问PF DataTable过滤器功能不起作用

EN

<h:form>
    <p:dataTable var="pres" value="#{presBean.presentations}" rows ="10"
    paginator="true" paginatorTemplate="{CurrentPageReport} {FirstPageLink} {PreviousPageLink} {PageLinks} {NextPageLink} {LastPageLink} {RowsPerPageDropdown}"
    rowsPerPageTemplate="10,25,100" widgetVar="presTable" **filteredValue="#{presBean.filteredPres}"**>

    <p:column headerText="Title" sortBy="#{pres.title}">
    <!--f:facet name="header" sortBy="#{pres.title}">
        <h:outputText value="Title" />
    </f:facet-->
    <h:outputText value="#{pres.title}" />
</p:column>
<p:column headerText="Presenter" sortBy="#{pres.presenter}">
    <!--f:facet name="header">
        <h:outputText value="Presenter" />
    </f:facet-->
    <h:outputText value="#{pres.presenter}" />
</p:column>
</h:form>