/**
  * 获取列表
  * 
  * $offset
  * $count
  * $activity_id
  * $is_published
  * $is_completed
  */
 public function indexAction()
 {
     $offset = $this->getRequest()->getParam('offset', 0);
     $count = $this->getRequest()->getParam('count', 20);
     $activityId = $this->getRequest()->getParam('activity_id');
     // not used
     $isPublished = $this->getRequest()->getParam('is_published');
     $isCompleted = $this->getRequest()->getParam('is_completed');
     $condition = array('activity_id' => $activityId);
     $mSub = new Application_Model_SubActivity();
     $rs = $mSub->getSearch($condition, $count, $offset);
     echo json_encode($rs);
 }