Hi there,

 

I'm currently trying to code a new crafting table that has 2 additional slots for specific items. So I'm trying to prevent players from adding any item, other than the correct ones, to that slot.

 

To do this I have created a new SlotSolvent class that overrides the "isItemValid" check and will only return true if the itemstack being added is the same as one of the allowable items. However this does not seem to be  working. Can someone point out where I am going wrong?

 

SlotSolvent

public class SlotSolvent extends Slot {

    public SlotSolvent(IInventory inventory, int id, int xPos, int yPos) {
        super(inventory, id, xPos, yPos);
    }

    @Override
    public boolean isItemValid(ItemStack itemstack) {

        List<ItemStack> solvents = new ArrayList<>();

        // List of allowed solvents
        solvents.add(new ItemStack(ModItems.conicalFlask));

        for(ItemStack item: solvents)
        {
            if(item.getUnlocalizedName() == itemstack.getUnlocalizedName())
                return true;
        }
        return false;
    }
}

 

This is what I have in my container class

        this.addSlotToContainer(new SlotSolvent(te, 1, 19, 17));

(te is just my tile entity)

I'm not 100% but, isn't isItemValid only called when you try to input items with a hopper, for example on furnaces?

 

I think there are 2 methods, one used for player placing items and other for hoppers, but again, I'm not sure.

I'm not 100% but, isn't isItemValid only called when you try to input items with a hopper, for example on furnaces?

 

I think there are 2 methods, one used for player placing items and other for hoppers, but again, I'm not sure.

I'm pretty sure this is working, because once I added it I was unable to place items in said slot... I think my problem lies in checking whether the item being added is a valid item. I don't think my code in isItemValid is incorrect.

Nope, it's not. You are comparing Strings with '==' instead of #equals - google that for an explanation, but even more important is your implementation is, frankly, ridiculous.

 

You create a List, presumably of allowable items, and populate it every single time the method is called - don't do it that way, only create this list once and initialize it with a static block or some such.

 

Also, when comparing Items, you can compare the item directly, which is MUCH better than comparing strings:

for (ItemStack solvent : solvents) {
  if (itemstack.getItem() == solvent.getItem()) {
    return true;
  }
}

Note that if any of your solvent items have subtypes or use NBT to differentiate amongst themselves, you will need to make the logic more complex to account for that.

I would create a separate class to hold that last, too. Call it a recipe manager. It would then hold the relevant information about your custom recipes and you could have a method called isSolvent(item) which would check the passed stack/item against the list and return true or false.

Nope, it's not. You are comparing Strings with '==' instead of #equals - google that for an explanation, but even more important is your implementation is, frankly, ridiculous.

 

You create a List, presumably of allowable items, and populate it every single time the method is called - don't do it that way, only create this list once and initialize it with a static block or some such.

 

Also, when comparing Items, you can compare the item directly, which is MUCH better than comparing strings:

for (ItemStack solvent : solvents) {
  if (itemstack.getItem() == solvent.getItem()) {
    return true;
  }
}

Note that if any of your solvent items have subtypes or use NBT to differentiate amongst themselves, you will need to make the logic more complex to account for that.

Thanks, changing that worked. When I was coding it I absolutely knew that when I was creating the list it was probably done incorrectly.

I would create a separate class to hold that last, too. Call it a recipe manager. It would then hold the relevant information about your custom recipes and you could have a method called isSolvent(item) which would check the passed stack/item against the list and return true or false.

Yeah, probably should. Still trying to get the whole crafting system working though, one step at a time.