findLastVisibleItemPositions
Returns the adapter position of the last visible view for each span.
Note that, this value is not affected by layout orientation or item order traversal. (setReverseLayout). Views are sorted by their positions in the adapter, not in the layout.
If RecyclerView has item decorators, they will be considered in calculations as well.
StaggeredGridLayoutManager may pre-cache some views that are not necessarily visible. Those views are ignored in this method.
Return
The adapter position of the last visible item in each span. If a span does not have any items, NO_POSITION is returned for that span.
Parameters
into
An array to put the results into. If you don't provide any, LayoutManager will create a new one.