navigationbar default back button

[nareh tank]

How can I change deafult back button to icon in navigation bar?

[nareh tank]

I got the solution....
set the config of nevigation back button and you can get using this code

viewObject.getNavigationBar().backButton.setConfig({
                        iconMask: true,
                        iconCls: 'action',
                  }); 

and set
defaultBackButtonText:'      ',
otherwise icon is not display properly.
it may help you..