setFocus doesn't work.

Hello, everyone!

<?xml version="1.0" encoding="utf-8"?>
<mx:Canvas
xmlns:mx=" http://www.adobe.com/2006/mxml"
xmlns:ns1="com.something.*"
creationComplete="init();">

<mx:HBox>
<ns1:MyButton label="ok" click="ok_()" id="OKBtn"/>
<ns1:MyButton label="cancel"click="cancel_()" id="CANCELBtn"/>
</mx:HBox>
<!-- something else -->

<mx:Script>
<![CDATA[

// import statements

public function init():void
{
focusManager.activate(); // Doesn't work;
this.OKBtn.setFocus(); // Doesn't work;
}

]]>
</mx:Script>
</mx:Canvas>

// MyButton Class
public class MyButton extends Button
{
public function MyButton()
{
super();
}
}

Anything else I can try?