[1.18.2] Sync block inventory with item

[Daeruin]

I'm converting my old mod from 1.12 to 1.18. It's basically a backpack mod except it's wicker baskets. You can place them as a block or hold them as an item and view the inventory while holding it.

I have most everything working except the inventory doesn't sync between the block and the item. If I put something in the block inventory, then break the block, pick it up, and try to view the inventory from my hand, the basket is empty. And vice versa - if I put something in the basket inventory while holding it as an item, then place it as a block, the block inventory is empty. It seems the way I used to do it in 1.12 doesn't work anymore and I can't figure out what to do. I couldn't find any other backpack mods for 1.18 that actually use capabilities. Help would be much appreciated.

Full repo is here. Or some direct links:

• Basket Block
• Basket Block Entity
• Basket Block Item
• Capability Provider
• ItemStackHandler implementation
• Basket Menu

 

[ChampionAsh5357]

  On 1/23/2023 at 6:20 AM, Daeruin said:

If I put something in the block inventory, then break the block, pick it up, and try to view the inventory from my hand, the basket is empty.

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So, there are two methods. You could do something like the shulker box and write the capability data to the correct location to the item and then just write it back on placement. Or, you can override `spawnAfterBreak` to modify the itemstack with the capability data of the block entity and then just write to block within blockitem with the other update tag methods.

[Daeruin]

 

  On 1/23/2023 at 3:19 PM, ChampionAsh5357 said:

you can override `spawnAfterBreak` to modify the itemstack with the capability data of the block entity

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It tried this, but by the time spawnAfterBreak occurs, the BlockEntity has already been deleted, so I can't get the inventory from it. So I tried it in playerWillDestroy, and it appears as though the inventory is being saved to the ItemStack that's part of the ItemEntity that I'm spawning. Yet when the BlockItem's use method occurs, the item no longer seems to have a capability attached to it. I am supplying my capability provider during initCapabilities.

If I use BlockEntity#saveToItem during playerWillDestroy, the inventory data gets saved to a BlockEntityTag NBT, which persists all the way through breaking the block, picking it up, and placing it back down.

Block#playerWillDestroy:

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@Override
    public void playerWillDestroy(Level level, @NotNull BlockPos pos, @NotNull BlockState blockState, @NotNull Player player)
    {
        BlockEntity blockEntity = level.getBlockEntity(pos);

        if (blockEntity instanceof BasketBlockEntity && !level.isClientSide)
        {
            ItemStack newItemStack = new ItemStack(this);

            blockEntity.saveToItem(newItemStack); // Creates BlockEntityTag with inventory data - this persists
            BasketItemStackHandler blockInventory = ((BasketItemStackHandler) blockEntity.getCapability(CapabilityItemHandler.ITEM_HANDLER_CAPABILITY).orElseThrow(() -> new RuntimeException("NO CAPABILITY FOUND")));
            BasketItemStackHandler itemInventory = ((BasketItemStackHandler) newItemStack.getCapability(CapabilityItemHandler.ITEM_HANDLER_CAPABILITY).orElseThrow(() -> new RuntimeException("NO CAPABILITY FOUND")));
            CompoundTag inventoryTag = blockInventory.serializeNBT();

            itemInventory.deserializeNBT(inventoryTag); // Saves inventory to ItemStack capability tag - this does not persist

            ItemEntity itemEntity = new ItemEntity(level,
                    (double)pos.getX() + 0.5D, (double)pos.getY() + 0.5D, (double)pos.getZ() + 0.5D,
                    newItemStack);

            itemEntity.setDefaultPickUpDelay();
            level.addFreshEntity(itemEntity);
        }

        super.playerWillDestroy(level, pos, blockState, player);
    }

BlockItem#initCapabilities:

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@Nullable
    @Override
    public ICapabilityProvider initCapabilities(ItemStack itemStack, @Nullable CompoundTag nbt)
    {
        BasketBlock basketBlock = ((BasketBlock) this.getBlock());
        // ItemStack coming in has a BlockEntityTag that I saved to it in BasketBlock.playerWillDestroy
        // NBT coming in is an empty inventory capability: {Parent:{Items:[],Size:9}}
        return new BasketCapabilityProvider(basketBlock.basketSize);
    }

BlockItem#use:

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@Override
    public @NotNull InteractionResultHolder<ItemStack> use(@NotNull Level level, @NotNull Player player, @NotNull InteractionHand interactionHand)
    {
        if (!level.isClientSide())
        {
            ItemStack heldItem = player.getItemInHand(interactionHand);
            // At this point the item has the BlockEntity tag but not the capability tag
            if (heldItem.getCapability(CapabilityItemHandler.ITEM_HANDLER_CAPABILITY).isPresent())
            {
                NetworkHooks.openGui((ServerPlayer) player, this, friendlyByteBuf -> friendlyByteBuf.writeItem(heldItem));
            }
        }
        return super.use(level, player, interactionHand);
    }

 

 

[ChampionAsh5357]

  On 1/25/2023 at 3:30 AM, Daeruin said:

It tried this, but by the time spawnAfterBreak occurs, the BlockEntity has already been deleted

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That's strange. `#spawnAfterBreak` should be called before any states are set to properly drop the resources. Otherwise, things like the shulker box wouldn't work properly. Did you set a breakpoint to verify this?

[Daeruin]

The shulker box does it in playerWillDestroy. I just looked it up. Anyway that's kinda beside the point. As I mentioned in my previous post, I'm successfully saving the capability on the ItemStack when the block is broken (during playerWillDestroy), and it gets restored when I place the block again. I just can't find it when I'm holding the ItemStack and need to view the inventory.

[Daeruin]

I lied, the capability is not persisting. If I use the vanilla BlockEntity#saveToItem, then the inventory persists from breaking the block to placing it back down again. It's basically how the shulker box does it. But the capability disappears at some point after spawning the ItemEntity and picking it up in my inventory. It's baffling to me because I'm basically doing everything I used to do in 1.12.

[ChampionAsh5357]

  On 1/26/2023 at 3:24 AM, Daeruin said:

The shulker box does it in playerWillDestroy. I just looked it up.

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Interesting, but whatever. I could just be misunderstanding how the loot table drops work there.

  On 1/26/2023 at 6:01 AM, Daeruin said:

I lied, the capability is not persisting. If I use the vanilla BlockEntity#saveToItem, then the inventory persists from breaking the block to placing it back down again. It's basically how the shulker box does it. But the capability disappears at some point after spawning the ItemEntity and picking it up in my inventory.

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So, it's not that the inventory is disappearing. How a block entity stores data and how the capability stores data on an item stack are different. As such, you can't read the itemstack data for the inventory unless you move it to the capability. So essentially, you would need to write the capability data to that on the itemstack. Then, on place, write it back to the block entity since it won't be in the tag to do it automatically.

[Daeruin]

Well, I figured out the problem. Basically I was being a doofus and I had two copies of the inventory in my capability provider—one inside a LazyOptional, like I should have, and a second one not inside a LazyOptional. The second one was old code from before I understood how to use the LazyOptional. The second inventory was always empty for obvious reasons but I was still using it to serialize/deserialize.

So it's now working solely with a capability, and I'm not using BlockEntity#saveToItem at all. I'm writing the BlockEntity's capability data to the ItemStack in playerWillDestroy when the block is broken, and writing the ItemStack's capability data back to the BlockEntity in setPlacedBy when the block is placed.