Vanilla Hoppers can exchange items with Entities if they implement IInventory. (Look at TileEntityHopper.getInventoryAtPosition)

The Forge Hook added in the Hopper tileentity is checking only for Blocks/TileEntitys with the ItemHandler Capability.

Although this isn't used in vanilla, as no Entities implement IInventory, Forge should stay compatible with Vanilla in this point, and should check for Entities with ItemHandler Capability, too.

Edited February 7, 20178 yr by Voidi

Could you explain a little? I don't quite understand what you are saying.

what he means is hoppers can extract items out of Entity's using the IInventory but not Itemhander

Spoiler

public static IInventory getInventoryAtPosition(World worldIn, double x, double y, double z)
    {
        IInventory iinventory = null;
        int i = MathHelper.floor_double(x);
        int j = MathHelper.floor_double(y);
        int k = MathHelper.floor_double(z);
        BlockPos blockpos = new BlockPos(i, j, k);
        Block block = worldIn.getBlockState(blockpos).getBlock();

        if (block.hasTileEntity())
        {
            TileEntity tileentity = worldIn.getTileEntity(blockpos);

            if (tileentity instanceof IInventory)
            {
                iinventory = (IInventory)tileentity;

                if (iinventory instanceof TileEntityChest && block instanceof BlockChest)
                {
                    iinventory = ((BlockChest)block).getContainer(worldIn, blockpos, true);
                }
            }
        }

        if (iinventory == null)
        {
            List<Entity> list = worldIn.getEntitiesInAABBexcluding((Entity)null, new AxisAlignedBB(x - 0.5D, y - 0.5D, z - 0.5D, x + 0.5D, y + 0.5D, z + 0.5D), EntitySelectors.HAS_INVENTORY);

            if (!list.isEmpty())
            {
                iinventory = (IInventory)list.get(worldIn.rand.nextInt(list.size()));
            }
        }

        return iinventory;
    }

 

as you can see in the spoiler getInventoryAtPosition first checks for tile and then for Entity's

it get also used in BlockDispenser line 54