Cant access nested MovieClip AS3

Question

I'm trying to create a intro screen then a start screen after the intro screen is done playing.

I thought the easiest way of doing this would be on scene 1 frame 1, I would create a MovieClip.

By the way this is a separate document file. So I gave it a document class name of mcStartGameScreen and linked it to Flash Develop for actions.

Now the MovieClip that is on frame 1, I gave an instance name of startMenu then inside the startMenu MovieClip there is a MovieClip that I wanted the buttonMode enabled to be true. I add this MovieClip which is called mcStart on frame(65) inside my startMenu.

Now in my Actions I have this:

public class mcStartGameScreen extends MovieClip 
{

    private var mcStart:MovieClip;

    private var startMenu:MovieClip;

    public function mcStartGameScreen() 
    {
         startMenu.mcStart.buttonMode = true; //This is giving me the ERROR!

         mcStart.addEventListener(MouseEvent.CLICK, startOnClick);          
    }

    private function startOnClick(e:MouseEvent):void 
    {
         dispatchEvent(new Event("START_GAME"));
    }

    public function hideScreen():void
    {
         this.visible = false;  
    }

    public function showScreen():void
    {
         this.visible = true;
    }       
}

When I test the movie I get this error: Cannot access a property or method of a null object reference.

Does anyone know what I am doing wrong?

Answer 1

If you already have a MovieClip with instance name startMenu placed on the stage, so no need for,

private var startMenu:MovieClip; you remove this from your code.

And always have the stage instance first and then proceed.

So modify your constructor like so:

public function mcStartGameScreen() 
{
    addEventListener(Event.ADDED_TO_STAGE, onAddedToStage);
}

private function onAddedToStage(e:Event):void
{
    startMenu.mcStart.buttonMode = true; //Now this will not give the ERROR!

    startMenu.mcStart.addEventListener(MouseEvent.CLICK, startOnClick);
}