的Joomla！ $ this-＆gt; get（'Pagination'）返回null

Question

我按照Joomla创建了hello world组件！组件教程。 这是helloworld.php中的administrator/component/helloworld/model模型：

<?php
/**
 * @package     Joomla.Administrator
 * @subpackage  com_helloworld
 *
 * @copyright   Copyright (C) 2005 - 2015 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */
// No direct access to this file
defined('_JEXEC') or die('Restricted access');

jimport('joomla.application.component.modellist');


/**
 * HelloWorldList Model
 *
 * @since  0.0.1
 */
class HelloWorldModelHelloWorlds extends JModelList
{
     /**
   * Items total
   * @var integer
   */
    var $_total = null;

  /**
   * Pagination object
   * @var object
   */
    var $_pagination = null;

    function __construct()
    {
        parent::__construct();

        $mainframe = JFactory::getApplication();

        // Get pagination request variables
        $limit = $mainframe->getUserStateFromRequest('global.list.limit', 'limit', $mainframe->getCfg('list_limit'), 'int');
        $limitstart = JRequest::getVar('limitstart', 0, '', 'int');

        // In case limit has been changed, adjust it
        $limitstart = ($limit != 0 ? (floor($limitstart / $limit) * $limit) : 0);

        $this->setState('limit', $limit);
        $this->setState('limitstart', $limitstart);
    }

    function getData()
    {
        // if data hasn't already been obtained, load it
        if (empty($this->_data)) {
            $query = $this->_buildQuery();
            $this->_data = $this->_getList($query, $this->getState('limitstart'), $this->getState('limit'));
        }
        return $this->_data;
    }

    function getTotal()
    {
      // Load the content if it doesn't already exist
        if (empty($this->_total)) {
            $query = $this->_buildQuery();
            $this->_total = $this->_getListCount($query);
        }
        return $this->_total;
    }

    function getPagination()
    {
      // Load the content if it doesn't already exist
        if (empty($this->_pagination)) {
            jimport('joomla.html.pagination');
            $this->_pagination = new JPagination($this->getTotal(), $this->getState('limitstart'), $this->getState('limit') );
        }
        return $this->_pagination;
    }
    /**
     * Method to build an SQL query to load the list data.
     *
     * @return      string  An SQL query
     */
    protected function getListQuery()
    {
        // Initialize variables.
        $db    = JFactory::getDbo();
        $query = $db->getQuery(true);

        // Create the base select statement.
        $query->select('*')
                ->from($db->quoteName('#__helloworld'));

        return $query;
    }
}

这是view.html.php中的administrator/views/helloworld：

<?php
/**
 * @package     Joomla.Administrator
 * @subpackage  com_helloworld
 *
 * @copyright   Copyright (C) 2005 - 2015 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE.txt
 */

// No direct access to this file
defined('_JEXEC') or die('Restricted access');

jimport('joomla.application.component.view');
jimport('joomla.html.pagination');


/**
 * HelloWorlds View
 *
 * @since  0.0.1
 */
class HelloWorldViewHelloWorlds extends JViewLegacy
{
    /**
     * Display the Hello World view
     *
     * @param   string  $tpl  The name of the template file to parse; automatically searches through the template paths.
     *
     * @return  void
     */
    function display($tpl = null)
    {
        // Get data from the model
        $this->items        = $this->get('Items');
        $this->pagination   = $this->get('Pagination');
        var_dump($this->pagination);

        // Check for errors.
        if (count($errors = $this->get('Errors'))) {
            JError::raiseError(500, implode('<br />', $errors));

            return false;
        }

        // Display the template
        parent::display($tpl);
    }
}

首先我在Joomla Tutorial上做所有事情并且不适合我，然后我按照JPagination文件但仍然分页返回null