Sync container inventory

Hello. I have a custom inventory GUI that includes a special slot for a container item. The GUI also has a couple of slots that I would like to have synced with the contents of the container item, so that the player can place or remove items from the container without changing GUI's.

The contents of the container item can already be accessed by placing it into the hotbar, and right-clicking with it in hand, but that would mean needing to remove it from it's special slot first, essentially "equipping" it.

Does anybody have any suggestions?

Super easy

As long as you've set up your read/write NBT functions (inventory persists across a save/load boundary) then all you need is this:

        public Packet getDescriptionPacket() {
                NBTTagCompound nbtTag = new NBTTagCompound();
                this.writeToNBT(nbtTag);
                return new Packet132TileEntityData(this.xCoord, this.yCoord, this.zCoord, 1, nbtTag);
        }

        public void onDataPacket(INetworkManager net, Packet132TileEntityData packet) {
                readFromNBT(packet.data);
        }

How does that help keeping the slots in sync?

If your container Item is kept in sync when using it from the equipped slot, then it should be as simple as using that exact same method for when it's accessed from the custom slot.

For example, if you are using the Item's onUpdate method to save the inventory contents, it is not called automatically for custom slots, only vanilla inventory slots.

Use Forge's LivingUpdateEvent to check if the entity/player has your custom inventory slot and, if so, get the stack from there and call the onUpdate method for the item.

If you don't have your container Item inventory saved and synchronized even just when right-clicked, then you need to go back and get that part working first.

Well, I seem to have it mostly working now, but there is still one problem I am having.

I have a full container item, and an empty one. I can take one out of the "equip" slot, and place the other in, and the "contents" slots work as expected.

But if I were to directly swap containers by clicking on the occupied slot with the other container, the GUI doesn't update with the change of contents.

Through various tests, I have checked that the inventory slots themselves update, but not the GUI, and any interactions with "contents" slots can result in copying the contents of one container to the other.

Closing and re-opening the GUI does update properly, though. Suggestions?

After your code that updates the slot contents make a call to detectAndSendChanges()  in your container, that should make it work.