yii 搜索框无法搜索内容 [ 1.1 版本 ]

前台：

array(
    'name'=>'username',
    'header'=>Yii::t('user','Username'),
    'type'=>'raw',
    'htmlOptions'=>array('class'=>'center'),
    'value'=>'$data->user->username',
),

模型：

public $username;
public function rules()
{
    return array(
        array('realName, address, email, mobile, telephone, rebateCardNumber', 'required'),
        array('rebateCardNumber', 'numerical', 'integerOnly'=>true),
                array('rebateCardNumber,username, balance', 'safe', 'on'=>'search'),
        );
}
public function relations()
{

    return array(
            'user'=>array(self::BELONGS_TO, 'User', array('userid'=>'id')),
    );
}

public function search()
{
    $criteria=new CDbCriteria;	
    $criteria->with = array('user');  
    if(Rights::getAssignedRole(Yii::app()->user->id, 'Agents')) {
        $criteria->addCondition('userid !='.Yii::app()->user->id);
    }
    $criteria->addCondition('user.type=2');
    $criteria->compare('user.username',$this->username,true);
    $criteria->compare('realName',$this->realName,true);
    $criteria->compare('address',$this->address,true);
    $criteria->compare('email',$this->email,true);
    $criteria->compare('mobile',$this->mobile,true);
    $criteria->compare('telephone',$this->telephone,true);
    $criteria->compare('rebateCardNumber',$this->rebateCardNumber);
    $criteria->compare('balance',$this->balance);
    return new CActiveDataProvider($this, array(
        'criteria'=>$criteria,
    ));
}

搜索框已存在，但输入值无效，提交还是原来样子。原因是为什么？怎么解决？