[1.18.2] onContentsChanged

[Squander]

Overrides the onContentChanged method. When I put an item, it calls the apply method, but I would like to call remove when I take item out of the container, but I don't think onContentChanged will let me do that.

[Luis_ST]

Could you please provide a useful context? Which exact method are you talking about? Where is the method located?

Please post your code.

[Squander]

public class ItemStackHandlerMod extends ItemStackHandler {
    private Player player;

    public ItemStackHandlerMod(int size) {
        super(size);
    }

    public ItemStackHandlerMod(int size, Player player) {
        super(size);
        this.player = player;
    }

    @Override
    protected void onContentsChanged(int slot) {
        if(player != null){
            if(getStackInSlot(slot).getItem() instanceof BaseAmulet amulet){
                amulet.apply(player);
            }
        }
    }
}

public class HealthAmulet extends BaseAmulet {
    public static final UUID HEALTH = UUID.fromString("c2d8616a-c58a-4d99-aec9-faad03858302");

    public HealthAmulet(Properties pProperties) {
        super(pProperties);
    }

    @Override
    public void apply(Player player) {
        AttributeInstance instance = player.getAttribute(Attributes.MAX_HEALTH);
        instance.addPermanentModifier(new AttributeModifier(HEALTH, "Health Amulet", 5, AttributeModifier.Operation.ADDITION));
    }

    @Override
    public void remove(Player player) {
        AttributeInstance instance = player.getAttribute(Attributes.MAX_HEALTH);
        instance.removeModifier(HEALTH);
    }
}

 

6 hours ago, Luis_ST said:

Could you please provide a useful context? Which exact method are you talking about? Where is the method located?

Please post your code.

 

[Luis_ST]

ItemStackHandler#onContentsChanged is called whenever a Item is added (via #insertItem), a Item is removed (via #extractItem) or a Item is set (via #setStackInSlot).

You should be able to run code after the Item is removed, by checking in #onContentsChanged if the Slot is empty or if there is a other Item in it.

[Squander]

42 minutes ago, Luis_ST said:

ItemStackHandler#onContentsChanged is called whenever a Item is added (via #insertItem), a Item is removed (via #extractItem) or a Item is set (via #setStackInSlot).

You should be able to run code after the Item is removed, by checking in #onContentsChanged if the Slot is empty or if there is a other Item in it.

I don't think it will work. I want to do it in a similar way to the inventory when I put my boots on, the attributes from it are added to the player when I take them off they are removed.

[Luis_ST]

21 minutes ago, Squander said:

I don't think it will work.

Why did you think that, what did you tried to test if this would work or not?

[Squander]

I'm not sure if I did it right

if(player != null){
            if(getStackInSlot(slot).isEmpty()){
                ((BaseAmulet)getStackInSlot(slot).getItem()).remove(player);
            }

            if(getStackInSlot(slot).getItem() instanceof BaseAmulet amulet){
                amulet.apply(player);
            }
        }

 

[warjort]

Why doesn't something like this work?

WARNING: This code is not tested, it just shows the idea. And see the comment in the code.

    @Override
    public void setStackInSlot(int slot, @NotNull ItemStack stack) {
        ItemStack previous = getStackInSlot(slot);
        super.setStackInSlot(slot, stack);
        // Probably needs some check here to see if "previous" and "stack" are the same item? 
        // i.e. item swap of two different amulets
        onRemoved(previous);
    }

    @Override
    public @NotNull ItemStack extractItem(int slot, int amount, boolean simulate) {
        ItemStack extracted = super.extractItem(slot, amount, simulate);
        if (!simulate) {
            onRemoved(extracted);
        }
        return extracted;
    }

    protected void onRemoved(ItemStack itemStack) {
        // Your code here
    }

 

[warjort]

Note: That code above only works if the item stacks are always amount=1 like armor or tools.

It doesn't take into account removing part of stacked items.

[Squander]

1 hour ago, warjort said:

Note: That code above only works if the item stacks are always amount=1 like armor or tools.

It doesn't take into account removing part of stacked items.

Ok it works, but i don't know how i can prevent amulet of the same kind from being added to a container

[warjort]

Quote

Ok it works, but i don't know how i can prevent amulet of the same kind from being added to a container

One way would be to check if the stacks are the same (same item). Then skip the onRemove() call.

You might want a different check if you have custom nbt or something that means just checking the item is not enough.

if (!previous.isSame(itemStack)) {
    onRemoved(previous);
}

 

Edited August 25, 2022 by warjort

[Squander]

50 minutes ago, warjort said:

One way would be to check if the stacks are the same (same item). Then skip the onRemove() call.

You might want a different check if you have custom nbt or something that means just checking the item is not enough.

if (!previous.isSame(itemStack)) {
    onRemoved(previous);
}

 

i did something like this and it works too.

@Override
    public boolean isItemValid(int slot, @NotNull ItemStack stack) {
        for (int i = 0; i < getSlots(); i++) {
            ItemStack stack1 = getStackInSlot(i);
            if(stack.getItem() == stack1.getItem()){
                return false;
            }
        }
        return super.isItemValid(slot, stack);
    }