ItemStack Gui NBT isn't saving after GUI close

[SamTebbs33]

Hi, I'm making an item which opens up a GUI when right-clicked. When a certain item is placed in a slot in the itemstack's container, a key's value is set to true in the itemstack's nbt.

 

The only problem is that the nbt doesn't seem to be saving on GUI close, it does however save while the GUI is open. I have ensured that the relevant nbt keys are created in the onCreate method in net.minecraft.item.Item.

 

I have another item which uses nbt but not with a GUI and that works fine. Does anyone know how I would go about fixing it?

 

P.S I haven't shown my source code as I'm a bit reluctant to make it public at the moment, if you need to see it, please PM me.

 

Thanks in advance

[SamTebbs33]

Thank you for the help!

That must be the problem, would I have to send some kind of packet to the server to allow the GUI to modify NBT data?