Actually you added widget in another window and you are passing another window object in index.js file so only use one window.
index.xml
<Alloy>
<Window class="container" id="principal">
<Require type="widget" src="com.appcelerator.drawer" id="drawer" />
</Window>
</Alloy>
index.js
$.drawer.init({
mainWindow : $.principal,
buttons : [{
id : 'One',
title : 'One',
backgroundcolor : "white",
click : function(e) {
alert("One");
}
}],
gutter : 5,
overrideMenu : true
});
$.principal.open();