Adobe Flex Combobox DataProvider

Question

I have a project that was compiled with the Flex 3.2 SDK.

One of my components is a combobox, which is bound to a property (called products) in the Cairngorm model. If I insert a new value into model.products, then the combobox immediately shows the new value. Works perfectly.

I then moved to the 3.5 SDK, and running the identical operation causes a problem. Even though the model has been updated (I have verified that this is definately the case), the combobox does not show the new value correctly - it seems to be aware that there is a new item because there is a new row in the combo, but the new row is blank and unselectable. The existing items in the combo are there and selectable (as they should be). If I re-initialising the form (i.e. close and re-open the TitleWindow on which the combo is located), then all the correct values (including the new one) are shown in the combo.

I have swapped back and forth a few times between 3.2 and 3.5 to verify that this is indeed the root cause.

Any idea on how to get around this would be greatly appreciated.

Answer 1

Are you changing the dataProvider, or replacing it?

I have noticed that in the Flex 4 version of the Flextras AutoCompleteComboBox the ComboBox dataProvider sometimes get out of sync with the drop down's dataProvider. I figured this was all my fault due to the changes I made to add AutoComplete to the ComboBox.

It is entirely possible that this change was added in Flex 3.5; and I just didn't notice it until my Flex 4 adventures.

First, I'd try to invalidate the ComboBox when the dataProvider changes. You can do this by listening to the collectionChange event of the collection. In the event handler just do:

myCombo.invalidateProperties()
myCombo.invalidateDisplayList()

If you're repacing the dataPRovider, then you may try to override the set dataProvider method and add a line like this:

this.dropdown.dataProvider = value;

Is an odd issue. I believe in Flex 3 / 3.2 was that every time the dataPRovider changed the drop down was closed [destroyed] and re-created. It appears they stopped doing that at some point; which causes this anomaly.

Answer 2

//this will replace the list base on an update
private var newDropDown:ListBase;

//This addresses a bug in flex 3.5 SDK 
//where the list base does reflect changes to the data provider
//forums.adobe.com/thread/597632  
//bugs.adobe.com/jira/browse/SDK-25705 
//bugs.adobe.com/jira/browse/SDK-25567
override public function set dataProvider(value:Object):void
{
    super.dataProvider = value;
    newDropDown = dropdown;

    if(newDropDown)
    {
        validateSize(true);
        newDropDown.dataProvider = super.dataProvider;
    }
}