I made a TileEntity with 1 slot. When I do things with the slot normally, it works. But when loading the world, the slot is buggy until I empty the slot, leave the GUI, and insert the item back. I also get an error message when loading the mod.

 

@Override
	public void setInventorySlotContents(int slot, ItemStack stack) {
		if (slot > getSizeInventory() || slot < 0)
			return;

		if (stack != null && stack.stackSize > this.getInventoryStackLimit())
			stack.stackSize = this.getInventoryStackLimit();

		if (stack != null && stack.stackSize == 0)
			stack = null;

		this.slots[slot] = stack;
		
		if(getStackInSlot(0) != null){
			worldObj.setBlockMetadataWithNotify(xCoord, yCoord, zCoord, getStackInSlot(0).getItemDamage() + 1, 2);
		}else{
			worldObj.setBlockMetadataWithNotify(xCoord, yCoord, zCoord, 0, 2);
		}
		this.markDirty();
	}
	
	@Override
	public void readFromNBT(NBTTagCompound tag) {
		super.readFromNBT(tag);

	    NBTTagList list = tag.getTagList("Items", 10);
	    for (int i = 0; i < list.tagCount(); ++i) {
	        NBTTagCompound stackTag = list.getCompoundTagAt(i);
	        ItemStack item = ItemStack.loadItemStackFromNBT(stackTag);
	        int slot = stackTag.getByte("Slot") & 255;
	        System.out.println(slot + "/" + item);
	        this.setInventorySlotContents(slot, item);
	    }
	}
	
	@Override
	public void writeToNBT(NBTTagCompound tag) {
		super.writeToNBT(tag);

	    NBTTagList list = new NBTTagList();
	    for (int i = 0; i < this.getSizeInventory(); ++i) {
	        if (this.getStackInSlot(i) != null) {
	            NBTTagCompound stackTag = new NBTTagCompound();
	            stackTag.setByte("Slot", (byte) i);
	            this.getStackInSlot(i).writeToNBT(stackTag);
	            list.appendTag(stackTag);
	        }
	    }
	    tag.setTag("Items", list);
	}

that is my code.

 

The error message is this:

A TileEntity waterGenerator(com.deerangle.tile.TileEntityWaterGen) has thrown an exception during loading, its state cannot be restored. Report this to the mod author
java.lang.NullPointerException
	at com.deerangle.tile.TileEntityWaterGen.setInventorySlotContents(TileEntityWaterGen.java:118) ~[TileEntityWaterGen.class:?]
	at com.deerangle.tile.TileEntityWaterGen.readFromNBT(TileEntityWaterGen.java:135) ~[TileEntityWaterGen.class:?]
	at net.minecraft.tileentity.TileEntity.createAndLoadEntity(TileEntity.java:135) [TileEntity.class:?]
	at net.minecraft.world.chunk.storage.AnvilChunkLoader.loadEntities(AnvilChunkLoader.java:525) [AnvilChunkLoader.class:?]
	at net.minecraftforge.common.chunkio.ChunkIOProvider.callStage2(ChunkIOProvider.java:41) [ChunkIOProvider.class:?]
	at net.minecraftforge.common.chunkio.ChunkIOProvider.callStage2(ChunkIOProvider.java:12) [ChunkIOProvider.class:?]
	at net.minecraftforge.common.util.AsynchronousExecutor.skipQueue(AsynchronousExecutor.java:344) [AsynchronousExecutor.class:?]
	at net.minecraftforge.common.util.AsynchronousExecutor.getSkipQueue(AsynchronousExecutor.java:302) [AsynchronousExecutor.class:?]
	at net.minecraftforge.common.chunkio.ChunkIOExecutor.syncChunkLoad(ChunkIOExecutor.java:12) [ChunkIOExecutor.class:?]
	at net.minecraft.world.gen.ChunkProviderServer.loadChunk(ChunkProviderServer.java:144) [ChunkProviderServer.class:?]
	at net.minecraft.world.gen.ChunkProviderServer.loadChunk(ChunkProviderServer.java:119) [ChunkProviderServer.class:?]
	at net.minecraft.server.MinecraftServer.initialWorldChunkLoad(MinecraftServer.java:305) [MinecraftServer.class:?]
	at net.minecraft.server.integrated.IntegratedServer.loadAllWorlds(IntegratedServer.java:79) [IntegratedServer.class:?]
	at net.minecraft.server.integrated.IntegratedServer.startServer(IntegratedServer.java:96) [IntegratedServer.class:?]
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:445) [MinecraftServer.class:?]
	at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:752) [MinecraftServer$2.class:?]

 

Edited November 24, 20177 yr by deerangle
solved!

Thank you! I got it working now... worldObj was null!