Filter after Custom Field Type in Custom Filter
If you create a new field type, you need to tell Views about it. The hook in question is  https://api.drupal.org/api/views/views.api.php/function/hook_views_data/7

Through entries in this hook you tell views how to build its SQL queries and render the results. Once you have implemented the hook you'll need to clear cache and hopefully you'll see your fields appearing in the list of filters. If the query/render requirements are not addressed by Views' existing handlers, you'll need to write your own. https://api.drupal.org/api/views/views.api.php/group/views_handlers/7