OpenScreen.java

/* Entity Class

@Override
    protected InteractionResult mobInteract(Player player, InteractionHand hand) {
        if (!player.level.isClientSide() && hand.equals(InteractionHand.MAIN_HAND)) {

            ServerPlayer serverPlayer = (ServerPlayer) player;
            this.getCapability(NPCTradesProvider.NPC_TRADES).ifPresent(data -> {
                Networking.sendToPlayer(new OpenScreen(this.getId(), data.getTrades()), serverPlayer);
            });

        }
        return super.mobInteract(player, hand);
    }

*/

package com.fantalatone.npcmod.core.network.packet;

public class OpenScreen {

    public final int baseID;
    public final Map<ItemStack, ItemStack> baseTrades;
    public OpenScreen(int id, Map<ItemStack, ItemStack> trades) {
        System.out.println(trades);

        this.baseID = id;
        this.baseTrades = trades;
    }

    public OpenScreen(FriendlyByteBuf buf) {
        this(buf.readInt(), buf.readMap(FriendlyByteBuf::readItem, FriendlyByteBuf::readItem));
    }

    public void toBytes(FriendlyByteBuf buf) {
        buf.writeInt(this.baseID);
        buf.writeMap(this.baseTrades, FriendlyByteBuf::writeItem, (a, b) -> {
            System.out.println("A " + a);
            System.out.println("B " + b);
        });
    }

    public boolean handle(Supplier<NetworkEvent.Context> supplier) {
        NetworkEvent.Context context = supplier.get();
        context.enqueueWork(() -> {
            Entity entity = Minecraft.getInstance().level.getEntity(baseID);

            System.out.println("Hi From Packet!");

            if (entity instanceof NPCEntity npc) {
                Minecraft.getInstance().setScreen(new NPCScreen(npc, (HashMap<ItemStack, ItemStack>) this.baseTrades));
            }
        });
        context.setPacketHandled(true);
        return true;
    }
}