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Saturday, 19 February 2011

Visualforce Re-rendering Woes

A couple of days ago I was tripped up by re-rendering for what seemed like the hundredth time.  I'd created a page containing a conditionally rendered component based on a boolean field from the controller. This field was initially set to false, so the component didn't appear.  The value could then be changed on the page via a checkbox and clicking a button would refresh a section of the page whereupon the component would magically appear.  Here's a much reduced version of the Visualforce markup.

<apex:page controller="RerenderController">
<h1>Rerender Example</h1>
<apex:form >
  <apex:outputPanel id="datePanel" rendered="{!showdate}"> 
    <apex:outputText value="Date : {!todaysDate}"/>
  </apex:outputPanel>
  <div>
     Show Date? <apex:inputCheckbox value="{!showDate}"/>
  </div>
  <apex:commandButton value="Submit" rerender="datePanel"/>
</apex:form>
</apex:page>

I changed the value, clicked the button and hey presto - nothing changed!  I went the usual route of adding debug to the controller, which showed that the showDate value as being updated correctly.  Maybe there was an error that we being hidden due to the re-rendering, so out came the rerender attribute on the command button. No sign of any error and things started behaving as expected.  At this point I remembered why this is happening.

Adding the rerender attribute back in and viewing the source for the generated page shows the following:

<h1>Rerender Example</h1> 
<form id="j_id0:j_id2" name="j_id0:j_id2" method="post" action="https://kab-tutorial.na6.visual.force.com/apex/RerenderExample" enctype="application/x-www-form-urlencoded"> 
<input type="hidden" name="j_id0:j_id2" value="j_id0:j_id2" /> 
 
  <div> 
     Show Date?<input type="checkbox" name="j_id0:j_id2:j_id5" /> 
  </div><input class="btn" id="j_id0:j_id2:j_id7" name="j_id0:j_id2:j_id7" onclick="A4J.AJAX.Submit('j_id0:j_id2',event,{'similarityGroupingId':'j_id0:j_id2:j_id7','parameters':{'j_id0:j_id2:j_id7':'j_id0:j_id2:j_id7'} } );return false;" value="Submit" type="button" /><div id="j_id0:j_id2:j_id8"></div><input type="hidden"  id="com.salesforce.visualforce.ViewState" name="com.salesforce.visualforce.ViewState" value="..." />
<form>

Notice that there is no element with an id containing the text datePanel, as the output panel isn't rendered due to the showDate value being false. Thus even though the showDate value is set to true, when the Ajax request completes, the element that should be re-rendered doesn't exist and therefore nothing changes.

The solution is to nest the conditionally rendered output panel inside another output panel and change the command button to rerender that. The containing output panel will always be present on the page and thus the Ajax request will be able to update it on completion. The inner component may or may not be rendered depending on the value of showDate.

Below is the revised Visualforce markup that behaves as desired:

<apex:page controller="RerenderController">
<h1>Rerender Example</h1>
<apex:form >
  <apex:outputPanel id="datePanelContainer">
    <apex:outputPanel id="datePanel" 
        rendered="{!showdate}"> 
      <apex:outputText value="Date : {!todaysDate}"/>
    </apex:outputPanel>
  </apex:outputPanel>
  <div>
     Show Date? <apex:inputCheckbox value="{!showDate}"/>
  </div>
  <apex:commandButton value="Submit" 
    rerender="datePanelContainer"/>
</apex:form>
</apex:page>

33 comments:

  1. Thank you! This was very helpful.

    ReplyDelete
    Replies
    1. Hello Sir I want retrive 10 records in visualforce page with search button Accounts like (jon, heer, billclike, rams, geeet, siv, gramji, getea, sighn, oviessa) all records i retrived using with pageblock and Account name is one column and billing city second column I wand search button to add this vosual force page if i search "jo" to display jon related record only please give a code for search button in visualforce page

      Delete
  2. This helped debug a similar issue I was having. I had an apex:commandbutton calling a rerender of the outputText element it was inside of. The rerender failed because no ID was output to the HTML for the outputText element.

    I switched the rerender to the id of the apex:form element, and wa-la, it worked.

    Thanks for the suggestion.

    ReplyDelete
  3. Thanks for posting this. I had thought my problem was due to some combination of public/private/accessor settings when it actuality, it was good ole' AJAX. You just saved me another day of debugging.

    ReplyDelete
  4. fantastic post. Hope I could have been here earlier!
    Yesterday I tried so many things as my render was not working and finally got a solution at end of day.
    anyways fantastic post with source.

    ReplyDelete
  5. A+ post. Thanks for the info.

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  6. A brilliant blog indeed , its very clear and simple to understand. My Sincerer appreciation for a truly dedicated effort.

    ReplyDelete
  7. Had this happen before, don't mix your rendered and rerender!!!

    ReplyDelete
  8. Good one Bob. Fantastic analysis.

    ReplyDelete
  9. p.s- "div" is not accepeted I changed it to diva.
    Page should render component based on passed param each time. Once component rendered first time and component opens as overlay, upon closing component, page does not get refreshed. When calling "ViewRepDetail" next time it shows results from 1st rendered result from component. Any help would be much appreciated.
    Thanks-
    SG

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  10. can't post code.

    ReplyDelete
  11. Can you post this up to the developerforce visualforce board - that will allow you to post code.

    ReplyDelete
    Replies
    1. Bob, i am beginner and would like to know how did you debug to get the base code that you pasted in here and which helped you to find the issue and fixning it with double outputpanel.

      Delete
  12. Bob,
    my post goes here:

    http://boards.developerforce.com/t5/Visualforce-Development/Component-rendering-issue-with-actionFunction/td-p/446421

    Thanks
    SG

    ReplyDelete
  13. This comment has been removed by the author.

    ReplyDelete
  14. Bob,

    Is there any way I can do this using command button only and not using checkbox at all?

    I tried using without inputCheckbox and its not working ,












    Thanks
    Ali

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  15. This should work fine using a command button. Just set the Boolean property in the controller in the action method. I just used a checkbox for clarity.

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  16. Wow, Bob, thank you sooo much! I was well on my way to losing hair when I found this. Thank, thanks, thanks!

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  17. Thanks for Bob for this wonderful post. I was wondering why my page block table wasn't rendering.. Worked like charm!! Your a super star.. :)

    ReplyDelete
  18. Hi Bob,
    Nice Post

    Following is my reruirement
    i have 2 components in a page..

    1st component with all links -- Account,Contact
    2nd with all page block section -- Account section, contact section

    If user clicks on Account link ... only account section from 2nd component should be displayed
    If user clicks on Contact link ... only contact section from 2nd component should be displayed.

    I tried the above approach but didnt worked.
    You can check my post on

    http://salesforce.stackexchange.com/questions/17773/apex-componen
    t-rendering-pageblock-on-other-component/17776?noredirect=1#17776



    ReplyDelete
  19. sir i have developed a pege for adding contacts for account.in this i included save,cancel,addanotheraccount buttons .when addanotheraccount button is clicked same pageblock section has to be displayed as 2nd pageblock section

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  20. Very helpful info as always! Cheers, mate.

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  21. Thanks !! It was really helpful . I spent around 10 hours to solve the problem but it didnt work . Ur blog helped me !! Thanks again !! .

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  22. Bob -- One of the all-time most useful VF posts on the Internet. Every time I have some 'why doesn't this rerender' issue, I'm reminded of this post.

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  23. Grande Maestro!

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  24. Hi, I'm new at this... How would the controller look like? :|

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  25. Awesome....That worked

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  26. Thanks a ton for posting this. Helped to solve a issue that's been killing me for some time.

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  27. Bob - you know what's up! I ran into similar issue today and your post has resolved it. Thank you!

    ReplyDelete
  28. I am facing challenge for Custom css is not reflecting on rerender.

    ReplyDelete
  29. Thank you for the clear and succinct explanation. Much appreciated.

    ReplyDelete