Actionscript and ViewStack = Cannot access a property or method of a null object reference

Question

I'm writing a flex program in an OO manner and I've got to the point of creating a ViewStack to hold various panels. My problem is that when I add a panel to the ViewStack it throws the aforementioned error. No doubt the answer is pretty obvious so here's the constructor for the manager class that holds my ViewStack.

stack = new ViewStack();
loginPanel = new LoginPanel;
regPanel = new RegisterPanel;
stack.creationPolicy = "all";
stack.addChild(loginPanel);
stack.currentState = "loginPanel";

Answer 1

I'm not sure why you are setting the currentState property of the ViewStack. Are you trying to select that child? If so, try using the selectedChild property instead. This should work:

{
    stack = new ViewStack();

    loginPanel = new LoginPanel();

    regPanel = new RegisterPanel();

    stack.creationPolicy = "all";

    stack.addChild(loginPanel);

    stack.selectedChild = loginPanel;
}

Answer 2

Why its not possible to easyly access Elements that are inside any ViewStack ? AHHRRRGGGHH !!