Im attempting to use NBT Tags to save an array of block locations, matching with player names. I am trying to save this to my item. But it isn't working. I crash with this:

	public ItemStack onItemRightClick(ItemStack itemstack , World world, EntityPlayer player){
	itemstack = player.getCurrentEquippedItem();
	NBTTagCompound nbt = itemstack.getTagCompound();
	if(!world.isRemote)
	{
		if(player.isSneaking()){
			String i = nbt.getString("HELLO!");
			player.sendChatToPlayer(i);
		}else{
		nbt.setString("name", "YOLO");
		}
	}

	return itemstack;

}

(Also this is my first mod and also just a test to see if it will work). If there is a better way to save block location and player names. Please say! Also I need it to still contain this info even after restart. I am trying to make a protection mod and have everything working besides this! Please help if you can

You should have included some stacktrace to help us tackle your problem. But I'm guessing it's a NullPointerException you're getting, because in your code the NBTTagCompound nbt might be null, as well as String i. (They're null if they're not set on this itemStack.)

 

I think it's ok to save some data like block locations in your custom item in an NBT tag. You can set arrays, and all info should be retained on restart as well.

You should have included some stacktrace to help us tackle your problem. But I'm guessing it's a NullPointerException you're getting, because in your code the NBTTagCompound nbt might be null, as well as String i. (They're null if they're not set on this itemStack.)

 

I think it's ok to save some data like block locations in your custom item in an NBT tag. You can set arrays, and all info should be retained on restart as well.

Caused by: java.lang.NullPointerException

2013-01-16 19:15:49 [iNFO] [sTDERR] at bartboy8.needynecessities.common.ItemPortableItem.onItemRightClick(ItemPortableItem.java:35)

Line 35 is: nbt.setString("name", "YOLO");

 

Do u have any idea how I could set a variable to my itemStack?

I think it's done like this:

NBTTagCompound tag = itemStack.getTagCompound();
if (tag == null) {
tag = new NBTTagCompound();
itemStack.setTagCompound(tag);
}
tag.setString("playerName", player.getName());
tag.setInt("playerHP", player.getHP());

 

Methods getName() and getHP() are given just for example, they probably don't exist in player.

Also read this tutorial: www.minecraftforge.net/wiki/How_to_use_NBT_Tag_Compound