Extjs-Ext.fly() null or not an object

hi i have a tabpanel, in which i have two panel but when i try to show a panel using tabpanel.show(). I am getting this message Ext.fly() null or not an object does an开发者_如何学Cy one know what the problem is..please help

Possibly the tabpanel or one of its child elements is not rendered. Set your debugger to break on error and have a poke around.