Attach an invisible, arbitrary piece of data to an ItemStack

I want to tag certain items to prevent them from being used. I know how to prevent them from being used, but it's the tag i'm having trouble with. I've been using the lore to store info up until now, and it works fine, but the tag is visible and kind of ugly. I want something completely invisible, like entity metadata.

Edit: I summon.. the Great, the Powerful, the Almighty xTrollxDudex ! Please help me, I'm not sure many others on this forum could give a proper answer.

 

Maurdekye
This? https://forums.bukkit.org/threads/hidden-lore-attributes.219156/

And also HURTFUL!

 

mattrick Well, if I were to use the first suggested method in that forum, a blank line would still show. And that's practically the same as what I have now. But the second method (suggested in the last post) seems relatively plausible, except for the fact I have no idea how to implement it.

 

Maurdekye
Nbt was what I was thinking as well, let me see if I can take a whack at it:

PHP:

private static final String CONSTANT_MOD_VAR = "CanPlaceOn";

public void tagItem(ItemStack item) {
    NBTTagCompound tag = CraftItemStack.asNMSCopy(item).getTag();
    NBTTagList canPlaceOn = new NBTTagList();

    if(tag.hasKey(CONSTANT_MOD_VAR)) {
        canPlaceOn = tag.getList(CONSTANT_MOD_VAR);
    }

    canPlaceOn.add(new NBTTagString("Tagged"));
}

public boolean canUse(ItemStack item) {
    NBTTagCompound tag = CraftItemStack.asNMSCopy(item).getTag();
    NBTTagList canPlaceOn = new NBTTagList();

    if(tag.hasKey(CONSTANT_MOD_VAR)) {
        canPlaceOn = tag.getList(CONSTANT_MOD_VAR);
    } else {
        return false;
    }

    if(canPlaceOn.size() < 1) {
        return false;
    }

    boolean exists = false;
    for(int i = 0; i <= canPlaceOn.size() - 1; i++) {
        if(canPlaceOn.get(i).equals(new NBTTagString("Tagged"))
            exists = true;
    }

    return exists;
}

 

xTrollxDudex Ah, thank you! I knew there were a couple kinks in that summoning spell I had to work out.

Edit: tag.getList() requires a String AND an int. What should that int be?

xTrollxDudex Extra tahg, for good measure.

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

Maurdekye
Crap. Use the get method instead, you will need to cast to NBTTagList after using it though.

 

Code:

    public NBTTagList getList(String s, int i) {
        try {   
            if (this.b(s) != 9) {   
              return new NBTTagList(); 
      } else {     
      NBTTagList nbttaglist = (NBTTagList) this.map.get(s);
              return nbttaglist.size() > 0 && nbttaglist.d() != i ? new NBTTagList() : nbttaglist;
            }
        } catch (ClassCastException classcastexception) {
          throw new ReportedException(this.a(s, 9, classcastexception));
        }
    }

Thats the code for getList. Seems like its checking if it is over 6, then, it calls more methods and creates a new one, I think. Hmmmm, confusion

 

xTrollxDudex The variable tag is returning null. Do I have to create the item's NBTTag?

 

Maurdekye
You shouldn't, the only way for it to return null is for the ItemStack to be null

 

calebbfmv Well, i've done checks, and none of the items i'm calling it on are null, even if their NBTTagCompound is null.

 

Maurdekye
Then you should just create a new NBTTagList, add a tag to it, and set it to CanPlaceOn tag.

 

xTrollxDudex Eh, how?

 

Maurdekye

PHP:

NBTTagList list = new NBtTagList();
list.add(new NBTTagString("Tagged"));

tag.set("CanPlaceOn", list);

 

xTrollxDudex I've replaced my method with this;

Code:java

public ItemStack makeVital(ItemStack item) {
    System.out.println(item.getType().name());
    CraftItemStack.asNMSCopy(item).setTag(new NBTTagCompound());
    NBTTagCompound tag = CraftItemStack.asNMSCopy(item).getTag();
    NBTTagList list = new NBTTagList();
    list.add(new NBTTagString("Vital"));
    tag.set("CanPlaceOn", list);
    return item;
}

And i'm getting an NPE on line 7. I'm fairly sure I didn't implement it correctly though.

 

Maurdekye
Or create a new NBTTagCompound on its own and add a list, then set tag? The only reason it could NPE is if the list is null or the tag is null. Set only adds the NBTBase to a HashMap in NBTTagCompound...

 

xTrollxDudex I don't understand what you're talking about, and the tag is the null object; I checked. Is there a specific piece of code you can give me that doesn't throw NPE's ?

 

Maurdekye
I haven't worked with NBT too often in the past, not sure now.

PHP:

NBTTagCompound tag = new NBTTagCompound();
NBTTagList list = new NBTTagList();
list.add(new NBTTagString("Vital"));
tag.set("CanPlaceOn", list);
CraftItemStack.asNMSCopy(item).setTag(tag);

 

xTrollxDudex Sorry for asking, but do you think you could repost new versions of your canUse and tagItem methods?

 

https://forums.bukkit.org/threads/s...tently-on-item-itemstack.174080/#post-1875531
https://github.com/aadnk/AttributeS...com/comphenix/attribute/AttributeStorage.java
Take a look at this