Hey! So, following:

I want to create backpacks that open when you right click with my custom item.

This is in my custom item class:

    @Nullable
    @Override
    public ICapabilityProvider initCapabilities(ItemStack stack, @Nullable CompoundTag nbt) {
        ItemStackHandler itemHandler = new ItemStackHandler(27);
        return ChestItemProvider.from(CapabilityItemHandler.ITEM_HANDLER_CAPABILITY, () -> itemHandler);
    }

This is my ChestItemProvider:

public class ChestItemProvider implements ICapabilityProvider {

    private final Capability<IItemHandler> capability;
    private final LazyOptional<IItemHandler> implementation;

    public ChestItemProvider(Capability<IItemHandler> capability, LazyOptional<IItemHandler> implementation) {
        this.capability = capability;
        this.implementation = implementation;
    }

    public static ChestItemProvider from(Capability<IItemHandler> cap, NonNullSupplier<IItemHandler> impl) {
        return new ChestItemProvider(cap, LazyOptional.of(impl));
    }

    @Nonnull
    @Override
    public <T> LazyOptional<T> getCapability(@Nonnull Capability<T> cap, @Nullable Direction side) {
        if (cap == CapabilityItemHandler.ITEM_HANDLER_CAPABILITY) {
            return implementation.cast();
        }
        return LazyOptional.empty();
    }
}

So, a few questions:

Is this implementation correct to this point?

How do I open a gui with IItemHandler and how do I save the changed contents?

This is what I have now:

    @SubscribeEvent
    public void onRightClick(PlayerInteractEvent.RightClickItem event) {
        if (!(event.getItemStack().is(this))) return;
        if (event.getSide() == LogicalSide.CLIENT) return;

        ItemStack item = event.getItemStack();
        ServerPlayer player = (ServerPlayer) event.getPlayer();
        LazyOptional<IItemHandler> cap = item.getCapability(CapabilityItemHandler.ITEM_HANDLER_CAPABILITY);
        if (cap.isPresent()) {
            NetworkHooks.openGui(((ServerPlayer) event.getPlayer()),
                    new SimpleMenuProvider((windowId, playerInventory, playerEntity) ->
                            ChestMenu.threeRows(1, new Inventory(player)), new TextComponent("Test")));
        }
    }

But this just opens a blank inventory, I could copy the IItemHandler's content to a new Inventory instance, but is this really the way you do it?

14 minutes ago, diesieben07 said:

Implement INBTSerializable on your ICapabilityProvider.

Can I use the ItemStackHandler's serialization like this?

public class ChestItemProvider implements ICapabilityProvider, INBTSerializable<CompoundTag> {

    private final Capability<IItemHandler> capability;
    private final LazyOptional<IItemHandler> implementation;

    public ChestItemProvider(Capability<IItemHandler> capability, LazyOptional<IItemHandler> implementation) {
        this.capability = capability;
        this.implementation = implementation;
    }

    public static ChestItemProvider from(Capability<IItemHandler> cap, NonNullSupplier<IItemHandler> impl) {
        return new ChestItemProvider(cap, LazyOptional.of(impl));
    }

    @Nonnull
    @Override
    public <T> LazyOptional<T> getCapability(@Nonnull Capability<T> cap, @Nullable Direction side) {
        if (cap == CapabilityItemHandler.ITEM_HANDLER_CAPABILITY) {
            return implementation.cast();
        }
        return LazyOptional.empty();
    }

    @Override
    public CompoundTag serializeNBT() {
        AtomicReference<CompoundTag> tag = new AtomicReference<>(new CompoundTag());
        implementation.resolve().ifPresent(itemHandler -> {
            tag.set(((ItemStackHandler) itemHandler).serializeNBT());
        });
        return tag.get();
    }

    @Override
    public void deserializeNBT(CompoundTag nbt) {
        implementation.resolve().ifPresent(itemHandler -> {
            ((ItemStackHandler) itemHandler).deserializeNBT(nbt);
        });
    }
}

 

36 minutes ago, diesieben07 said:

You need to create and register a custom MenuType and register it like any other registry entry. Use IForgeMenuType for this.

Like this?

public class ChestItemMenu implements IForgeMenuType<ChestMenu> {

    private static final MenuType<ChestMenu> CHEST_ITEM_MENU = register("chest_item_menu", ChestMenu::threeRows);

    private static <T extends AbstractContainerMenu> MenuType<T> register(String p_39989_, MenuType.MenuSupplier<T> p_39990_) {
        return Registry.register(Registry.MENU, p_39989_, new MenuType<>(p_39990_));
    }

    @Override
    public ChestMenu create(int windowId, Inventory playerInv, FriendlyByteBuf extraData) {
        return ChestMenu.threeRows(windowId, playerInv);
    }
}

 

    @SubscribeEvent
    public void onSetup(FMLClientSetupEvent event) {
        event.enqueueWork(() -> {
            MenuScreens.register(ChestItemMenu.CHEST_ITEM_MENU, ContainerScreen::new);
        });
    }

And this is how I register it. How can I open that GUI now?

Okay, so this is my code now:

public class CIContainer extends AbstractContainerMenu {

    public final IItemHandler handler;

    public static CIContainer fromNetwork(final int windowId, final Inventory playerInventory, FriendlyByteBuf data) {
        return new CIContainer(windowId, playerInventory, new ItemStackHandler(27));
    }

    public CIContainer(final int windowId, final Inventory playerInventory, IItemHandler handler) {
        super(BannedTools.CI_CONTAINER.get(), windowId);

        this.handler = handler;

        addPlayerSlots(playerInventory);
        addMySlots();
    }

    private void addPlayerSlots(Inventory playerInventory) {
        int originX = 7;
        int originY = 67;

        //Hotbar
        for (int col = 0; col < 9; col++) {
            int x = originX + col * 18;
            int y = originY + 58;
            this.addSlot(new Slot(playerInventory, col, x+1, y+1));
        }

        //Player Inventory
        for (int row = 0; row < 3; row++) {
            for (int col = 0; col < 9; col++) {
                int x = originX + col * 18;
                int y = originY + row * 18;
                int index = (col + row * 9) + 9;
                this.addSlot(new Slot(playerInventory, index, x+1, y+1));
            }
        }
    }

    private void addMySlots() {
        if (this.handler == null) return;

        int cols = 9;
        int rows = 3;

        int slot_index = 0;

        for (int row = 0; row < rows; row++) {
            for (int col = 0; col < cols; col++) {
                int x = 7 + col * 18;
                int y = 17 + row * 18;

                this.addSlot(new SlotItemHandler(this.handler, slot_index, x + 1, y + 1));
                slot_index++;
                if (slot_index >= 27)
                    break;
            }
        }

    }

    @Override
    public void clicked(int slot, int dragType, ClickType clickTypeIn, Player player) {
        getSlot(slot).container.setChanged();
        super.clicked(slot, dragType, clickTypeIn, player);
    }

    @Override
    public boolean stillValid(Player player) {
        return true;
    }

    @Override
    @Nonnull
    public ItemStack quickMoveStack(@Nonnull Player playerIn, int index) {
        ItemStack itemstack = ItemStack.EMPTY;
        Slot slot = this.slots.get(index);

        if (slot.hasItem()) {
            int bagslotcount = this.slots.size();
            ItemStack itemstack1 = slot.getItem();
            itemstack = itemstack1.copy();
            if (index < playerIn.getInventory().items.size()) {
                if (!this.moveItemStackTo(itemstack1, playerIn.getInventory().items.size(), bagslotcount, false))
                    return ItemStack.EMPTY;
            } else if (!this.moveItemStackTo(itemstack1, 0, playerIn.getInventory().items.size(), false)) {
                return ItemStack.EMPTY;
            }
            if (itemstack1.isEmpty()) slot.set(ItemStack.EMPTY); else slot.setChanged();
        }
        return itemstack;
    }
}

Registering:

    private static final DeferredRegister<MenuType<?>> CONTAINERS = DeferredRegister.create(ForgeRegistries.CONTAINERS, MODID);

    public static final RegistryObject<MenuType<CIContainer>> CI_CONTAINER = CONTAINERS.register("ci_container", () -> IForgeMenuType.create(CIContainer::fromNetwork));

And this is how I open the inventory:

    @SubscribeEvent
    public void onRightClick(PlayerInteractEvent.RightClickItem event) {
        if (!(event.getItemStack().is(this))) return;
        if (event.getSide() == LogicalSide.CLIENT) return;
        ItemStack item = event.getItemStack();
        ServerPlayer player = (ServerPlayer) event.getPlayer();
        LazyOptional<IItemHandler> cap = item.getCapability(CapabilityItemHandler.ITEM_HANDLER_CAPABILITY);
        if (cap.isPresent()) {
            IItemHandler itemHandler = cap.resolve().get();
            NetworkHooks.openGui(player,
                    new SimpleMenuProvider( (windowId, playerInventory, playerEntity) ->
                            new CIContainer(windowId, playerInventory, itemHandler), new TextComponent("Test")));
        }
    }

openGui() is executed, but nothing happens.

26 minutes ago, diesieben07 said:

Are you sure this worked correctly?

I figured it out, didn't register correctly. Thank you!