[flexcoders] Why would mx.controls.NavBar.dataProvider not accept an array of DisplayObject? (3.0.0)

[Fiouz]

Hi,

I'd like to specify a custom Array dataProvider to a
mx.controls.ButtonBar instead of binding it to a ViewStack instance.
I'm doing the following:

            var array:Array = new Array();
            array.push(chart); // chart is a DisplayObject instance
            array.push(grid); // grid is a DisplayObject too
            buttons.dataProvider = array;

... but NavBar.dataProvider (ButtonBar extends NavBar) doesn't seem to
like this array of DisplayObject and throws an error, as seen in
NavBar source code: (Flex 3.0.0)

        else if ((value is IList && IList(value).length > 0 &&
                 IList(value).getItemAt(0) is DisplayObject) ||
                 (value is Array && (value as Array).length > 0 &&
                 value[0] is DisplayObject))
        {
            var name:String = id ?
                              className + " '" + id + "'" :
                              "a " + className;
            message = resourceManager.getString(
                                "controls", "errWrongType", [ name ]);
                        throw new Error(message);
        }

What is the reason behind throwing an error when an array of
DisplayObject is given? Why would I have to wrap my DisplayObject
instances in order to prevent this error?

Thanks in advance,

Regards.
-- 
Fiouz