Adding a dynamically created DataGrid as child or element does not work - actionscript-3

Question

I am trying to develop an application in AS3. What I am really trying to achieve is to have only one datagrid and having it show, you say, three different set of datas. (the real count will be changing dynamically, and it does not matter as the problem is not relevant with this) Yes, it has to be only one datagrid because of you know, I need a compact interface.
The class "Sonuc" has three properties which are string versions of inputs from constructor. A typical "Sonuc" object is something like this.
var sonuc1:Sonuc = new Sonuc(1,1,false);
//sonuc1.num = "1"
//sonuc1.type = "1"
//sonuc1.isTrue = "No"
The reason that I have informed you about "Sonuc" class is that I wanted you to know that class was not something too complicated. And x.mxml is the test mxml where I only load the class for testing purposes.
This is what I have coded so far
public class ResultInterface extends UIComponent
{
private const desiredWidth:int = 250;
private const desiredHeight:int = 150;
private const sonuc1:Sonuc = new Sonuc(1,1,false);
public var tablo:DataGrid = new DataGrid();
public var kolonArray:Array = new Array ();
public var sonucArray:Array = new Array ();
public var currentIndex:int = new int ();
public var prevButon:Button = new Button();
public var nextButon:Button = new Button();
public function ResultInterface():void
{
currentIndex = 0;
super();
tablo = new DataGrid();
width=desiredWidth+40;
height=desiredHeight+60;
this.tablo.width = desiredWidth;
this.tablo.height = desiredHeight;
this.tablo.x = 20;
this.tablo.y = 40;
prevButon.x = 10;
prevButon.y = genislik/2 - 10;
prevButon.width =
prevButon.height = 10;
nextButon.x = genislik +20;
nextButon.y = genislik/2 -10;
nextButon.width =
nextButon.height = 10;
var referansColl:ArrayCollection = new ArrayCollection();
sonucArray.push(referansColl);
tablo.dataProvider = sonucArray[currentIndex];
var sampleCol:DataGridColumn = new DataGridColumn();
sampleCol.dataField = "num";
sampleCol.headerText = "Number";
var sampleCol2:DataGridColumn = new DataGridColumn();
sampleCol2.dataField = "type";
sampleCol2.headerText = "Type";
var sampleCol3:DataGridColumn = new DataGridColumn();
sampleCol3.dataField = "isTrue";
sampleCol3.headerText = "Is it true?";
kolonArray.push(sampleCol,sampleCol2,sampleCol3);
tablo.columns = kolonArray;
this.addElement(tablo); //**** this is the problematic line
this.addChild(oncekiButon);
this.addChild(sonrakiButon);
}
public function getNewSonuc(incoming:Sonuc):void
{
sonucArray[currentIndex].addItem(incoming);
}
public function newTablo():void
{
var newTablo:ArrayCollection = new ArrayCollection();
currentIndex = sonucArray.push(newTablo);
}
public function prev(evt:Event):void //I haven't written event listeners yet
{
if(currentIndex > 0)
currentIndex--;
nextButon.enabled = true;
if(currentIndex == 0)
prevButon.enabled = false;
}
public function birSonrakine(evt:Event):void
{
if(currentIndex < sonucArray.length)
currentIndex++;
prevButon.enabled = true;
if(currentIndex == sonucArray.length)
nextButon.enabled = false;
}
in this version, I get a syntax error "call to a possibly undefined method addElement"
I also tried having the base class as "Sprite" and "Canvas"
when I used addChild instead of addElement, then I get runtime error "addChild is not available to this class"
when I just commented the problematic line out, everything was loaded perfectly but the datagrid itself.
Note that error occurs before sending in some data (Sonuc) to datagrid.
and when I tried with canvas and with addelement, I get "Cannot access a property or method of a null object reference" with some weird functions and classes and packages.
1009: Cannot access a property or method of a null object reference.
at mx.styles::StyleProtoChain$/initProtoChainForUIComponentStyleName()[E:\dev\4.y\frameworks\projects\framework\src\mx\styles\StyleProtoChain.as:358]
at mx.styles::StyleProtoChain$/initProtoChain()[E:\dev\4.y\frameworks\projects\framework\src\mx\styles\StyleProtoChain.as:171]
at mx.core::UIComponent/http://www.adobe.com/2006/flex/mx/internal::initProtoChain()[E:\dev\4.y\frameworks\projects\framework\src\mx\core\UIComponent.as:10926]
at mx.core::UIComponent/regenerateStyleCache()[E:\dev\4.y\frameworks\projects\framework\src\mx\core\UIComponent.as:10989]
at mx.core::UIComponent/http://www.adobe.com/2006/flex/mx/internal::addingChild()[E:\dev\4.y\frameworks\projects\framework\src\mx\core\UIComponent.as:7465]
at mx.core::UIComponent/addChild()[E:\dev\4.y\frameworks\projects\framework\src\mx\core\UIComponent.as:7162]
at mx.controls.listClasses::ListBase/createChildren()[E:\dev\4.y\frameworks\projects\mx\src\mx\controls\listClasses\ListBase.as:3772]
at mx.controls::DataGrid/createChildren()[E:\dev\4.y\frameworks\projects\mx\src\mx\controls\DataGrid.as:1143]
at mx.core::UIComponent/initialize()[E:\dev\4.y\frameworks\projects\framework\src\mx\core\UIComponent.as:7634]
at mx.core::UIComponent/http://www.adobe.com/2006/flex/mx/internal::childAdded()[E:\dev\4.y\frameworks\projects\framework\src\mx\core\UIComponent.as:7495]
at mx.core::Container/http://www.adobe.com/2006/flex/mx/internal::childAdded()[E:\dev\4.y\frameworks\projects\mx\src\mx\core\Container.as:3974]
at mx.core::Container/addChildAt()[E:\dev\4.y\frameworks\projects\mx\src\mx\core\Container.as:2618]
at mx.core::Container/addChild()[E:\dev\4.y\frameworks\projects\mx\src\mx\core\Container.as:2534]
at mx.core::Container/addElement()[E:\dev\4.y\frameworks\projects\mx\src\mx\core\Container.as:2981]
at genel.siniflar::ResultInterfaceArayuz()[C:\Users\Ege\Adobe Flash Builder\brainswift2\src\genel\siniflar\ResultInterface.as:95]
at x()[C:\Users\Ege\Adobe Flash Builder\brainswift2\src\x.mxml:27]
at _x_mx_managers_SystemManager/create()[_x_mx_managers_SystemManager.as:54]
at mx.managers.systemClasses::ChildManager/initializeTopLevelWindow()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\systemClasses\ChildManager.as:311]
at mx.managers::SystemManager/initializeTopLevelWindow()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\SystemManager.as:3057]
at mx.managers::SystemManager/http://www.adobe.com/2006/flex/mx/internal::kickOff()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\SystemManager.as:2843]
at mx.managers::SystemManager/http://www.adobe.com/2006/flex/mx/internal::preloader_completeHandler()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\SystemManager.as:2723]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at mx.preloaders::Preloader/timerHandler()[E:\dev\4.y\frameworks\projects\framework\src\mx\preloaders\Preloader.as:542]
at flash.utils::Timer/_timerDispatch()
at flash.utils::Timer/tick()
I really need your help folks, please answer as soon as possible.

Answer 1

Well, I tried calling "addElement" from outside of the constructor, and it worked. However I don't know what did exactly cause this error and I know that my solution is not a legitimate one. And I would like to learn proper solution to this problem.
changes to resultInterface.as
// this.addElement(tablo); **** this is the problematic line, we have commented it out
this.addChild(oncekiButon);
this.addChild(sonrakiButon);
changes to x.mxml
public function onCreationComplete(evt:Event):void
{
showResult.addElement(showResult.tablo);
addElement(showResult);
}