Alloy - Attach keyboardToolBar to textfield in the traditional way not work

Add keyboardToolbar does not work whereas setHint works perfectly.

Any idea why?

main.xml

.....
...
..
<Require type="view" src="search_bar" id="req_tf"/>
......
....
..

/*
 * Not functional 
 *
/ 
$.req_tf.getView("field").setKeyboardToolBar([Titanium.UI.createButton({
    title : 'Done',
    style : Titanium.UI.iPhone.SystemButtonStyle.DONE,
}), Titanium.UI.createButton({
    systemButton : Titanium.UI.iPhone.SystemButton.FLEXIBLE_SPACE
}), Titanium.UI.createButton({
    systemButton : Titanium.UI.iPhone.SystemButton.CANCEL
})]);
 
 
/*
 *  Code below works fine
 *
/ 
$.req_tf.getView("field").setHintText("This is a lovely day");