I have 2-column RecyclerView
based on StaggeredGridLayoutManager
.
When changing a content of the 1 item and triggering DiffUtil
the RecyclerView is jumping to the 2 item. But when scrolling up it is possible to see 1 element and empty space, during the scroll items are transforming to a natural order. Also, the amount of items in the diff list is the same.
How to avoid this annoying behavior and to keep scrolling position during diffUtil?
val layoutManager = StaggeredGridLayoutManager(2, StaggeredGridLayoutManager.VERTICAL)
recyclerView.layoutManager = layoutManager
recyclerView.itemAnimator = null
recyclerView.setHasFixedSize(true)
recyclerView.setItemViewCacheSize(if (App.isTablet()) 3 else 2)
public void diffUpdate(List<T> newList) {
if (getCollection().size() == 0) {
addAll(newList);
notifyDataSetChanged();
} else {
DiffCallback diffCallback = new DiffCallback<T>(getCollection(), newList);
DiffUtil.DiffResult diffResult = DiffUtil.calculateDiff(diffCallback);
clear();
addAll(newList);
diffResult.dispatchUpdatesTo(this);
}
}
The problem was with the implementation of DiffCallback. Earlier I used hashes:
@Override public boolean areItemsTheSame(int oldItemPosition, int newItemPosition) {
T oldItem = oldList.get(oldItemPosition);
T newItem = newList.get(newItemPosition);
boolean areTheSameInstance = oldItem == newItem;
boolean hasTheSameType = oldItem.getClass().equals(newItem.getClass());
boolean hasTheSameHash = oldItem.hashCode() == newItem.hashCode();
return areTheSameInstance || hasTheSameType && hasTheSameHash;
}
This was triggering recreation of the entire view in the RecyclerView and probably measuring in the StaggeredGridLayoutManager.
After I have changed it to id check, diffCalbback has started to triggering only rendering of the view in the RecyclerView.
return ((Model) oldItem).id() == ((Model) newItem).id();