CODEWITHSUNDEEP
androidandroid-recyclerview
Alezis
Alezis

Reputation: 1222

RecyclerView add items on top and continue scrolling

I have a Fragment with a RecyclerView. It works as a chat.

I request to my backend the last 50 messages and I load them in the recycler view

LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity());
layoutManager.setStackFromEnd(true);
recyclerView.setLayoutManager(layoutManager);

mAdapter = new ChatMessagesAdapter(recyclerView, messages, getActivity());
recyclerView.setAdapter(mAdapter);
recyclerView.getLayoutManager().scrollToPosition(messages.size()-1);

mAdapter.notifyDataSetChanged();

Then, when I scroll up I request more messages with OnScrollListener and I load them 

messages.addAll(0, oldMessages);
mAdapter.notifyDataSetChanged();
mAdapter.setLoaded();
recyclerView.getLayoutManager().scrollToPosition((oldMessages.size()) -1);

But as I set the the recyclerView in the first load with

layoutManager.setStackFromEnd(true);

when I load the old messages the scroll moves first item shown(before the last) to the bottom.

How can I add old messages on top and continue the scrolling like if the items were there from the first load? Without move the focus to the bottom

Upvotes: 2

Views: 3235

Answers (1)

SpiritCrusher
SpiritCrusher

Reputation: 21053

Use notifyItemRangeInserted instead of notifyDataSetChanged.

Use below code to update your adapter:

public void addList(List<ChatMessage> items) {
    chatMessages.addAll(0, items);
    notifyItemRangeInserted(0,items.size());
    notifyItemChanged(items.size());//Only  To update the last top item cause in my case it was the date header so i need to notify it 
}

Upvotes: 8

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