How to minimize adobe air android app with as3?

I have 2 buttons in my app ( my app published by flash cs6 for android ). one button for exit app and one button for minimize app (send app to background and show homepage).what is code for 2nd button in as3?

b1.addEventListener(MouseEvent.MOUSE_UP,exitapp);
b2.addEventListener(MouseEvent.MOUSE_UP,minimizeapp);
function exitapp(e:MouseEvent)
{
     nativeapplication.nativeapplication.exit();
}
function minimizeapp(e:MouseEvent)
{
     //...what code I should write here?
}