NestedRecyclerView | TAB ceiling effect through two-layer nesting | RecyclerView library

RecyclerViews work by recycling a handful of ViewHolder objects, and updating them to display a different item's data. That happens in onBindViewHolder, which is where you're setting it up to display the data with your holder.setItems(curRoutineItem) call, right?

But each time you bind a view holder, this is what you're doing:

• getting the RoutineModel for the current position
• clearing its arrayListDetail and adding a single, new ``RoutineDetailModel```
• creating a new RoutineDetailAdapter which only contains that single RoutineDetailModel, and setting that on the ViewHolder's RecyclerView, replacing what was already there
• adding a click listener that adds another RoutineDetailModel to the RoutineModel and adapter (both of which will be cleared and recreated next time onBindViewHolder is called)

So I don't know specifically where your problem lies, but you're not actually storing this state with the added items - it gets wiped every time onBindViewHolder is called, whenever an item scrolls into view.

If you're saying that you click the button and nothing happens in the RecyclerView without calling setAdapter again, then I'm not sure why that would happen - at that point detailAdapter is referencing the adapter in the recycler view, and you are adding another item (technically replacing its items with the same list of one plus another one).

But if you mean you scroll the list and your items disappear, yeah that's going to happen, because you delete them every time the item scrolls back into view. This stuff looks like data initialisation:

Try adding app:behavior_overlapTop="0dp" in your nested scroll view and also add some elevation to the nested scroll view.

onNestedScrollAccepted() was added in API 21. You can't use it in lower API levels.