[1.7.10] [Solved] Potion#performEffect leads to Null Pointer Error?

[IceMetalPunk]

I have a fluid block that, when the player touches it, should give them random status effects until they stop touching it. However, upon colliding with the block, it instead crashes the game with a Null Pointer Error. Which I can't figure out, because if I comment out just the line that calls Potion#performEffect, there are no crashes or errors, but some debug output confirms that the potion instance and the player are both not null, so what could possibly be null?

 

Here's the code:

 

	public void onEntityCollidedWithBlock(World world, int x, int y, int z, Entity ent) {
	if (world.isRemote || ent == null || !(ent instanceof EntityLivingBase)) {
		return;
	}
	EntityLivingBase player = (EntityLivingBase) ent;
	int potID = world.rand.nextInt(Potion.potionTypes.length);
	Potion pot = Potion.potionTypes[potID];
	System.out.println("Potion " + pot + ", Player " + player); // Debug output
	pot.performEffect(player, 0);
}

 

If I comment out just that last line, the crash doesn't happen, but of course no status effects are applied. Just before the crash, it outputs the debug message showing that "pot" is an instance of Potion, and "player" is an instance of EntityPlayerMP. So where's the null value here?

 

(Note: I'm not 100% sure what the second parameter to performEffect is; it looks like it's the level, so I put 0 for level 1, but I also tried with 40 on the guess it might actually be tick duration; that crashed just the same.)

[jeffryfisher]

You can either step into the call using the debugger or post (in spoiler tags) the crash report.

[Draco18s]

Also, some potion effects will be utterly harmless when you tick them once (poison, hunger, slowness, weakness, fatigue, wither) while others will be super deadly (instant damage).

[IceMetalPunk]

Not all potionIDs are valid. You need to check if there is a potion with that ID before you use it. What I mean is: Potion.potionTypes it not completely filled with potions, there are null entries for IDs that do not exist.

 

>_< D'oh! That seems to have solved the problem. Apparently, when it was crashing, it wasn't even outputting the null potion in the debug message first for some reason. I just added a check to return if pot==null, and it works. Go figure. Thank you!

 

Also, some potion effects will be utterly harmless when you tick them once (poison, hunger, slowness, weakness, fatigue, wither) while others will be super deadly (instant damage).

 

Yes, balancing will be done through a whitelist/blacklist of effects. I just haven't yet determined which effects should stay and which should go yet; that'll be future work. I'm probably going to end up using addPotionEffect instead after all, but I'm still glad I made this topic because without the explicit check for null potions, it'd still have had this same problem.

 

Thanks, everyone!