无法访问代码点火器视图中的会话数据

我在登录到仪表板后将用户重定向，并且在仪表板标题上，我想显示我存储在会话中的用户名。但是在header中，它会给我提示

Undefined index userData

我已经在应用中设置了模板结构。

:

    <?php
   class Admin extends CI_Controller {
    private $template;
    private $header;
    private $footer;
    private $sidebar;
    private $content;
    public $userData;
    function __construct() {

        parent::__construct(); //call to parent constructor
        $this->data = "";
        $this->header = $this->load->view('admin/header', $this->userData, TRUE);
        $this->template = $this->load->view('admin/template', $this->userData, TRUE);
        $this->footer = $this->load->view('admin/footer', $this->userData, TRUE);
        $this->load->helper('url');
        // $this->loginModel    =   $this->load->model('admin/loginModel');
        session_start();
    }
    /**
     * will show the dashborad
     * index function default function of Admin Controller
     */
    public function index() {
        if ($this->session->userdata('id')) {
            $this->userData = $this->session->userdata;
            $data['userData']   = $this->userData;;
            $data['header'] = $this->header;
            $data['footer'] = $this->footer;
            $data['content'] = $this->load->view('admin/content', $data, TRUE);
            $data['sidebar'] = $this->load->view('admin/sidebar', $data, TRUE);
            $this->load->view('admin/template', $data);
        } else {
            $this->login();
        }
    }
    /**
     * This is the login function of a controller 
     */
    public function login() {

        $data = '';
        if (isset($_POST['submit'])) {
            $username = '';
            $password = '';
            $errors = '';
            $username = mysql_real_escape_string($this->input->post('username'));
            $password = $this->input->post('password');
            if ($username == '') {
                //echo 'dasd';
                $data['username_error'] = 'Username is Required';
            }
            if ($password == '') {
                //echo 'dasd';
                $data['password_error'] = 'Password is Required';
            }
            if ($username == '' && $password == '') {
                //echo 'dasd';
                $data['password_error'] = '';
                $data['username_error'] = '';
                $data['general_error'] = 'Please enter Username and Password to proceed';
            }
            if ($username != '' && $password != '') {
                //varify username password
                $hpassword = $password;
                $this->load->model('admin/loginModel');
                $row = $this->loginModel->verifyUser($username, $password);
                echo "<pre>";
                print_r($row);
                if (!empty($row)) {
                    $adminSessionData = '';
                    foreach($row as $adminData) {
                        $adminSessionData['id'] =   $adminData['pk_admin_id'];
                        $adminSessionData['username'] =   $adminData['admin_username'];
                        $adminSessionData['email'] =   $adminData['admin_email'];
                        $adminSessionData['status'] =   $adminData['admin_status'];
                    }
                    //saving data in session
                    $this->session->set_userdata($adminSessionData);
                    redirect(base_url('admin'));
                } else {
                    $data['general_error'] = 'Invalid Credentials';
                }
            }
        }
        $data['title'] = "Admin Panel Login";
        $this->load->view('admin/login', $data);
    }
    /**
     * will destroy session n logout user
     *
     */
    function logout() {
        $userSessionData = array(
            'user_id' => '',
            'username' => '',
            'email' => ''
        );
        $this->session->unset_userdata($userSessionData);
        $this->session->sess_destroy();
        session_destroy();
        redirect(base_url('admin/login'));
        exit;
    }
}
?>

header。php :

<div class="btn-group user-menu">
                <button type="button" class="btn btn-sm dropdown-toggle" data-toggle="dropdown"> <span class="glyphicons glyphicons-user"></span> <b><?php echo $userData['userData']['username']?></b> </button>
                <button type="button" class="btn btn-sm dropdown-toggle padding-none" data-toggle="dropdown">  </button>
                <ul class="dropdown-menu checkbox-persist" role="menu">
                    <li class="menu-arrow">
                        <div class="menu-arrow-up"></div>
                    </li>
                    <li class="dropdown-header">Your Account <span class="pull-right glyphicons glyphicons-user"></span></li>
                    <li>
                        <ul class="dropdown-items">
                            <li>
                                <div class="item-icon"><i class="fa fa-envelope-o"></i> </div>
                                <a class="item-message" href="messages.html">Messages</a> </li>
                            <li>
                                <div class="item-icon"><i class="fa fa-calendar"></i> </div>
                                <a class="item-message" href="calendar.html">Calendar</a> </li>
                            <li class="border-bottom-none">
                                <div class="item-icon"><i class="fa fa-cog"></i> </div>
                                <a class="item-message" href="customizer.html">Settings</a> </li>
                            <li class="padding-none">
                                <div class="dropdown-lockout"><i class="fa fa-lock"></i> <a href="screen-lock.html">Screen Lock</a></div>
                                <div class="dropdown-signout"><i class="fa fa-sign-out"></i> <a href="<?php echo base_url('admin/logout'); ?>">Sign Out</a></div>
                            </li>
                        </ul>
                    </li>
                </ul>
            </div>