在我的侧栏中点击下一页后，下拉值不成立

Question

I have drop down in my side bar menu on that menu list I have drop down list.In that list I have Reports main lint in Reports I have sub list Booking.When I select Booking sub list it goes to other page but my drop down sub list close.

Flowing are my code of side bar

<style>
      .nav-link{display:block;padding:.5rem 1rem}
      .nav-link:focus,.nav-link:hover{text-decoration:none}
      .nav-link.disabled{color:#5882FA}
      .nav-icon{text-align:center;width:1.6rem;font-size:1.2rem;margin-right:.2rem}
      .nav-treeview{display:none;list-style:none;padding:0}.nav-sidebar .nav-treeview>.nav-item>.nav-link>.nav-icon{width:1.6rem}

      .mainmenu{
         color: #ffffff !important; background-color: #6D82FB !important;

      }
      .submenu{
         color: #ffffff !important; background-color: #5caaff !important;
      }
      .submenuitem{ 
         color: #ffffff !important; background-color: #9997ff !important;
      }

</style>

<!-- Main Sidebar Container -->
<aside class="main-sidebar sidebar-dark-primary elevation-4">
   <!-- Brand Logo -->
   <a href="<?php echo base_url(); ?>" class="brand-link">
   <img src="<?php echo base_url(); ?>assets/dist/img/barque-logo.png" alt="Barque Logo">
   </a>
   <!-- Sidebar -->
   <div class="sidebar">
      <!-- Sidebar user panel (optional) -->
      <div class="user-panel mt-3 pb-3 mb-3 d-flex">
         <div class="image">
            <a href="<?php echo base_url(); ?>user/UserProfileController/" class="d-block">
               <img src="<?php echo base_url(); echo $this->session->userdata('user_pic_thumb_url'); ?>" class="img-circle elevation-2" alt="User Image">
            </a>
         </div>
         <div class="info">
            <a href="<?php echo base_url(); ?>user/UserProfileController/" class="d-block"><?php echo $this->session->userdata('user_full_name'); ?></a>
         </div>
      </div>
      <!-- Sidebar Menu -->
      <nav class="mt-2">
         <ul class="nav nav-pills nav-sidebar flex-column" data-widget="treeview" role="menu" data-accordion="true">


        <li class="nav-item has-treeview ">
               <a href="#" class="nav-link mainmenu ">
                  <i class="nav-icon fa fa-print"></i>
                  <p>
                     Reports
                     <i class="right fa fa-angle-left"></i>
                  </p>
               </a>
               <ul class="nav nav-treeview nav-item has-treeview">
                   <li class="nav-item">
                     <a href="<?php echo base_url(); ?>reports/BookingController/bookingPage" class="nav-link submenu">
                        <i class="fa fa-file-text nav-icon"></i>
                        <p>Booking
                           <i class="right "></i>
                        </p>
                     </a>
                  </li>
                  <li class="nav-item">
                     <a href="<?php echo base_url(); ?>reports/VehicleLoadedController/vehicleLoadedPage" class="nav-link submenu">
                        <i class="fa fa-file-text nav-icon"></i>
                        <p>Vehicle Loaded
                           <i class="right "></i>
                        </p>
                     </a>
                  </li>
               </ul>
            </li>

         </ul>
      </nav>
      <!-- /.sidebar-menu -->
   </div>
   <!-- /.sidebar -->
</aside>