NBT tag problems

[bcwadsworth]

Hello everyone:

I am having problems with adding and getting NBT tags off of a custom item.

When a BlockOre drops this item, a HarvestDropsEvent is fired:

@SubscribeEvent
public void GetCorrectOreDrops(HarvestDropsEvent event)
{
	if (event.block instanceof BlockOre)
	{

		//STOP NOW if Block is being silk touched
		if (event.isSilkTouching)
		{
			event.drops.clear();
			event.drops.add(Stack.S(event.block));
		}

		int nuggets = (event.world.rand.nextInt(16) + event.fortuneLevel * event.world.rand.nextInt(5) + 1);

		ItemStack stack = event.drops.get(0);
		stack = ORef.lumpOre.addOre((BlockOre) event.block, nuggets, stack);
		event.drops.set(0, stack);
		event.dropChance = 1.0F;
	}
}

 

This refers to a NBT adding script in the item (addOre):

public ItemStack addOre(BlockOre ore, int nuggets, ItemStack stack)
{
	NBTTagList taglist = (stack.stackTagCompound != null && stack.stackTagCompound.hasKey("Ores")) ? (NBTTagList) stack.stackTagCompound.getTag("BiggerDim") : new NBTTagList();
	NBTTagCompound tag = new NBTTagCompound();

	tag.setInteger("nuggets", nuggets);
	tag.setInteger("ore", ore.getIdFromBlock(ore));
	taglist.appendTag(tag);

	System.out.println(tag.getInteger("ore"));

	stack.stackTagCompound.setTag("Ores", taglist);

	return stack;
}

 

Whenever I harvest the block, the game crashes. What am I missing?

 

 

[hugo_the_dwarf]

This helped me understand NBT greatly "

 

But the issue is you are forgetting to check to see if the itemstack has a NBTTagCompound

 

if (itemStack.stackTagCompound == null) {
		itemStack.setTagCompound(new NBTTagCompound());
	}

 

you are probably getting a crash of something being null right? Watch the video and all will be revealed to you. (also the posted code snippet is how you make sure not to get a crash trying to add to a null object)

[bcwadsworth]

The actual crash comes from a ticking memory connection with a whole bunch of forge/minecraft code, but it is caused by a null pointer in

stack.stackTagCompound.setTag("Ores", taglist);

in the second code bit.

[MultiMote]

As hugo_the_dwarf said, you forgot to add null-check for stackTagCompound.