动态填充组合框（Flex）

Question

I want to populate a ComboBox after a clicked a button.

This is my code:

    var dpNames:ArrayCollection = new ArrayCollection();
    for each(var ca:Categorie in arrCategories)
    {
          dpNames.addItem ({label: ca.name, data: ca.value});
    }       

    cbWijzigCategorie.dataProvider = dpNames;

But when he executes the last line, I alwas get the following error:

TypeError: Error #1009: Cannot access a property or method of a null object reference.

I have no idea why.

Thanks a lot, Vincent

Answer 1

    private function categorieItemClick(evt:ItemClickEvent):void
    {

            var dpNames:ArrayCollection = new ArrayCollection();
            for each( var ca:Categorie in arrCategories)
            {
                dpNames.addItem ({label: ca.Name, data: ca.Name});
            }                   
            cbWijzigCategorie.dataProvider = dpNames;


    }



<mx:ButtonBar 
        x="10" y="36" 
        id="tbtnbarCategorie" 
        dataProvider="vsCategorie" 
        itemClick="categorieItemClick(event)">
</mx:ButtonBar>

    <mx:ViewStack 
        x="10" y="64" 
        id="vsCategorie" 
        width="601" height="343">

           <mx:Canvas label="Wijzig categorie" 
        id="cnvsChangeCategorie" 
        width="100%" height="100%">
        <mx:Label 
        x="10" y="10" 
        text="Kies categorie"/>
             <mx:ComboBox 
        x="101" y="8" 
        id="cbWijzigCategorie"></mx:ComboBox>
           </mx:Canvas>

    </mx:ViewStack>

Answer 2

Is your combobox instanciated? Looking at the error message, the problem would come from "cbWijzigCategorie.datprovider". It cannot access the dataprovider property cause cbWijzigCategorie is null.

Where are you assigning the dataprovider to the combobox? Inside the or outside the component?

Regards.

Answer 3

确保arrCategories不为空并且已正确初始化。