Trying to refresh a view after changing the user language (I18n, locale)

I'm trying to build a language selector into my rails app. The
selector is defined within the application layout and upon language
selection the current view should be updated to the selected language.
The selected language should then be passed to all subsequent
requests , the url should take the following form: http://localhost:300/fr/producers
where the selected locale is systematically part of the url.

I have a problem with the selector that does not automatically
'refresh' the view to the selected language upon language selection.
Can somebody help me on this one ?

Here is the relevant parts of the code:

#application_controller.rb :
class ApplicationController < ActionController::Base
  protect_from_forgery

  before_filter :set_locale

  def set_locale
    I18n.locale = params[:locale]
  end

  def default_url_options(options={})
   { :locale => I18n.locale }
  end
end

#The layout application.html.erb:

<!DOCTYPE html>
<html>
<head>
  <title>Test</title>
  <%= stylesheet_link_tag :all %>
  <%= javascript_include_tag :defaults %>
  <%= csrf_meta_tag %>
</head>
<body>
  <%= form_tag '', :method => 'GET' do %>
    <%= select_tag :locale, options_for_select(LANGUAGES,
I18n.locale), :onchange => 'this.form.submit();' %>
  <% end %>

<%= yield %>
</body>
</html>

#routes.rb:
  scope "(/:locale)" do
    resources :producers do
      collection do
        get 'update_regions'
      end
  end

#config/application.rb:
  config.i18n.default_locale = :de

set_locale should trigger if params[:locales] exists and but it should refresh if you submit, are you sure is submitting?