[译]RecyclerView.ViewHolder - getLayoutPosition vs getAdapterPosition

【未完成】
When adapter contents change (and you call notify***) RecyclerView requests a new layout. From that moment, until layout system decides to calculate a new layout (<16 ms), the layout position and adapter position may not match because layout has not reflected adapter changes yet.

当adapter中的数据发生改变（当你调用notify***），RecyclerView会重新进行layout，此时，layout position和adpater position是不一样的。

Be careful though, if you are calling notifyDataSetChanged, because it invalidates everything, RecyclerView does not know that ViewHolder’s adapter position until next layout is calculated. In that case, getAdapterPosition will return RecyclerView#NO_POSITION (-1).

But lets say if you’ve called notifyItemInserted(0), the getAdapterPosition of ViewHolder which was previously at position 0 will start returning 1 immediately. So as long as you are dispatching granular notify events, you are always in good state (we know adapter position even though new layout is not calculated yet).

Another example, if you are doing something on user click, if getAdapterPosition returns NO_POSITION, it is best to ignore that click because you don’t know what user clicked (unless you have some other mechanism, e.g. stable ids to lookup the item).

Edit For When Layout Position is Good

Lets say you are using LinearLayoutManager and want to access the ViewHolder above the currently clicked item. In that case, you should use layout position to get the item above.

mRecyclerView.findViewHolderForLayoutPosition(myViewHolder.getLayoutPosition() - 1)
You have to use layout position because it matches what user is currently seeing on the screen.