iOS keyboard - close issues

My application is in portrait mode. Adobe air 19.x - iOS 9.1 - IPhone 6

You can not close the keyboard manually ... "this.stage.focus = null;" not working.

descr.type = TextFieldType.INPUT ;
descr.restrict = "\u0020-\u007E \\è\\é\\ò\\à\\ù\\ì\\€"; 
descr.maxChars = 120;
descr.addEventListener( FocusEvent.FOCUS_IN, doFocusIn )
descr.addEventListener(KeyboardEvent.KEY_UP, onKeyEvent);
 function onKeyEvent(e:KeyboardEvent):void
{


 if (e.keyCode==13)
 {
  if (stage.focus.name=="descr") 
  {
  trace ("Enter")
  this.stage.focus = null;;
  }

 }
} 
function doFocusIn( event:FocusEvent ):void
{


  trace ("Press") 


}