title: Primefaces BlockUI is not working
body: <p>I am updating my datatable when a user clicks the menu. So I want to show some loading image while ajax fetches the data and updates my datatable. I am using p:blockUI for this purpose.
  My menu is : </p>
  
  <pre><code>&lt;h:form id="leftMenu"&gt;    
      &lt;p:menu id="privilegeItem"&gt;        
          &lt;p:menuitem id="objectItem" 
                      actionListener="#{selectSignMethodView.changeSignMethods('object')}" 
                      value="Object Signing Services" 
                      update=":signMethodForm:signMethodTable"/&gt;
          &lt;p:menuitem id="mobileItem" 
                      actionListener="#{selectSignMethodView.changeSignMethods('mobile')}" 
                      value="Mobile Signing Services" 
                      update=":signMethodForm:signMethodTable"/&gt;
          &lt;p:menuitem id="macItem" 
                      actionListener="#{selectSignMethodView.changeSignMethods('mac')}" 
                      value="Mac Signing Services" 
                      update=":signMethodForm:signMethodTable"/&gt;     
          &lt;p:menuitem id="solarisItem" 
                      actionListener="#{selectSignMethodView.changeSignMethods('solaris')}" 
                      value="solaris Signing Services" 
                      update=":signMethodForm:signMethodTable"/&gt;  
      &lt;/p:menu&gt;
  &lt;/h:form&gt;
  </code></pre>
  
  <p>And my datatable is like this : </p>
  
  <pre><code>&lt;h:form prependId="false" id="signMethodForm"&gt; 
      &lt;p:dataTable id="signMethodTable" 
                   value="#{selectSignMethodView.signMethodList}" 
                   var="signMethods"&gt;
          &lt;p:column&gt;
              &lt;h:outputText value="${signMethods.name}"/&gt;
          &lt;/p:column&gt;
          &lt;p:column&gt;
              &lt;h:outputText value="#{signMethods.fileTypes}" /&gt;
          &lt;/p:column&gt;
          &lt;p:column&gt;
              &lt;h:outputText value="#{signMethods.servers}"/&gt;
          &lt;/p:column&gt;
      &lt;/p:dataTable&gt;
      &lt;p:blockUI trigger=":leftMenu:privilegeItem" block="signMethodTable"&gt;
          LOADING&lt;br /&gt;
          &lt;p:graphicImage library="images" name="ajax-loader.gif"/&gt;
      &lt;/p:blockUI&gt;
  &lt;/h:form&gt;
  </code></pre>
  
  <p>But blockUI is not blocking my datatable . Is something wrong with my trigger attribute.</p>