动态改变datagrid column显示顺序

public function set ColumnOrder(arr:Array)
		{
			var aColumnsNew:Array = columns;
			for each(var columnname:Object in arr)
			{
				
				var column:DataGridColumn=new DataGridColumn;
				column.dataField=columnname.dataField;
				column.headerText=columnname.headerText;
				aColumnsNew.push(column);
			}
			columns=aColumnsNew;
			//必须要这么写，否则不能够出来效果；