Jump to content
Search In
  • More options...
Find results that contain...
Find results in...

[1.16] Backpack item that inventory size changes depending on a certain enchantment level


Recommended Posts

I'm trying to make a backpack item that inventory size changes depending on a certain enchantment level. For this reason, I would like to resize the inventory of the item stack when enchantments are granted or cleared. Is there an event that is commonly called for them? Is there no choice but to do enchantments by gold floor, enchantment table, command, etc. at each event? Or should I always check the item's enchantment level and inventory size on every tick?

Link to comment
Share on other sites

Yes. The itemstack may be in the player's inventory or dropped as an item entity. At least, what's the best way to drop an overflowing item when the enchantment is stripped with a grindstone?

Link to comment
Share on other sites

public void inventoryTick(ItemStack stack, World worldIn, Entity entityIn, int itemSlot, boolean isSelected) {
	if (!worldIn.isRemote()) {
		if (stack.getItem() != UMUBackpackItems.BACKPACK.get()) return;
		if (!(entityIn instanceof PlayerEntity)) return;

		IItemHandler inv = stack.getCapability(CapabilityItemHandler.ITEM_HANDLER_CAPABILITY).orElseThrow(RuntimeException::new);
		int size = BackpackItem.getSizeFromLevel(EnchantmentHelper.getEnchantmentLevel(Enchantments.BACKPACK_CAPACITY, stack));

		if (inv.getSlots() == size) return;

		entityIn.sendMessage(new StringTextComponent("slot:" + inv.getSlots()), null);
		entityIn.sendMessage(new StringTextComponent("size:" + size), null);

		NonNullList<ItemStack> oldInv = NonNullList.withSize(inv.getSlots(), ItemStack.EMPTY);
		for (int i = 0; i < inv.getSlots(); i++) {
			oldInv.set(i, inv.getStackInSlot(i));
		((ItemStackHandler) inv).setSize(size);

		for (int i = 0; i < inv.getSlots(); i++) {
			if (i < oldInv.size()) {
				((ItemStackHandler) inv).setStackInSlot(i, oldInv.get(i));
				oldInv.set(i, ItemStack.EMPTY);

		oldInv.forEach((s) -> ((PlayerEntity) entityIn).dropItem(s, true));

	super.inventoryTick(stack, worldIn, entityIn, itemSlot, isSelected);

public static int getSizeFromLevel(int level) {
	return 9 * (1 + level);

So I want to compare the enchantment level with the current inventory size in Item#inventoryTick and resize the inventory correctly when they don't match. However, whenever I open my backpack inventory, I only see 9 slots. (chat with slot: 9, size: the correct size) I thought that the cause is that the NBT is not updated, but I do not understand the hierarchical structure under ForgeCaps of the NBT in the item stack.

Do you think this is due to NBT? Also, if so, please tell me the structure of capabilities up to NBT.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...

Important Information

By using this site, you agree to our Privacy Policy.