Please Help! How would I use NBT on a Item to store a randomly generated number? I look at the tutorial for NBT Tags, but there is not the same functions used in a Item class? Is this possible?

 

THANKS TO HYDROFLAME!!!

the nbt is not stored in the Item class but in a variable contained by the ItemStack

 

most function that Item has will give you a ItemStack as argument

 

aka (name may vary because i dont remember by heart)

 

public void onItemRightClick(ItemStack itemStack, and a bunch of other argument){
//here you can use the information about the itemstack nbt
//ex:
int theRandom = itemStack.stackTagCompound.getInteger("myRandomNumber");
	if(theRandom == 0){
		//here we DONT have anythin on the stack compound
		itemStack.stackTagCompound.setInteger("myRandomNumber", (int)(Math.random()*100));//generate a number between 0-100 and place it on the nbt
	}else{
		System.out.println("the number of thsi item is: "+theRandom);
	}
}

Wow! Thank you so much!!! I really thought there was no way of doing it I soo happy! +1 Thank You!

Right when i get excited i get a error 

 

here is the error:

 

 

 2013-08-07 13:33:45 [iNFO] [sTDOUT] java.lang.NullPointerException
2013-08-07 13:33:45 [iNFO] [sTDOUT] 	at com.gmod622.SickMod.item.LicenseItemClass.onItemRightClick(LicenseItemClass.java:23)
2013-08-07 13:33:45 [iNFO] [sTDOUT] 	at net.minecraft.item.ItemStack.useItemRightClick(ItemStack.java:176)
2013-08-07 13:33:45 [iNFO] [sTDOUT] 	at net.minecraft.client.multiplayer.PlayerControllerMP.sendUseItem(PlayerControllerMP.java:428)
2013-08-07 13:33:45 [iNFO] [sTDOUT] 	at net.minecraft.client.Minecraft.clickMouse(Minecraft.java:1405)
2013-08-07 13:33:45 [iNFO] [sTDOUT] 	at net.minecraft.client.Minecraft.runTick(Minecraft.java:1854)
2013-08-07 13:33:45 [iNFO] [sTDOUT] 	at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:898)
2013-08-07 13:33:45 [iNFO] [sTDOUT] 	at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:826)
2013-08-07 13:33:45 [iNFO] [sTDOUT] 	at net.minecraft.client.main.Main.main(Main.java:93)
2013-08-07 13:33:45 [iNFO] [sTDOUT] 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
2013-08-07 13:33:45 [iNFO] [sTDOUT] 	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
2013-08-07 13:33:45 [iNFO] [sTDOUT] 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
2013-08-07 13:33:45 [iNFO] [sTDOUT] 	at java.lang.reflect.Method.invoke(Unknown Source)
2013-08-07 13:33:45 [iNFO] [sTDOUT] 	at net.minecraft.launchwrapper.Launch.launch(Launch.java:57)
2013-08-07 13:33:45 [iNFO] [sTDOUT] 	at net.minecraft.launchwrapper.Launch.main(Launch.java:18)
2013-08-07 13:33:45 [iNFO] [sTDOUT] 

 

 

here is my code:

 

Item:

 

 

 
import com.gmod622.SickMod.tile.TileEntityLicense;

import net.minecraft.creativetab.CreativeTabs;
import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.item.Item;
import net.minecraft.item.ItemStack;
import net.minecraft.tileentity.TileEntity;
import net.minecraft.world.World;

public class LicenseItemClass extends Item {

public LicenseItemClass(int par1) {
	super(par1);
	this.setCreativeTab(CreativeTabs.tabMaterials);
}


 public ItemStack onItemRightClick(ItemStack par1ItemStack, World par2World, EntityPlayer par3EntityPlayer) {
	//here you can use the information about the itemstack nbt
	//ex:
	int theRandom = par1ItemStack.stackTagCompound.getInteger("myRandomNumber");
			if(theRandom == 0){
				//here we DONT have anythin on the stack compound
				par1ItemStack.stackTagCompound.setInteger("myRandomNumber", (int)(Math.random()*100));//generate a number between 0-100 and place it on the nbt
			}else{
				System.out.println("the number of thsi item is: "+theRandom);
			}
			return par1ItemStack;
	}


}

 

 

 

Please help me

if you dont knwo what :

java.lang.NullPointerException mean, i suggest you google that

 

but you need to make a null check before using the stackTagCompound and create it if its null

To create a TagCompound.

NBTTagCompound tag = new NBTTagCompound();
tag.setTagCompound("tagName", new NBTTagCompound());
tag.getTagCompound("tagName").setInteger("YourInteger");
ItemStack.setTagCompound(tag);

 

To Read An tagCompound

NBTTagCompound tag = ItemStack.getTagCompound("tagName");
int i = tag.getInteger("YourInteger");

 

Thats it!

@Moritz, you realise you're creating a tagcompound inside a tagcompound right?

that exactly like using hashmap to store hashmaps

This is probably a newbie question but, I really don't know how to check if something is null. I know your probably not gonna answer this but, worth a shot... I haven't been code for about 1 1/2 now, so i really don't know stuff i didn't get indepth with it.

then you should really learn a bit more java (either while you continue to make your mod or wtv) because itll help you a LOT

 

but a null check is like this:

Object a;

//more code

if(a == null){

//do or dont do something depending on the logic

}

  What do i put for the object? because if i make it the randomNumber then it gives me a error say your need to create it. So am i supposed to put something else? I probably sound like a noob.  :-[

I probably sound like a noob.

you do , but dont worry we know a lot of people prefer to learn+mod at the same time so they often arrive in problem like this

but basicly everything in java (except primitive type: int, float, double, byte, long, boolean) is child of Object. Whenever you do "new Soemthing()" you are creating an object that is a child of the class Object (yup confusing i know)

but a == null can be done with anything !

 

Item s = wtv;
if (s == null){
//hello
}

Block b = some other stuff;

if (b == null){
//hello again 
}

 

now in the specific case you have, you want to check if the stackTagCompound is null , if it is you want to create it

 

if(itemStack.stackTagCompound == null){
//here we know the nbt is null
itemStack.stackTagCompoung = new NBTTagCompound();
}
//and here we can continue to use it becasue we know that if it was null it was also created

 

Thank you so much, I wish I could give you 100 thank yous!

 

Every time I ask somthing i dont know they usally quit helping  But you sir are AWESOME, + Thank you and Credits