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Re: Wierd AWT exception on loading graphics

On Sunday, Jul 6, 2003, at 18:24 America/New_York, David Leader wrote:
I've been sort of on holiday working on a small awt app (MetaFlux) under OS 9 (ide CodeWarrior 8) on my iBook reusing well-established code to load a background graphic. The app was fine until suddenly it started throwing the following run-time exception:

Exception Occurred:
java.lang.NullPointerException
at sun.misc.Cache.get(Cache.java)
at sun.awt.SunToolkit.getImageFromHash(SunToolkit.java)
at sun.awt.SunToolkit.getImage(SunToolkit.java)
...
at java.lang.Thread.run(Thread.java)

Toolkit.getImage() is wonky. It has to cache, because that's how Sun implemented it originally (for some reason), and now people are absolutely dependent on it. You should really use Toolkit.createImage() instead, as it doesn't cache. Yes, requires you to write some code. On the other hand, you will have control over what that code does, managing your resources.

It's easy for me to imagine that the setup of the cache in question could be easily screwed up by running code in a secondary thread before anything else in AWT was touched. Like I said, there is just sooooo much magic going on in AWT you have no control of ...

If you want to make the least number of changes in your code, I think I would try changing the way you are running your Runnable (via Thread.start(), presumably), to use EventQueue.invokeAndWait() or invokeLater() as appropriate. That way, the code will run on a Thread which AWT controls a bit more, and, in fact, >should< add a little more latency to the system, which will also help ensure the stuff needed to be set up, is actually set up.

email@hidden
Patrick Mueller
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 >Wierd AWT exception on loading graphics (From: David Leader <email@hidden>)



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