While trying to make some kind of "crafting table" by checking the items in the slots I seem to get a crash when i try to remove an item from any slot in the Tile Entity (Inventory slots work fine)

 

Here is what the GUI looks like:

http://prntscr.com/6rh5df

 

I get a NPE at the line

for(int i = 0; i < inventory.length; i++)

In the Tile entity -> public void writeToNBT(NBTTagCompound nbt)

 

[spoiler=Container]

public class ContainerSummoningTable extends Container {

public IInventory tableInventory;
private World world;

public ContainerSummoningTable(InventoryPlayer inventory, TileEntitySummoningTable entity, World w) {
	world = w;
	tableInventory = entity;
	this.addSlotToContainer(new Slot(entity, 0, 44, 17));
	this.addSlotToContainer(new Slot(entity, 1, 44, 35));
	this.addSlotToContainer(new Slot(entity, 2, 44, 53));
	this.addSlotToContainer(new Slot(entity, 3, 80, 35));
	this.addSlotToContainer(new Slot(entity, 4, 117, 17));
	this.addSlotToContainer(new Slot(entity, 5, 117, 35));
	this.addSlotToContainer(new Slot(entity, 6, 117, 53));

	for(int i = 0; i < 3; ++i) for(int j = 0; j < 9; ++j) this.addSlotToContainer(new Slot(inventory, j + i * 9 + 9, 8 + j * 18, 84 + i * 18));
	for(int i = 0; i < 9; ++i) this.addSlotToContainer(new Slot(inventory, i, 8 + i * 18, 142));
}

@Override
public void onContainerClosed(EntityPlayer playerIn) {
	super.onContainerClosed(playerIn);
	/*if(!world.isRemote) {
		ItemStack itemstack = this.tableInventory.getStackInSlotOnClosing(0);
		if (itemstack != null) {
			playerIn.dropPlayerItemWithRandomChoice(itemstack, false);
		}
	}*/
}

@Override
public boolean canInteractWith(EntityPlayer playerIn) {
	return true;
}
}

 

 

 

[spoiler=Tile Entity]

public class TileEntitySummoningTable extends TileEntity implements IUpdatePlayerListBox, IInventory {

private ItemStack[] inventory;

public TileEntitySummoningTable() {
	this.inventory = new ItemStack[7];
}

@Override
public void writeToNBT(NBTTagCompound nbt) {
	super.writeToNBT(nbt);
	NBTTagList nbttaglist = new NBTTagList();
	for(int i = 0; i < inventory.length; i++) {
		if(this.inventory[i] != null) {
			NBTTagCompound nbttagcompound1 = new NBTTagCompound();
			nbttagcompound1.setByte("Slot", (byte)i);
			this.inventory[i].writeToNBT(nbttagcompound1);
			nbttaglist.appendTag(nbttagcompound1);
		}
	}
	nbt.setTag("Items", nbttaglist);
}

@Override
public void readFromNBT(NBTTagCompound nbt) {
	super.readFromNBT(nbt);
	NBTTagList nbttaglist = nbt.getTagList("Items", 10);
	for(int i = 0; i < nbttaglist.tagCount(); i++) {
		NBTTagCompound nbttagcompound1 = nbttaglist.getCompoundTagAt(i);
		byte b0 = nbttagcompound1.getByte("Slot");
		if(b0 >= 0 && b0 < this.inventory.length)
			this.inventory[b0] = ItemStack.loadItemStackFromNBT(nbttagcompound1);
	} 
}

@Override
public void update() {
	/*if(inventory[0] != null && inventory[1] != null && inventory[2] != null && inventory[3] != null && inventory[4] != null && inventory[5] != null && inventory[6] != null) {
		Item item1 = inventory[0].getItem(), item2 = inventory[1].getItem(), item3 = inventory[2].getItem(), item4 = inventory[3].getItem(), item5 = inventory[4].getItem(), item6 = inventory[5].getItem(), item7 = inventory[6].getItem();
		if(item1 == EssenceItems.boilPowder && item2 == EssenceItems.boilPowder && item3 == EssenceItems.boilPowder && item4 == EssenceItems.blazingFireball && item5 == EssenceItems.boilPowder && item6 == EssenceItems.boilPowder && item7 == EssenceItems.boilPowder) {
			inventory[3].setItem(EssenceItems.blazierOrb);
		}
	}*/
}

@Override
public int getSizeInventory() {
	return inventory.length;
}

@Override
public ItemStack getStackInSlot(int i) {
	return inventory[i];
}

@Override
public String getName() {
	return "Summoning Table";
}

@Override
public boolean hasCustomName() {
	return true;
}

@Override
public IChatComponent getDisplayName() {
	return null;
}

@Override
public ItemStack decrStackSize(int i, int j) {
	if(inventory[i] != null) {
		if(inventory[i].stackSize <= j) {
			ItemStack itemstack = inventory[i];
			inventory = null;
			return itemstack;
		} else {
			inventory[i].stackSize -= j;
			return new ItemStack(inventory[i].getItem(), j, inventory[i].getMetadata());
		}
	} else {
		return null;
	}
}

@Override
public ItemStack getStackInSlotOnClosing(int index) {
	if(this.inventory[index] != null)  {
		ItemStack itemstack = inventory[index];
		this.inventory = null;
		return itemstack;
	} else {
		return null;
	}
}

@Override
public void setInventorySlotContents(int index, ItemStack stack) {
	boolean flag = stack != null && stack.isItemEqual(this.inventory[index]) && ItemStack.areItemStackTagsEqual(stack, this.inventory[index]);
	this.inventory[index] = stack;
	if(stack != null && stack.stackSize > this.getInventoryStackLimit())
		stack.stackSize = this.getInventoryStackLimit();
	if(index == 0 && !flag) this.markDirty();
}

@Override
public int getInventoryStackLimit() {
	return 64;
}

@Override
public boolean isUseableByPlayer(EntityPlayer player) {
	return true;
}

@Override
public void openInventory(EntityPlayer player) { }

@Override
public void closeInventory(EntityPlayer player) { }

@Override
public boolean isItemValidForSlot(int index, ItemStack stack) {
	return stack.getItem() != null;
}

@Override
public int getField(int id) {
	return 0;
}

@Override
public void setField(int id, int value) { }

@Override
public int getFieldCount() {
	return 0;
}

@Override
public void clear() {
	for(int i = 0; i < getSizeInventory(); i++) inventory[i] = null;
}
}

 

 

 

[spoiler=Crash]

[15:24:40] [server thread/ERROR] [FML]: A TileEntity type net.essence.blocks.tileentity.TileEntitySummoningTable has throw an exception trying to write state. It will not persist. Report this to the mod author
java.lang.NullPointerException
at net.essence.blocks.tileentity.TileEntitySummoningTable.writeToNBT(TileEntitySummoningTable.java:26) ~[TileEntitySummoningTable.class:?]
at net.minecraft.world.chunk.storage.AnvilChunkLoader.writeChunkToNBT(AnvilChunkLoader.java:382) [AnvilChunkLoader.class:?]
at net.minecraft.world.chunk.storage.AnvilChunkLoader.saveChunk(AnvilChunkLoader.java:183) [AnvilChunkLoader.class:?]
at net.minecraft.world.gen.ChunkProviderServer.saveChunkData(ChunkProviderServer.java:246) [ChunkProviderServer.class:?]
at net.minecraft.world.gen.ChunkProviderServer.saveChunks(ChunkProviderServer.java:305) [ChunkProviderServer.class:?]
at net.minecraft.world.WorldServer.saveAllChunks(WorldServer.java:938) [WorldServer.class:?]
at net.minecraft.server.MinecraftServer.saveAllWorlds(MinecraftServer.java:363) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.stopServer(MinecraftServer.java:395) [MinecraftServer.class:?]
at net.minecraft.server.integrated.IntegratedServer.stopServer(IntegratedServer.java:328) [integratedServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:531) [MinecraftServer.class:?]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_20]

 

 

You're putting null to the field 'inventory' when getting items from a slot. It should be inventory.

@Override
public ItemStack decrStackSize(int i, int j) {
	if(inventory[i] != null) {
		if(inventory[i].stackSize <= j) {
			ItemStack itemstack = inventory[i];
			inventory = null;
			return itemstack;
		} else {
			inventory[i].stackSize -= j;
			return new ItemStack(inventory[i].getItem(), j, inventory[i].getMetadata());
		}
	} else {
		return null;
	}
}

Oh wow.... I can't believe I'm stupid enough to not set the items to null but to set the actual field to null.... Thanks!