DataGrid itemrender

Question

Hi i have added a control with the help itemrender in my datagrid. but there is a problem that in time of execution it comes two times at init and creation complete event of that control which i added in my datagrid column.

Thanks Atul Yadav

<?xml version="1.0" encoding="utf-8"?>
<mx:DataGridColumn xmlns:mx="http://www.adobe.com/2006/mxml" xmlns:ns1="Component.*" >
<mx:Script>
    <![CDATA[
        [Bindable]
        public var columnID:String="";
        [Bindable]
        public var ColumnData:String="";
]]>
</mx:Script>
     <mx:itemRenderer>
        <mx:Component>
        <ns1:test >
        </ns1:test>
        </mx:Component>
    </mx:itemRenderer>
</mx:DataGridColumn>

and my control code:

<?xml version="1.0" encoding="utf-8"?>
<mx:VBox xmlns:mx="http://www.adobe.com/2006/mxml" width="400" height="300" xmlns:ns1="View.*" creationComplete="init(event)">
<mx:Script>
    <![CDATA[
        import mx.controls.Alert;
        private static var arr:Array;
        private function init(e:Event):void{
            if(!arr)
                arr=new Array();
            arr.push(this);
            btn_apply.addEventListener(MouseEvent.CLICK,function(e:Event):void{Alert.show(arr.length.toString());});
        }
    ]]>
</mx:Script>
    <mx:Button label="Button" id="btn_apply"/>


</mx:VBox>

when i get arr length it gives me just double count.

Answer 1

If I understand correctly the second code snippet is your custom item renderer that is instantiated as <ns1:test> in the first snippet.

The DataGrid control will create instances of your renderer as and when it sees fit - you don't really have any control of how many instances will get created. So while you may have one row in the column the Data Grid is quite likely to have created more than one instance of the renderer component. The result, as you can see, is that creation complete is called more than once and you are getting more items in your static array than you are expecting. When developing item renderers you have to take into account that: you don't control their instantiation and that they are recycled by the framework. The best approach to take is to make them as stateless as possible.