myDropDownList.as

/***
 *      POG - two-way
 *      databind no dropdownlist
 *      versao 0.1
 *
 */

package components
{
    import mx.collections.IList;
    import mx.controls.Alert;
    import mx.utils.ObjectUtil;

    import spark.components.DropDownList;

    public class myDropDownList extends DropDownList
    {
        public function myDropDownList()
        {
            super();
        }

        //Campo que será utilizado na pesquisa dentro do dataProvider
        [Bindable]
        public var keyField:String = "cCdId";

        //Campo usado para realizar o bind com a tabela.
        private var _keyValue:*;

        [Bindable]
        public function get keyValue():*
        {
            return _keyValue;
        }

        public function set keyValue(value:*):void
        {
            _keyValue = this.getKeyValue(value);

        }

        private function getKeyValue(value:*):*
        {
            if (value == null)
            {
                selectedIndex = -1;
                return;
            }
            for each (var obj:Object in dataProvider)
            {
                if (ObjectUtil.compare(obj[keyField].toString(), value) == 0)
                {
                    selectedIndex = dataProvider.getItemIndex(obj);
                    return obj[keyField].toString();
                }
            }
        }

        override public function set dataProvider(value:IList): void
        {
            super.dataProvider = value;

            if (keyValue != null)
            {
                keyValue = this.getKeyValue(selectedItem[keyField]);
            }
        }
    }
}