and tabs

when I switching tabs for some reason addEventListener stops working and in a illustrator not working at all.

var dialog = new Window("dialog");

var tpanel1 = dialog.add("tabbedpanel", undefined, undefined, { name: "tpanel1" });
var tab1 = tpanel1.add("tab", undefined, undefined, { name: "tab1" });
tab1.text = "Tab1";

var button1 = tab1.add("button", undefined, undefined, { name: "button1" });
button1.text = "Button_01";

var tab2 = tpanel1.add("tab", undefined, undefined, { name: "tab2" });
tab2.text = "Tab2";

var button4 = tab2.add("button", undefined, undefined, { name: "button4" });
button4.text = "Button_03";

tab1.addEventListener('keydown', alertKey);

function alertKey() {
    var myKeyState = ScriptUI.environment.keyboardState;
    var pressedString = myKeyState.keyName;

    if (myKeyState.keyName) {
        alert("You pressed " + pressedString);
    }
}
dialog.show();