Joomla: how to display sub-menu items - joomla

Question

I created a website using Joomla! 3.4.1. It has some categories and the main menu looks like this:
Home
Main Category
Category 1
Category 1.1
Category 1.1.1
Category 1.1.2
Category 1.1.3
Category 1.2
Category 1.3
Category 2
Category 2.1
Category 2.2
I decided (I'm not sure if it was the best decision) to create the complete website structure in the main menu.
Now, in the "Category 1" page, I would like to have a menu showing some selected sub-menu items, for example:
Category 1 Menu:
Category 1.1
Category 1.3
In order to achieve this, I decided to create a new menu called "Category 1 Menu" with menu item aliases (to avoid creating new URLs).
Until now everything was ok, the problem is now I want to display Category 1.1 sub-items, but I just want to display the children of Category 1.1 when Category 1.1 is selected. Something like this:
Category 1
Category 1.1
Category 1.3
And if I click on "Category 1.1" its items should expand like this:
Category 1
Category 1.1
Category 1.1.1
Category 1.1.2
Category 1.1.3
Category 1.3
Remember, all these items are menu item aliases.
I know how to do it without usign menu item aliases but in this case, I think that I need to use menu item aliases, otherwise I won't have a complete "tree" structure in the breadcrumbs.
What can I do?
Thanks in advance!

Answer 1

if you don't wanna use aliases you can easily create a module or search for one in JED. Basically code for sub menu is like this:
$menu = JFactory::getApplication()->getMenu();
$active = $menu->getActive();
$childs = $menu->getItems('parent_id', $active->id);
//now if childs are empty yoy don't have a submenu
if( !empty($childs) )
{
//show menu using foreach $childs as $child and creating friendly url using JRoute
}