what does "addNotify" really do ???

Hi,

Can someone explain to me what does the "addNotify()" command do
in Panel (or Applet).

I have a problem in NT platforms. My applet does not refresh an
 inner layed canvas. The same applet works fine on Unix and Win95
 platforms.

 Only when i added "addNotify()" to the applet start()
  it solved the refresh problem.
 But, to my poor luck it caused a SEGMENTATION FAULT(!) both in the
 Unix appletviewer and Netscape 3.0.

thanks,
Avi Kavas.
kavasAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

gwaltersCommented:
The addNotify() method creates a peer for the given component.  A peer is a class which is responsible for the appearance of that component (where the component itself is responsible for its functionality).  Peers are usually (but don't have to be) native code.  It's really just a way of separating function from appearance (so a TextField, for example, functions the same on Unix and Windows, but it's appearance is platform-dependant).

Here is the addNotify() method from the Panel class:

public syncronized void addNotify() {
  peer = getToolkit().createPanel(this);
  super.addNotify();
}

You should never have to call addNotify() directly.  The fact that it fixed your problem is most likely a coincidence.  However, I can't imagine that calling it would cause SEGMENTATION FAULT.

One thing is that, if the start method never returns, the applet will never be shown.  This is because the browser calls start() and then show() on the applet.  It's a good idea to only do simple setup in the start() method and return.  If you really need a running thread for the life of your applet (most really don't: they just process events), then you can implement Runnable, and put all that code in the run() method.

Or you can call show() yourself, but it's still not a good idea to stay in start() indefinitely.

Sorry for the rambling!


0

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Java

From novice to tech pro — start learning today.

Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.