I want to make sure you can only put one type of any item in my custom inventory. I know i need to use the isItemValid method but I don't know how to check if that item already exists in my inventory.

Your post title and what you said in the description do not match.

Do you want to restrict your custom inventory slots to be able to hold just one type of item, or you want to check if an item is part of a inventory.

Your post title and what you said in the description do not match.

Do you want to restrict your custom inventory slots to be able to hold just one type of item, or you want to check if an item is part of a inventory.

I want to make sure not more than one type of item can be placed in the inventory.

 

Loop all other slots and check if the Item is already there.

Probably not like this because this crashes?

@Override
public boolean isItemValid(ItemStack itemstack) {
if (itemstack.getItem() instanceof IBauble ){
	for (int a = 0; a < inventory.INV_SIZE; a++) {
		if(itemstack.getIsItemStackEqual(inventory.getStackInSlot(a))){
			return true;
		}
	}
	return false;
}
	return false;
}

I guess it is crashign with an NullPointerException? You are never checking if the item stacks are null

Does itemstack has a method called "getIsItemStackEqual" ?

It probably does not. I doubt minecraft would use such ridiculous naming for their methods.

 

EDIT: Apparentely there is. Never used this before. My bad.

Does itemstack has a method called "getIsItemStackEqual" ?

It probably does not. I doubt minecraft would use such ridiculous naming for their methods.

 

From ItemStack Class

  @SideOnly(Side.CLIENT)
    public boolean getIsItemStackEqual(ItemStack p_179549_1_)
    {
        return this.isItemStackEqual(p_179549_1_);
    }

  private boolean isItemStackEqual(ItemStack other)
    {
        return this.stackSize != other.stackSize ? false : (this.item != other.item ? false : (this.itemDamage != other.itemDamage ? false : (this.stackTagCompound == null && other.stackTagCompound != null ? false : this.stackTagCompound == null || this.stackTagCompound.equals(other.stackTagCompound))));
    }

 

 

 

I guess it is crashign with an NullPointerException? You are never checking if the item stacks are null

Nope

http://pastebin.com/HkrTfcia

ItemStack#getIsItemStackEqual

is client-only, using it in common code will crash the dedicated server.

 

If you only care about the

Item

, use

ItemStack#getItem

and compare the

Item

s directly. If you care about the

Item

and metadata, use

ItemStack.areItemsEqual

. If you care about the

Item

, metadata and NBT, use

ItemStack.areItemStacksEqual

.

 

 

I guess it is crashign with an NullPointerException? You are never checking if the item stacks are null

Nope

http://pastebin.com/HkrTfcia

 

That is a

NullPointerException

.

@Override
public boolean isItemValid(ItemStack itemstack) {
if (itemstack.getItem() instanceof IBauble ){
	for (int a = 0; a < inventory.INV_SIZE; a++) {
		if(itemstack.areItemStacksEqual(itemstack, inventory.getStackInSlot(a))){
			if(inventory.getStackInSlot(a) != null){
				return true;
			}

		}
	}

}
	return false;
}

 

Thanks. Except now I cant put an item in the inventory at all.

You're returning

true

(item is valid for slot) when there's already an item of that type in the inventory and

false

(item isn't valid for slot) when there isn't.