I am just starting to learn how to make GUIs and I have recently made one that has a 2x3 inventory at the top and a 2x1 inventory at the bottom, like the normal inventory just 2 wide. When I put anything in the top left slot it also appears in the bottom left slot and I don't understand why.

Post your container code

Here it is, I am using the one you gave me and I ma trying to adapt it.

 

 

package com.blocklings.entity;

import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.entity.player.InventoryPlayer;
import net.minecraft.inventory.Container;
import net.minecraft.inventory.IInventory;
import net.minecraft.inventory.Slot;
import net.minecraft.item.ItemStack;

public class ContainerBlockling extends Container {
protected IInventory gear;

private int player_inventory_x = 70;
private int player_inventory_y = 8;
private int loot_x = 8;
private int loot_y = 10;

public ContainerBlockling(InventoryPlayer inventoryPlayer, IInventory c) {
	gear = c;
	{
		int isize = c.getSizeInventory();
		for (int i = 0; i < 3; i++) {
			for (int j = 0; j < 2; j++) {
				addSlotToContainer(new Slot(c, j + i * 2, (loot_x + j * 18), (loot_y + i * 18)));
			}
		}
		for (int j = 0; j < 2; j++) {
			addSlotToContainer(new SlotUpgrade(c, j * 2, (loot_x + j * 18), (loot_y + j + 4 * 18)));
		}
	}
	bindPlayerInventory(inventoryPlayer);
}

public boolean canInteractWith(EntityPlayer player) {
	return gear.isUseableByPlayer(player);
}

protected void bindPlayerInventory(InventoryPlayer inventoryPlayer) {
	for (int i = 0; i < 3; i++) {
		for (int j = 0; j < 9; j++) {
			addSlotToContainer(new Slot(inventoryPlayer, j + i * 9 + 9, player_inventory_x + j * 18, player_inventory_y + i * 18));
		}
	}

	for (int i = 0; i < 9; i++) {
		addSlotToContainer(new Slot(inventoryPlayer, i, player_inventory_x + i * 18, player_inventory_y + 54 + 4));
	}
}

public ItemStack transferStackInSlot(EntityPlayer par1EntityPlayer, int par2) {
	ItemStack itemstack = null;
	Slot slot = (Slot) this.inventorySlots.get(par2);

	if (slot != null && slot.getHasStack()) {
		ItemStack itemstack1 = slot.getStack();
		itemstack = itemstack1.copy();

		int s = gear.getSizeInventory();

		if (par2 < s) {
			if (!this.mergeItemStack(itemstack1, s, this.inventorySlots.size(), true)) {
				return null;
			}
		} else if (!this.mergeItemStack(itemstack1, 0, s, false)) {
			return null;
		}

		if (itemstack1.stackSize == 0) {
			slot.putStack(null);
		} else {
			slot.onSlotChanged();
		}
	}

	return itemstack;
}

public void onContainerClosed(EntityPlayer par1EntityPlayer) {
	super.onContainerClosed(par1EntityPlayer);
	this.gear.closeInventory();
}
}

 

Slots in container numerated from 0 to inventory_size - 1

 

Let's look at your code.

 

for (int i = 0; i < 3; i++) {
for (int j = 0; j < 2; j++) {
  addSlotToContainer(new Slot(c, j + i * 2, (loot_x + j * 18), (loot_y + i * 18)));
}

 

This code adds slots: 0, 1, 2, 3, 4, 5

 

for (int j = 0; j < 2; j++) {
addSlotToContainer(new SlotUpgrade(c, j * 2, (loot_x + j * 18), (loot_y + j + 4 * 18)));
}

 

This code adds slots: 0 (again), and 5 (again)

 

I think you should edit second part to this:

for (int j = 0; j < 2; j++) {
addSlotToContainer(new SlotUpgrade(c, 6 + j, (loot_x + j * 18), (loot_y + j + 4 * 18)));
}

And it will add slots 6 and 7 instead of 0 and 5

Thanks for explaining it and showing me what to do. It makes a lot more sense now. Once last thing though, I want to check the item in a current slot so how would I go about that?

(IInventory variable).getStackInSlot(number) ?

Thanks, I believe I am all set now Can't thank you enough.