Hi Manjunath,
I think this might be related to the ADT installation you are using. You might ask for more information on how to solve the issue with the ADT colleagues in the community: ABAP in Eclipse.
Additionally, can you try to create a small report, something like:
data lt_res type standard table of zext_an_view.
select * from zext_an_view into table lt_res.
cl_demo_output=>display_data( lt_res ).
If that works, everything is fine with the external view and the issue is rather related to your IDE.
BTW, are you running a recent version of ADT (see SAP Development Tools for Eclipse for an Eclipse installation + ADT plugins).
Cheers,
Jasmin