Using more than 1 xml file

Question

I have this one as file that is going to be doing most of the work eventually.  However, I am setting it up so that it uses another class file which is below this one.  My problem is that I cannot get this to work so that all four xml files come in before the loading function gets accessed and therefore the output tells me that it cannot access a null reference.  Then it loads the variables.  How do I get it so that the variables load and then the loading function fires? I have also connected the files so that they can be lloked at and run.  The fla is simple just create one and set the document class to Main in the properties area.
Here is the output.
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Main/loading()
at Main/init()
at Main()
Then the xmlData parts list.
Main.as
package
import flash.display.*;
import flash.events.*;
import flash.net.*;// brings in functions  or classes that are needed
import flash.net.URLLoader;// brings in functions to load in external data
import flash.net.URLRequest;// brings in functions that allow transfer from one variable to another
public class Main extends MovieClip
  public var football:XMLClass = new XMLClass("football.xml", "football");
  public var baseball:XMLClass = new XMLClass("baseball.xml", "baseball");
  public var basketball:XMLClass = new XMLClass("basketball.xml", "basketball");
  public var hockey:XMLClass = new XMLClass("hockey.xml", "hockey");
  public var pictures01:Loader = new Loader();
  public var pictures02:Loader = new Loader();
  public var pictures03:Loader = new Loader();
  public var pictures04:Loader = new Loader();
  public function Main()
  init();
  public function init()
   addChild(pictures01);pictures01.x = 25; pictures01.y = 25; pictures01.visible = true;
   addChild(pictures02);pictures02.x = 250; pictures02.y = 25; pictures02.visible = true;
   addChild(pictures03);pictures03.x = 475; pictures03.y = 25; pictures03.visible = true;
   addChild(pictures04);pictures04.x = 700; pictures04.y = 25; pictures04.visible = true;
loading(4);
    loading(4);
  public function loading(sent:Number)
   trace("got to function loading");
   //trace(football.xmlData.football.team[sent], baseball.xmlData.baseball.team[sent], basketball.xmlData.basketball.team[sent],hockey.xmlData.hockey.team[sent]);
   trace("got here 1");
   pictures01.load(new URLRequest(football.xmlData.team[sent].logo));// sets the b loader to hold the picture of the current book cover
   /*trace("got here 2");
   pictures02.load(new URLRequest(baseball.xmlData.team[sent].logo));// sets the b loader to hold the picture of the current movie cover
   trace("got here 3");
   pictures03.load(new URLRequest(basketball.xmlData.team[sent].logo));// sets the b loader to hold the picture of the current poster
   trace("got here 4");
   pictures04.load(new URLRequest(hockey.xmlData.team[sent].logo));// sets the b loader to hold the picture of the current poster
   trace("got here 5");*/
   trace("able to end loading function");
  }// end of loading function
XMLClass.as
package
import flash.display.*;// brings in functions  or classes that are needed
import flash.events.Event;// brings in functions  or classes that are needed
import flash.events.MouseEvent;// brings in functions  or classes that are needed
import flash.net.*;// brings in functions  or classes that are needed
import flash.net.URLLoader;// brings in functions to load in external data
import flash.net.URLRequest;// brings in functions that allow transfer from one variable to another
/* creates the class and sets memory area for the various parts */
public class XMLClass
  public var filename:String = new String();
  public var mainElement:String = new String();
  public var xmlLoader:URLLoader = new URLLoader();// sets up a new variable to load in the XMl data that is only to be used by this class
  public var xmlData:XML;//declares the variable that holds the information loaded in the URLLoader that is only to be used by this class
  public var xmlList:XMLList = new XMLList();//sets a variable that handles the listing of the XMLdata variable that is only to be used by this class
public function XMLClass(string1:String,string2:String)
   filename = string1; trace("got to set filename " + filename);
   mainElement = string2; trace("got to set mainElement " + mainElement);
   this.xmlLoader.load(new URLRequest(filename)); trace("got to load new URLRequest");// looks for the file named in order to load it and then loads it
   this.xmlLoader.addEventListener(Event.COMPLETE, useXML);// sets the xmlLoader variable to be aware of the XML file to see if it has finished getting loaded into the program
public function useXML(e:Event):void
  this.xmlData=new XML(e.target.data); trace("set up " + filename + " xmlData");//with the xml download complete populate the xmlData variable
  this.xmlList=xmlData.(mainElement); trace("setup " + mainElement + " xmlList");//pass the elements of the xml data file into a list
  trace(xmlData.(mainElement).team.*);

Answer 1

Sorry, I did not realize that.  I did the download so that you could see what I was
up to.  I forget that you're more experienced than I and can see things easier.  Anyway, here are the parts that matter. and I would like to know where the connection is going wrong.
This is the custom class that I created.
package 
  import flash.events.*;
  public class MyEventMaker extends EventDispatcher
    private static var dispatcher:MyEventMaker = null;
    public function MyEventMaker(enforcer:MyEventEnforcer) : void
      if(!enforcer)
       throw new Error("Direct instantiation is not allowed");
      return;
    }// end function
    public static function GetInstance() : MyEventMaker
      if(!dispatcher)
        dispatcher= new MyEventMaker (new MyEventEnforcer());
      }// end if
      return dispatcher;
    }// end function
class MyEventEnforcer{}
These are the lines in the XMLClass that is supposed to throw the event.
import MyEventMaker;
MyEventMaker.GetInstance().dispatchEvent(new WorkerEvent());
And this is the part in the actual class program that listens for the custom class event.
     myEventMaker.GetInstance().addEventListener(WorkerEvent.UNREACHABLE_EVENT, checkCount);
   myEventMaker.GetInstance().addEventListener(WorkerEvent.UNREACHABLE_EVENT, checkCount);
   myEventMaker.GetInstance().addEventListener(WorkerEvent.UNREACHABLE_EVENT, checkCount);
   myEventMaker.GetInstance().addEventListener(WorkerEvent.UNREACHABLE_EVENT, checkCount);
   if(variableCount >= 4){
    init();