从其ID获取菜单项标题

I need to get the title of my top-level navigation. I already know the ID of the top-level menu-item but i need to get its title. How can one do that?

I currently have menu like this:

• Level1
  • Level2 #1
  • Level2 #2
  • Level2 #3

If im on any of the level 2 pages i have the Level 1 menu-item ID. I need to get the title in the current theme-location instance.

   <?php if(getTopSelectedMenu('primary')):
            $topParent = intval(getTopSelectedMenu('primary'));
            $topParentTitle = "";
    ?>
        <div class="sidebar-menu-headline"><?=$topParentTitle?><i class="fa fa-arrow-down" aria-hidden="true"></i></div>
    <?php

        $args = array(
            'menu' => '',
            'menu_class' => 'sidebar-menu',
            'container' => 'ul',
            'theme_location' => 'primary',
            'level' => 2,
            'child_of' => $topParent,
            'echo' => FALSE,
            'fallback_cb' => '__return_false'
        );
        $submenu = wp_nav_menu( $args );

        if ( ! empty ($submenu) )echo $submenu;

    ?>

use the below function to get menu title by passing menu id.

Function: wp_get_nav_menu_object($menu) // $menu can be 'id','name' or 'slug'
Returns : Object (
       term_id => 4
       name => My Menu Name
       slug => my-menu-name
       term_group => 0
       term_taxonomy_id => 4
       taxonomy => nav_menu
       description => 
       parent => 0
       count => 6
   )

// in your case.
$menu = wp_get_nav_menu_object($topParent );
$menu_title = $menu->name;

You can find more information here. https://codex.wordpress.org/Function_Reference/wp_get_nav_menu_object

To get the Menu title, Use the below code

if(getTopSelectedMenu('primary')){
    $topParentId = intval(getTopSelectedMenu('primary'));
    $menuLocations = get_nav_menu_locations(); // Get our nav locations (set in our theme, usually functions.php)
                                           // This returns an array of menu locations ([LOCATION_NAME] = MENU_ID);

    $menu =  wp_get_nav_menu_object($menuLocations['primary']) ; // Get the *primary* menu object

    $primaryNav = wp_get_nav_menu_items($menu->term_id); // Get the array of wp objects, the nav items for our queried location.

    foreach ( $primaryNav as $navItem ) {
        if ($navItem->ID == $topParentId ) {
            $topParentTitle = $navItem->title;
        }
    }
}
<div class="sidebar-menu-headline"><?=$topParentTitle?><i class="fa fa-arrow-down" aria-hidden="true"></i></div>