tinyMCE on dynamically generated textarea doesn't get focus with mceFocus -

after clicking on div generating textarea. after loading tinymce on it. works after loading tinymce want set focus on using "mcefocus". isn't working. no focus set regardless browser try.

$.when(             btn.parent().html('<textarea autocomplete="off" name="' + fld + '" id="' + fld + '" readonly></textarea>')         ).done(function() {             tinymce.execcommand('mceaddcontrol', false, fld);             tinymce.execcommand('mcefocus', false, fld);         });