Container problems

[MichaelVitrio]

These might be relatively basic questions but since I can't find any clue in vanilla code and I did try to look up on internet with no luck, I'm here seeking help from the community.

 

1. What does the return value of Container#transferStackInSlot mean and what might possibly cause the game to crash upon calling this method?

 

2. Is Slot#isItemValid supposed to check the size of the current ItemStack in the slot or it should just return true whenever the ItemStack is allowed to be in the slot?

 

3. In class ItemStackHandler (I assume it's sort of a default implementation of IItemHandler, is that correct though), there're two empty methods onLoad() and onContentsChanged(), which don't override any super class methods but are called within other methods. Are they supposed to perform any functionality or they're just some place holders?

 

Thanks a lot for your help

[Draco18s]

1) It is the remaining items after attempting to insert (e.g. you got a stack of 64 wood, but only had room for 32, the remaining 32 are returned). The game crashes if you return null because ItemStacks are @NonNull

 

2) Not usually. I suppose you could, but why?

 

3) Those methods are there for subclasses to implement. There are no vanilla (well Forge, actually) subclasses. The Block class does this all the time.

Edited February 19, 2018 by Draco18s