Rerender a pageBlock if a value is entered in an inputField?

Question

I want to rerender a pageBlock by checking whether the inputField is null. If it is not null, then it should rerender the pageblock. I wrote the code, but the page block which needs to be rendered is not getting displayed.

my code

<apex:page standardController="Event" extensions="CVFC_EventPage_ctrl_Dev" >
 <apex:form >  
  <apex:pageBlock >
     <apex:pageBlockSection >
         <apex:inputField value="{!Event.Ownerid}" />
         <apex:inputField value="{!Event.Subject}"/>             
         <apex:inputField value="{!Event.IsAllDayEvent}"/>
         <apex:inputField value="{!Event.StartDateTime}"/>
         <apex:inputField value="{!Event.EndDateTime}"/>
         <apex:inputField value="{!Event.WhatId}"/>
         <apex:inputField value="{!Event.WhoId}"/>
         <apex:inputField value="{!Event.IsPrivate}"/>
         <apex:inputField value="{!Event.Location}"/>                         
     </apex:pageBlockSection>         
     <apex:pageblockButtons >
         <apex:commandButton value="Save" action="{!saveAndNew}"/>
     </apex:pageblockButtons>         
  </apex:pageBlock>

  <apex:pageBlock rendered="{!Event.Ownerid != ''}">
     <apex:pageBlockSection id="Event_view"  title="Event View" >
         <apex:inputField value="{!Event.Subject}"/>
     </apex:pageBlockSection>
  </apex:pageBlock>

When I remove rendered="{!Event.Ownerid != ''}" from the pageBlock it gets displayed, otherwise it does not. Can anybody tell me what might be the issue?

Answer 1

You do not have any code in your example that will rerender anything. All you have is the rendered attribute which is only determined when the page is originally loaded. You should try using the apex:actionSupport Visualforce functionality. Your page would look something like:

<apex:page standardController="Event" extensions="CVFC_EventPage_ctrl_Dev" >
 <apex:form >  
  <apex:pageBlock >
     <apex:pageBlockSection >
         <apex:inputField value="{!Event.Ownerid}">
             <apex:actionSupport event="onchange"
                                rerender="blockToRerender"/>
         </apex:inputField>
         <apex:inputField value="{!Event.Subject}"/>             
         <apex:inputField value="{!Event.IsAllDayEvent}"/>
         <apex:inputField value="{!Event.StartDateTime}"/>
         <apex:inputField value="{!Event.EndDateTime}"/>
         <apex:inputField value="{!Event.WhatId}"/>
         <apex:inputField value="{!Event.WhoId}"/>
         <apex:inputField value="{!Event.IsPrivate}"/>
         <apex:inputField value="{!Event.Location}"/>                         
     </apex:pageBlockSection>         
     <apex:pageblockButtons >
         <apex:commandButton value="Save" action="{!saveAndNew}"/>
     </apex:pageblockButtons>         
  </apex:pageBlock>

  <apex:outputPanel id="blockToRerender">
      <apex:pageBlock rendered="{!ISBLANK(Event.OwnerId)}">
         <apex:pageBlockSection id="Event_view"  title="Event View" >
             <apex:inputField value="{!Event.Subject}"/>
         </apex:pageBlockSection>
      </apex:pageBlock>
  </apex:outputPanel>

There are going to be a few issues with this though as this is a lookup field and the Javascript that fires off of it is a bit tricky.

Also, you may have some issues with the OwnerId actually getting set in the controller. I just can't seem to remember right now if these values are posted back to the server from an apex:actionSupport right now or not. Someone feel free to correct me if my assertion that they do get posted is incorrect.

Hopefully this helps you get moving in the right direction.