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JesseJ
PostPosted: Mon Mar 26, 2012 1:41 pm 
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Joined: Mon Mar 26, 2012 1:31 pm
Posts: 18
Not sure if this bug is specific to JBox2D, but it's what I'm using.

The game will run normally, but seemingly at random I get a NullPointerException within world.step(). There's probably a specific reason why this occurs, but I can't find it, nor do I have any idea where to look. Anyone have any ideas as to why this would even occur?
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Nitrooo
PostPosted: Mon Mar 26, 2012 4:21 pm 
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Try to add the jbox2d source code to your project and step into the World.step() method. Or just wait for the exception to be raised, then check the call stack and put some breakpoints.
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JesseJ
PostPosted: Tue Mar 27, 2012 8:43 am 
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Step into the method? With a debugger? But, as I said, it appears at seemingly random. If the program pauses every time it hits world.step(), I could be at it forever.
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Nitrooo
PostPosted: Tue Mar 27, 2012 9:14 am 
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1) Attach jbox2d source to your project
2) Run in debug mode
3) Wait for your random exception
4) Check the call stack
5) Put a conditional breakpoint on the excepting instruction (kind of "stop if var == null")
6) Rerun and wait for the debugger to stop
7) Guess what's wrong :D
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JesseJ
PostPosted: Wed Apr 11, 2012 2:51 pm 
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Well I got a stack trace, but it doesn't help me. I mean, I can see where in world.step() that it crashes, but I have no idea what I can do about it.


Code:
04-11 15:47:21.378: E/AndroidRuntime(5822): FATAL EXCEPTION: Thread-20
04-11 15:47:21.378: E/AndroidRuntime(5822): java.lang.NullPointerException
04-11 15:47:21.378: E/AndroidRuntime(5822):    at org.jbox2d.dynamics.ContactManager.addPair(ContactManager.java:73)
04-11 15:47:21.378: E/AndroidRuntime(5822):    at org.jbox2d.collision.broadphase.BroadPhase.updatePairs(BroadPhase.java:191)
04-11 15:47:21.378: E/AndroidRuntime(5822):    at org.jbox2d.dynamics.ContactManager.findNewContacts(ContactManager.java:155)
04-11 15:47:21.378: E/AndroidRuntime(5822):    at org.jbox2d.dynamics.World.solve(World.java:1017)
04-11 15:47:21.378: E/AndroidRuntime(5822):    at org.jbox2d.dynamics.World.step(World.java:560)
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toucansam
PostPosted: Wed Apr 11, 2012 3:04 pm 
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Joined: Mon Jun 08, 2009 12:21 pm
Posts: 353
which version of the engine are you running
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JesseJ
PostPosted: Wed Apr 11, 2012 3:39 pm 
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The name of the jar file has 2.1.2.
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toucansam
PostPosted: Wed Apr 11, 2012 4:05 pm 
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2.1.2.?
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JesseJ
PostPosted: Wed Apr 11, 2012 4:09 pm 
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Yes, 2.1.2
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toucansam
PostPosted: Wed Apr 11, 2012 4:56 pm 
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Sorry, 2.1.2.x, what is x?
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