Hello, so I am trying to make an item lock that prevents you from dropping items so you don't accidentally lose them. I save NBT data to it, but I have a problem. If I try to save data to a block I've already made, which saves the NBT when you break it and shows it in the tooltip, it gives a null pointer exception.

Add information and getItemCount methods in my block class:

@Override
public void addInformation(ItemStack itemstack, @Nullable World worldIn, List<String> tooltip, ITooltipFlag flagIn) {
    tooltip.add("Makes cobblestone and compressed cobblestone with upgrades at a stack per tick. Uses LOADS of power when upgraded.");
    tooltip.add("Will auto-eject items.");
    NBTTagCompound tagCompound = itemstack.getTagCompound();
    if (tagCompound != null) {
        int energy = tagCompound.getInteger("energy");
       //Crashing Line int sizeIn = getItemCount(tagCompound, "itemsIn");
        int sizeOut = getItemCount(tagCompound, "itemsOut");
        String translated = I18n.format("message.tm.cobble_generator", energy, sizeIn, sizeOut);
        translated = COMPILE.matcher(translated).replaceAll("\u00a7");
        Collections.addAll(tooltip, StringUtils.split(translated, "\n"));
    }
}
private int getItemCount(NBTTagCompound tagCompound, String itemsIn2) {
    int sizeIn = 0;
    NBTTagCompound compoundIn = (NBTTagCompound) tagCompound.getTag(itemsIn2);
   //Crashing line NBTTagList itemsIn = compoundIn.getTagList("Items", Constants.NBT.TAG_COMPOUND);
    for (int i = 0; i < itemsIn.tagCount(); i++) {
        NBTTagCompound itemTags = itemsIn.getCompoundTagAt(i);
        if (!new ItemStack(itemTags).isEmpty()) {
            sizeIn++;
        }
    }
    return sizeIn;
}

I think this is because of the "NBTTagCompound tagCompound = itemstack.getTagCompound();" line which gets all the NBT data, including the locking NBT boolean.

Is there anything I can do to fix this?

 

Note: This is a duplicate because I posted this in the wrong place. Sorry.

Edited August 24, 20196 yr by TesterTesting135
Solved

tagCompound.getTag(itemsIn2);

 

This is returning null. So your sub compound does not exist. Make sure you got all the keys right

Woops, thank you so much!