In my current endeavours to learn Forge Modding, I decided to code a simple backpack Item. nothing to special, just an item, that would act like a chest, and whenever used would open it's interface.

I had already done some test with Tile Entities and Containers, and I thought I could use a Container to do the job, and implement IContainerProvider in the Item. I had an ItemStackHandler in the BackpackItem class to hold the inventory but I ran into some problems when trying to store it in nbt, as in the Tile Entities they have their own methods I could override to deal with writing and reading nbt. So after some research I came accros Capabilities, I've been trying to understand them for some time now, but I cannot find any examples on how to use the IItemHandler to accomplish my goal.

I'd appreciate if someone could tell me how I should go about using capabilities to implement this simples backpack Item. Or just point me to a git repo that does something similiar.

EDIT: I have read the forge docs, they haven't helped much

 

EDIT 2: I read TheGreyGhost github repo on making an item that has an inventory and managed to accomplish it

the repo is: https://github.com/TheGreyGhost/MinecraftByExample/tree/master/src/main/java/minecraftbyexample/mbe32_inventory_item

Edited November 30, 20204 yr by kiou.23

2 hours ago, diesieben07 said:

You cannot just store it in your item class, because there is only one instance of that for all stacks of your item - they would all share the same inventory.

Yes, I am aware of this. It was when I realized this that I searched and found about Capabilities

2 hours ago, diesieben07 said:

To add capabilities to your item you need to override initCapabilities in your Item class. In there return a new instance of an ICapabilitySerializable implementation. This implementation exposes the capabilities of your item and also handles serialization to NBT.

So I need to create my own class that implements ICapabilitySerializable? and then I can have the ItemStackHandler stored in it?

 

EDIT: and then what? I do still need a Container and a ContainerScreen correct? how do I open the screen and pass the contents of the Capability to it? do I need to implement INamedContainerProvider on the capability class?

 

I'll share my code below

Edited November 29, 20204 yr by kiou.23

public class BackpackItem extends Item {

    public BackpackItem(Properties properties) {
        super(properties);
    }

    @Override
    public ActionResultType onItemUse(ItemUseContext context) {
        if (!context.getWorld().isRemote) {
            
        }

        return ActionResultType.SUCCESS;
    }

    @Override
    public ICapabilityProvider initCapabilities(ItemStack stack, CompoundNBT nbt) {
        return new BackpackCapability(this.getClass());
    }
}

 

public class BackpackCapability extends CapabilityProvider implements ICapabilitySerializable<CompoundNBT> {

    public BackpackCapability(Class baseClass) {
        super(baseClass);
    }

    private static final String INVENTORY_TAG = "inventory";

    ItemStackHandler inventory = new ItemStackHandler(27) {
        @Override
        public boolean isItemValid(int slot, ItemStack stack) {
            return !(stack.getItem() instanceof BackpackItem);
        }
    };

    @Override
    public LazyOptional<ItemStackHandler> getCapability(Capability cap, Direction side) {
        if (cap == CapabilityItemHandler.ITEM_HANDLER_CAPABILITY)
            return LazyOptional.of(() -> this.inventory);
        return super.getCapability(cap, side);
    }


    @Override
    public CompoundNBT serializeNBT() {

        CompoundNBT nbt = new CompoundNBT();
        nbt.put(INVENTORY_TAG, this.inventory.serializeNBT());

        return nbt;
    }

    @Override
    public void deserializeNBT(CompoundNBT nbt) {
        this.inventory.deserializeNBT(nbt);
    }
}