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Japplet reloading from refresh

Posted on 2004-08-28
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Last Modified: 2008-02-01
Is there anyway to prevent an applet from reloading due to a refresh, or to disable the refresh?  Thanks experts.
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Question by:kesea
11 Comments
 
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girionis earned 500 total points
ID: 11923322
I do not think you can do it. Only way you can do (and only in IE) is to get an administrator to get rid of everything on the top bar (apart the URL address). But again the user can refresh if he clicks on F5.
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Expert Comment

by:girionis
ID: 11923328
What exactly are you trying to achieve?
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Author Comment

by:kesea
ID: 11923337
Oh a little more information, I have a frameset with two frames, I have a JApplet in first Frame and a my website in the second one.  If I hit refresh though the JApplet in the first page reloads and I don't what that to happen, how can I prevent the first Frame from Refreshing, or else the JApplet from Reloading?  Thanks experts.

Kes.
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LVL 35

Expert Comment

by:girionis
ID: 11923358
How do you reaload through the applet? You might be able to reload the frame is you sent the request and then you specify as target the second frame. But there is no way you can prevent the applet from refreshing if the user hits F5.
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Author Comment

by:kesea
ID: 11923365
You can just make the one frame in the frameset reload?
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Author Comment

by:kesea
ID: 11923370
Oh and I am not reloading through the applet, I am trying to prevent the applet from reloading if the user hits F5.  I have the Japplet spawn some Jframes, but if the user hits F5 then my JFrames will disappear.  :(  I want to prevent this.
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Expert Comment

by:girionis
ID: 11923395
> Oh and I am not reloading through the applet, I am trying to prevent
> the applet from reloading if the user hits F5.  I have the Japplet
> spawn some Jframes, but if the user hits F5 then my JFrames will
> disappear.  :(  I want to prevent this.

You cannot prevent it. F5 loads the whole page. I was thinking that you could send a specific request to the second frame but this is different to hitting F5.
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Expert Comment

by:objects
ID: 11923454
You control what happens when your applet is (re)loaded so you should handle it appropriately.

> but if the user hits F5 then my JFrames will disappear.

Why doesn't it reappear again?
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Expert Comment

by:Webstorm
ID: 11925329
Hi kesea,

JVM generally use applet caches to avoid reload of applet code.
When you hit F5, in fact the applet is stopped and restarted again (stop() and start() methods).
I don't know if it's possible, but you can try to manage the page reloading in the applet like:

public class myJApplet extends JApplet
{
    private boolean started=false,initialized=false;

    public void init()
    {
         if (!initialized)
         {
               initialized=true;
               // ...
         }
    }

    public void destroy()
    {
          // destroy nothing
    }

    public void start()
    {
         if (!started)
         {
               started=true;
               // ...
         }
    }

    public void stop()
    {
          // don't stop the applet
    }
}

It should work if the same applet instance is used when you reload the page. The applet may be hidden during reloading. But reloading should be quicker if you avoid destroying the applet resources and reloading them again.

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LVL 4

Expert Comment

by:omry_y
ID: 11925858
you can't do anything to stop the applet from reloading since when you hit F5, the browser really destroy your applet and re-initialize it.
since you mantioned JApplet, I assume you are using Sun's java plugin;
at least for later versions (1.4+) , when you refresh - your applet gets a new class loader, so even static fields in your classes are lost -
so storing state in static variables will not work.
you need to somehow store your state persistently when your applet goes does, and reload it when it starts.
if your applet is sigined, you can store state on the disk, if its not - you can store state on the server using some serverside component, its a bit complicated.
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Expert Comment

by:girionis
ID: 11994219
:)
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