Wpg_docload.download_file to download a zipped file...not working

Question

I am working with APEX 4.1
Within the application being developed, it is a requirement to be able to select multiple rows within an interactive report, then click a button to download these as a ZIP file.
Currently, a field is populated that contains a colon-delimited list of ID values to determine which rows to download, like ":17:127:"
Upon submitting the page files are chosen and zipped through a process, then downloaded through the same process.
Here is the PL/SQL process for zip and download:
declare
  g_zipped_blob blob;
  b_dl_file BLOB;
  v_filename VarChar(1000);
begin
for rec in ( select FILE_ID, FILENAME, FILE_BLOB
from DD_FILES
where instr(:P9_FILE_ID, ':' || FILE_ID || ':') > 0)
LOOP
  zip_blobs.add1file( g_zipped_blob, rec.FILENAME, rec.FILE_BLOB );
end loop;
  zip_blobs.finish_zip( g_zipped_blob );
  select sysdate into v_filename from dual;
  owa_util.mime_header( 'application/octet', false );
  htp.p('Content-length: ' || dbms_lob.getlength(g_zipped_blob));
  htp.p('Content-Disposition:  attachment; filename="'|| v_filename ||'.zip"');          
  owa_util.http_header_close;
  wpg_docload.download_file(g_zipped_blob);
--dbms_lob.freetemporary( g_zipped_blob);
end;add1file and finish_zip are stored procedures.
Currently upon pressing the button, nothing happens(but the page is submitted, nothing seems to happen), although when testing the process, it returns what appears to be a text version of the BLOB (within the SQL commands section of the SQL workshop).
Any reasons why this would be happening?
Already posted this in the PL/SQL section but it seems to have been ignored.

Answer 1

Hi,
Rather than submitting the page I would try opening a new page (for example, by calling popUpNamed) passing the ids as a parameter to this page. Then have your download process as a before header process on this page.
Use apex_application.g_unrecoverable_error := TRUE; at the end of your code to ensure that none of the page processing for this page is actually run.
Rod West