Here is my first attempt at using Capability and IItemHandler. The tile seems to work fine, but I would like someone's review to verify that I did this right or if something can be improved.

 

public class TileStrongChest extends GeneralTileEntity implements IItemHandlerModifiable
{
    final static public String CHESTTYPE="Chest type",ITEMSTACK="Item stack";
    public int type;
    ItemStack[] storage;
    static public Capability<IItemHandler> iItemHandler=CapabilityItemHandler.ITEM_HANDLER_CAPABILITY;
    public ItemStackHandler itemStackHandler;
    public TileStrongChest(){super();}
    public TileStrongChest(int metadata)
    {
        super();
        type=metadata;
        storage=new ItemStack[metadata==0 ? 54 : metadata==1 ? 81 : 108];
        itemStackHandler=new ItemStackHandler(storage);
    }

    @Override
    public boolean hasCapability(Capability<?> capability, EnumFacing facing)
    {
        if(capability==iItemHandler) return true;
        return super.hasCapability(capability, facing);
    }

    @Override
    public <T> T getCapability(Capability<T> capability, EnumFacing facing)
    {
        if(capability==iItemHandler) return (T) this;
        return super.getCapability(capability, facing);
    }

    @Nullable
    @Override
    public ITextComponent getDisplayName()
    {
        int stacks=0;
        for (int i = 0; i < getSlots(); i++)
        {
            if(storage[i]!=null)stacks++;
        }
        return new TextComponentString(stacks+"/"+ getSlots());
    }

  
    @Override
    public int getSlots()
    {
        return storage.length;
    }

   
    @Override
    public ItemStack getStackInSlot(int slot)
    {
        return storage[slot];
    }

  
    @Override
    public ItemStack insertItem(int slot, ItemStack stack, boolean simulate)
    {
        return itemStackHandler.insertItem(slot,stack,simulate);
    }

   
    @Override
    public ItemStack extractItem(int slot, int amount, boolean simulate)
    {

        return itemStackHandler.extractItem(slot,amount,simulate);
    }

    
    @Override
    public void setStackInSlot(int slot, ItemStack stack)
    {
        storage[slot]=stack;
    }

    @Override
    public NBTTagCompound writeToNBT(NBTTagCompound compound)
    {
        NBTTagCompound nbtTagCompound=super.writeToNBT(compound);
        int number=0;
        for(ItemStack itemStack: storage)
        {
            if(itemStack!=null)
            {

                NBTTagCompound item=itemStack.writeToNBT(new NBTTagCompound());
                compound.setTag(ITEMSTACK+number,item);
            }
            number++;
        }
        nbtTagCompound.setShort(CHESTTYPE, (short) type);
        return nbtTagCompound;
    }

    @Override
    public void readFromNBT(NBTTagCompound compound)
    {
        super.readFromNBT(compound);
        type=compound.getShort(CHESTTYPE);
        switch (type)
        {
            case 0: storage=new ItemStack[54];break;
            case 1: storage=new ItemStack[81];break;
            case 2: storage=new ItemStack[108];break;
        }
        for (int i = 0; i < storage.length; i++)
        {
            ItemStack itemStack=ItemStack.loadItemStackFromNBT(compound.getCompoundTag(ITEMSTACK+i));
            if(itemStack!=null)storage[i]=itemStack;
        }
        itemStackHandler=new ItemStackHandler(storage);
    }
}

The whole point of the Capability system is that you don't implement interfaces on your

TileEntity

, instead you store the objects in the

TileEntity

and override the

ICapabilityProvider

methods to return them. Forge's documentation explains this in more detail here. I also have a simple explanation here.

 

• Don't implement

  IItemHandler

  on your

  TileEntity

  .
  

• Either use the

  CapabilityItemHandler.ITEM_HANDLER_CAPABILITY

  field directly or annotate your own field with

  @CapabilityInject

  . Don't use the existing field to initialise your own.
  

• Don't store the

  ItemStack

  array, only interact with your inventory through the

  ItemStackHandler

  
  

• ItemStackHandler

  implements

  INBTSerializable

  , use this to write it to and read it from NBT
  

All right, I refactored it, now it looks like this:

public class TileStrongChest extends GeneralTileEntity
{
    final static public String CHESTTYPE = "Chest type", ITEMSTACKS = "Item stacks";
    public int type;

    public ItemStackHandler itemStackHandler;
    public TileStrongChest() {super();}

    public TileStrongChest(int metadata)
    {
        super();
        type = metadata;
        itemStackHandler=new ItemStackHandler(metadata==0 ? 54 : metadata==1 ? 81 : 108);
    }

    @Override
    public boolean hasCapability(Capability<?> capability, EnumFacing facing)
    {
        if (capability == CapabilityItemHandler.ITEM_HANDLER_CAPABILITY) return true;
        return super.hasCapability(capability, facing);
    }

    @Override
    public <T> T getCapability(Capability<T> capability, EnumFacing facing)
    {
        if (capability == CapabilityItemHandler.ITEM_HANDLER_CAPABILITY) return (T) itemStackHandler;
        return super.getCapability(capability, facing);
    }

    @Nullable
    @Override
    public ITextComponent getDisplayName()
    {
        int stacks=0;
        for (int i = 0; i < itemStackHandler.getSlots(); i++)
        {
            if(itemStackHandler.getStackInSlot(i)!=null)stacks++;
        }
        return new TextComponentString(stacks+"/"+ itemStackHandler.getSlots());
    }

    @Override
    public NBTTagCompound writeToNBT(NBTTagCompound compound)
    {
        NBTTagCompound nbtTagCompound=super.writeToNBT(compound);
        NBTTagCompound handlernbt= itemStackHandler.serializeNBT();
        nbtTagCompound.setTag(ITEMSTACKS,handlernbt);
        nbtTagCompound.setShort(CHESTTYPE, (short) type);
        return nbtTagCompound;
    }

    @Override
    public void readFromNBT(NBTTagCompound compound)
    {
        super.readFromNBT(compound);
        type=compound.getShort(CHESTTYPE);
        itemStackHandler=new ItemStackHandler();
        itemStackHandler.deserializeNBT(compound.getCompoundTag(ITEMSTACKS));
    }

}

 

Seems to be working.

Although I have read the docs few times, I didn't understand it right away. I assert that it needs to show an example, or a link to one.

That looks correct.

 

I believe LexManos is strongly against the Forge documentation containing any "copy-pasta" code, i.e. fully working code blocks with minimal explanation apart from "copy this code into your code to make it work". If you have some well-documented example code, it may be added (though I don't speak for the Forge team).

Thanks, plus to you.