[1.7.10] ItemStack saving question

[TheTrueForce]

Hi,

 

I've made a TileEntity (for a machine), and I want to save the inventory and energy that are currently stored in the machine.

I have 4 inventory slots, 3 inputs, and 1 output, and a EnergyStorage object from CoFHCore.

I'm using this code to try and save all this:

private EnergyStorage Storage;

// slots 0-2 are the inputs, slot 3 is the output
private ItemStack[] inventory;

@Override
public void readFromNBT(NBTTagCompound nbt) {
	this.Storage.readFromNBT(nbt);
	this.inventory[0] = ItemStack.loadItemStackFromNBT(nbt);
	this.inventory[1] = ItemStack.loadItemStackFromNBT(nbt);
	this.inventory[2] = ItemStack.loadItemStackFromNBT(nbt);
	this.inventory[3] = ItemStack.loadItemStackFromNBT(nbt);
	super.readFromNBT(nbt);
}

@Override
public void writeToNBT(NBTTagCompound nbt) {
	// TODO: Figure out why the inventory isn't saving, and fix it.
	nbt = Storage.writeToNBT(nbt);
	nbt = inventory[0].writeToNBT(nbt);
	nbt = inventory[1].writeToNBT(nbt);
	nbt = inventory[2].writeToNBT(nbt);
	nbt = inventory[3].writeToNBT(nbt);
	super.writeToNBT(nbt);
}

The ItemStack array is initialized in the constructor with 4 elements.

 

This isn't saving the TE, and it's throwing a nullPointerException on line 108 (the one with "inventory[3].writeToNBT()"), because that slot is currently null (empty).

 

This is the error stacktrace:

[09:11:43] [server thread/ERROR] [FML]: A TileEntity type com.trueForce.mclTweaks.tileentity.TECompressor has throw an exception trying to write state. It will not persist. Report this to the mod author
java.lang.NullPointerException
at com.trueForce.mclTweaks.tileentity.TECompressor.writeToNBT(TECompressor.java:108) ~[TECompressor.class:?]
at net.minecraft.world.chunk.storage.AnvilChunkLoader.writeChunkToNBT(AnvilChunkLoader.java:395) [AnvilChunkLoader.class:?]
at net.minecraft.world.chunk.storage.AnvilChunkLoader.saveChunk(AnvilChunkLoader.java:204) [AnvilChunkLoader.class:?]
at net.minecraft.world.gen.ChunkProviderServer.safeSaveChunk(ChunkProviderServer.java:287) [ChunkProviderServer.class:?]
at net.minecraft.world.gen.ChunkProviderServer.saveChunks(ChunkProviderServer.java:340) [ChunkProviderServer.class:?]
at net.minecraft.world.WorldServer.saveAllChunks(WorldServer.java:863) [WorldServer.class:?]
at net.minecraft.server.MinecraftServer.saveAllWorlds(MinecraftServer.java:370) [MinecraftServer.class:?]
at net.minecraft.server.integrated.IntegratedServer.tick(IntegratedServer.java:113) [integratedServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:485) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:752) [MinecraftServer$2.class:?]

 

I suspect that my use of null to denote an empty ItemStack (that is, one that does not contain any items) is wrong.

Am I correct in this suspicion, and what is the correct way to do so?

And also, am I doing anything else wrong?

[Choonster]

You're writing every

ItemStack

to the same compound tag, so each slot is overwriting the previous one. You need to write a list tag containing a compound tag for each slot's

ItemStack

. Include the slot number in each compound tag, skip any slots with a

null

ItemStack

.

 

Look at how

TileEntityChest

saves and loads its contents.

[nexusrightsi]

this is what i use for reading the inv nbt data

if (tagCompound.hasKey("Items"))
	{
		NBTTagList tagList = (NBTTagList) tagCompound.getTag("Items");
		this.inv = new ItemStack[4];

		for (int i = 0; i < tagList.tagCount(); ++i)
		{
			NBTTagCompound nbt = (NBTTagCompound) tagList.getCompoundTagAt(i);
			byte s = nbt.getByte("Slot");

			if (s >= 0 && s < this.inv.length)
			{
				this.inv[s] = ItemStack.loadItemStackFromNBT(nbt);
			}
		}
	}

 

and this is what i use for saving the inv data

NBTTagList tagList = new NBTTagList();
	for (int i = 0; i < this.inv.length; ++i)
	{
		if (this.inv[i] != null)
		{
			NBTTagCompound nbt = new NBTTagCompound();
			nbt.setByte("Slot", (byte) i);
			this.inv[i].writeToNBT(nbt);
			tagList.appendTag(nbt);
		}
	}
	tagCompound.setTag("Items", tagList);

[shadowfacts]

Are you ever initializing the

inventory

array?

[TheTrueForce]

Choonster:

Thanks for that, I hadn't realized that was happening. I would've looked at how some MC TileEntity saved, but the decompiled code is hideously hard to read.

Also, the energy isn't saving. I'm using the writeToNBT() method that comes with EnergyStorage. Should I tag that with a slot number, or put it in a nested NBTTagCompound?

 

nexusrightsi:

Thanks for that code.

I think I understand how that works, so I'll try to write my own methods before just copy/pasting those ones.

 

shadowfacts:

Yes. I am initializing inventory[] with this line in the constructor:

inventory[] = new ItemStack[this.getSizeInventory()];

The getSizeInventory() method just returns 4, from a private constant.

 

 

EDIT: OK, I've altered the load/save code to:

@Override
public void readFromNBT(NBTTagCompound nbt) {
	System.out.println("Beginning Load");
	this.inventory = new ItemStack[iNV_SIZE];
	NBTTagList invTags = (NBTTagList) nbt.getTag("inventory");
	NBTTagCompound swapTag = new NBTTagCompound(); 
	byte slotNum = 0;
	for (byte i = 0; i>=INV_SIZE; i++) {
		swapTag = invTags.getCompoundTagAt(i);
		slotNum = swapTag.getByte("slot");
		if (slotNum >=0 && slotNum <= INV_SIZE);
		inventory[slotNum] = ItemStack.loadItemStackFromNBT(swapTag);
		System.out.println("loaded slot " + slotNum + " : " + swapTag);
	}
	this.Storage.readFromNBT(nbt);
	super.readFromNBT(nbt);
}

@Override
public void writeToNBT(NBTTagCompound nbt) {
	System.out.println("Beginning Save");
	// TODO: Figure out why the inventory isn't saving, and fix it.
	NBTTagList invTags = new NBTTagList();
	NBTTagCompound swapTag = new NBTTagCompound();
	for (byte i=0; i >= INV_SIZE; i++) {
		swapTag = new NBTTagCompound();
		swapTag.setByte("slot", i);
		inventory[i].writeToNBT(swapTag);
		invTags.appendTag(swapTag);
		System.out.println("saved slot " + i + " : " + swapTag);
	}
	Storage.writeToNBT(nbt);
	nbt.setTag("inventory", invTags);
	super.writeToNBT(nbt);
}

This no longer throws an NPE, but the "tells" in these routines aren't showing up in the console. This leads me to believe that the NBT read/write methods aren't being called, for some reason. What would cause that?

I can pastebin the entire class if it'll help.

[Choonster]

Choonster:

Thanks for that, I hadn't realized that was happening. I would've looked at how some MC TileEntity saved, but the decompiled code is hideously hard to read.

Also, the energy isn't saving. I'm using the writeToNBT() method that comes with EnergyStorage. Should I tag that with a slot number, or put it in a nested NBTTagCompound?

 

It should be okay to save the

EnergyStorage

in the root compound tag or a nested compound tag. It's not a slot, it doesn't need a slot number.

[ovikk]

Try getting the NBTTagList by doing:

NBTTagList list = nbt.getTagList("inventory", NBT.TAG_COMPOUND);

 

Just a thought...

 

Also, you're functions are not called when you enter the chunk?

If so, have you registered your TileEntity?

Then, place a breakpoint in the NBT functions, and debug it.

[TheTrueForce]

Thanks, Ovikk, for pointing me to the breakpoints, and for that snippet of code.

It turns out that the methods were being called, but my loop condition was faulty and then the code NPE'd at a null ItemStack, so I put in a skipper. This is the working code:

@Override
public void readFromNBT(NBTTagCompound nbt) {
	//System.out.println("Beginning Load");
	this.inventory = new ItemStack[4];
	NBTTagList invTags = nbt.getTagList("inventory", NBT.TAG_COMPOUND);
	NBTTagCompound swapTag = new NBTTagCompound(); 
	byte slotNum = 0;
	for (byte i = 0; i <= 3; i++) {
		swapTag = invTags.getCompoundTagAt(i);
		slotNum = swapTag.getByte("slot");
		if (slotNum >=0 && slotNum <= 3);
		inventory[slotNum] = ItemStack.loadItemStackFromNBT(swapTag);
		//System.out.println("loaded slot " + slotNum + " : " + swapTag);
	}
	this.Storage.readFromNBT(nbt);
	super.readFromNBT(nbt);
}

@Override
public void writeToNBT(NBTTagCompound nbt) {
	//System.out.println("Beginning Save");
	NBTTagList invTags = new NBTTagList();
	NBTTagCompound swapTag = new NBTTagCompound();
	boolean check = false;
	for (byte i=0; i <= 3; i++) {
		swapTag = new NBTTagCompound();
		swapTag.setByte("slot", i);
		check = (inventory[i] != null);
		if (check) {
			inventory[i].writeToNBT(swapTag);
		}
		invTags.appendTag(swapTag);
		//System.out.println("saved slot " + i + " : " + swapTag);
	}
	Storage.writeToNBT(nbt);
	nbt.setTag("inventory", invTags);
	super.writeToNBT(nbt);
}

Thanks for your help. Now I need to make it actually process stuff, now that there's a point to doing so.

[ovikk]

Look in the TileEntityFurnace if you're stuck at how to process stuff. It's where I learned how to do it.