Looping through items in a Spark List control in Flex 4

5 Responses to Looping through items in a Spark List control in Flex 4

1. Michael Novotny says:

   February 5, 2010 at 8:30 am

   Peter : :

   I had a couple of questions on this post…

   1. I copy and pasted this example into a new Flex applcation and it ran perfectly. But then I changed “requestedRowCount” to 3 instead of 5, but it still showed 5. Any ideas why that would be?

   2. Then, for extra kicks, I tried to push this a bit further… One of the things that’s really bothered me and my company is how much extra work it takes to set the “requestedRowCount” on a DropDownList as written about in your blog post here last April (http://blog.flexexamples.com/2009/04/05/setting-the-row-count-on-a-dropdownlist-control-in-flex-gumbo/). So, for fun, I replaced s:List with s:DropDownList in this example to see if I could get away with significantly less code to pull off a “requestedRowCount”. I ran it and it sorta worked… The DropDownList opened and I saw only 3 items listed, but then it immediately hit a RTE (Error #1009: Cannot access a property or method of a null object reference.) in DropDownListBase on setting the “spDelta” on line 662 (the dataGroup was null). I’ve tried several things to “trick it” like giving it a DataGroup, but that results in other RTE’s due to there not being a “typicalItem” or invalid “dataGroupProperties” (I can give you more details on those RTE’s as well if you’d like). At any rate… It seems to me that if “requestedRowCount” work with list as it does in this example without an RTE, that it should in DropDownList too. Can you please explain why it’s necessary for two custom classes just to get “requestedRowCount” on a DropDownList?

   Thanks for your time in reading this and for doing these examples. They are invaluable! And, if it makes any difference in my question, the Flex 4 code we’re using at our company is around the 12073 revision mark from the Adobe repository. Thanks again and I look forward to your reply!

   : : Michael
   • Peter deHaan says:

     February 5, 2010 at 10:23 am

     @Michael,

     The requestedRowCount works fine for me in 4.0.0 (build 13895). I’m pretty sure we fixed that issue where the minHeight property on the Spark List skin was getting set to 112px (5 items+border if using default item renderer). You can get around the issue by creating a custom Spark List skin without the minHeight property set, or even better would be to download a newer Nightly build of the Flex 4.0 SDK from http://opensource.adobe.com/wiki/display/flexsdk/Download+Flex+4.

     As for question #2, I’d download the latest nightly build of Flex 4.0 SDK and try again, if you’re still seeing an RTE, I’d file a bug right away at http://bugs.adobe.com/flex/ and somebody at Adobe will take a look.

     Thanks,
     Peter
   • Peter deHaan says:

     February 5, 2010 at 10:37 am

     Actually, I looked at that mess of a post on Spark DropDownList and row counts, and I found a way easier way in the latest SDK (or maybe it always worked and I missed the obvious before). You can just override the layout property on the DropDownList and set the requested row count on the VerticalLayout object directly.

     <?xml version="1.0" encoding="utf-8"?>
     <s:Application name="Spark_DropDownList_layout_requestedRowCount_test"
             xmlns:fx="http://ns.adobe.com/mxml/2009"
             xmlns:s="library://ns.adobe.com/flex/spark">
         <s:controlBarContent>
             <s:CheckBox id="ch"
                     label="arrowKeysWrapFocus:"
                     selected="true" />
         </s:controlBarContent>
      
         <s:DropDownList id="lst"
                 requireSelection="true"
                 arrowKeysWrapFocus="{ch.selected}"
                 horizontalCenter="0" verticalCenter="0">
             <s:layout>
                 <s:VerticalLayout gap="0"
                         horizontalAlign="contentJustify"
                         requestedRowCount="2" />
             </s:layout>
             <s:dataProvider>
                 <s:ArrayList>
                     <fx:Array>
                         <fx:Object label="Application" />
                         <fx:Object label="BorderContainer" />
                         <fx:Object label="Button" />
                         <fx:Object label="ButtonBar" />
                         <fx:Object label="ButtonBarButton" />
                         <fx:Object label="CheckBox" />
                         <fx:Object label="ComboBox" />
                         <fx:Object label="DataGroup" />
                         <fx:Object label="DataRenderer" />
                         <fx:Object label="DropDownList" />
                     </fx:Array>
                 </s:ArrayList>
             </s:dataProvider>
         </s:DropDownList>
      
     </s:Application>

     Again, I tested in 4.0.0 (build 13895) and it worked like I expected, but please download the latest nightly build and make sure you’re still not seeing any runtime errors (and file a bug if you do).

     Thanks,
     Peter
     • Michael Novotny says:

       February 5, 2010 at 12:29 pm

       Peter : :

       Thanks for the prompt reply, for taking the time to revisit and test some things out, and for reposting an example. Copy and pasting the code above in your second reply into our environment still produces an RTE, but as I mentioned in my first post, we are on / around revision 12073. I will acquire the latest nightly build and report back. Thanks again for your help!

       : : Michael
     • Michael Novotny says:

       February 22, 2010 at 8:02 am

       Peter : :

       Sorry for the delay in getting back to you. We have been pretty busy prepping for the 1.0 release of our product.

       We upgraded our SDK last week to revision 14184. I retested this and it works perfectly (with the knowledge of the > 6 limitation because of the DropDownListSkin).

       Thanks for all your help on this!

       : : Michael