Problem
You need to display a splash screen when uploading files to a Ruby on Rails application.

Solution
My model:

class Number < ActiveRecord::Base
  file_column :intro
  file_column :vmail
end

The steps I have followed.

1. Install redbox plugin from project path run:

   ./script/plugin install svn://rubyforge.org/var/svn/ambroseplugins/redbox

2. If files redbox.js, redbox.css and redbox_spinner.gif haven’t been copied over to the public folders copy them over manually or go to vendor/plugins/redbox and run:

   rake update_scripts

3. Find an animated gif for the progress indicator to be used (ie pleasewait.gif) and copy it over to public/images.
4. In order to be able to use the progress indicator in different parts of the application, add the following to the app/views/layouts/ :

   application.rhtml
                <%= stylesheet_link_tag 'redbox' %>
               <%= javascript_include_tag 'redbox' %>

   near the place where <= javascript_include_tag :default > is located.
   Also at the bottom of the page create the content of the redbox:

   <p id="redbox" style="display: none"> </p>
   
   <p style="color: blue"> Please wait ....
   
   Uploading files
   
   <img src="/images/pleasewait.gif" width="200" />
   

5. Copy _update_form.rhtml, update_form.rhtml and update.rjs from vendor/plugins/active_scaffold_upload/frontends/default/views/ to the app/views/numbers (model you want to use).
6. To display the redbox in the numbers/_update_form.rhtml add the following in the submit_tag:

    , :onClick => "return RedBox.showInline('redbox') " %>

7. To close the redbox after the uploading was successful, add the following in numbers/update.rjs as the first line inside controller.send :successful? clause:

   page.RedBox.close()