Android Firebase chat RecyclerView automatically scrolls down when adding a new item

Question

im is developing android chat using firebase.

I tried to investigate this problem, but I cannot find good solutions.

I hope someone can help me.

my problem: I want RecyclerView to automatically scroll if a new item is added.

here is my code.

@Nullable @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){ View rootView = inflater.inflate(R.layout.chatlayoutchat, container, false); Connectivity connectivity=new Connectivity(); if(connectivity.isConnected(getActivity())) { if(getArguments() != null) { Firebase.setAndroidContext(this.getActivity()); String ccustomersid = getArguments().getString("customersid"); String creferralae = getArguments().getString("referralae"); String ccustomersname = getArguments().getString("customersname"); customersid = ccustomersid; referralae = creferralae; customersname = ccustomersname; Firebase.setAndroidContext(this.getActivity()); editText = (EditText) rootView.findViewById(R.id.editText); sendbutton = (Button) rootView.findViewById(R.id.button); mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recycler_view); RecyclerView.LayoutManager layoutmgr = new LinearLayoutManager(getActivity()); mRecyclerView.setLayoutManager(layoutmgr); mRecyclerView.setItemAnimator(new DefaultItemAnimator()); final LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity()); //linearLayoutManager.setReverseLayout(true); linearLayoutManager.setStackFromEnd(true); mRecyclerView.setLayoutManager(linearLayoutManager); from_user = customersid; to_user = referralae; LoggedInUser = customersname; //Log.v("NODE CREATED:", from_user + " " + to_user); ref_chatchildnode1 = firebase_chatnode.child(from_user + " " + to_user); //ref_chatchildnode2 = firebase_chatnode.child(to_user + " " + from_user); sendbutton.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { newmsg = editText.getText().toString().trim(); ChatModel m = new ChatModel(); m.setSender(LoggedInUser); m.setMessage(newmsg); ref_chatchildnode1.push().setValue(m); //ref_chatchildnode2.push().setValue(m); editText.setText(""); } }); ref_chatchildnode1.addChildEventListener(new ChildEventListener() { @Override public void onChildAdded(DataSnapshot dataSnapshot, String s) { ChatModel chatmsg = dataSnapshot.getValue(ChatModel.class); chatmsgsList.add(chatmsg); } @Override public void onChildChanged(DataSnapshot dataSnapshot, String s) { } @Override public void onChildRemoved(DataSnapshot dataSnapshot) { } @Override public void onChildMoved(DataSnapshot dataSnapshot, String s) { } @Override public void onCancelled(FirebaseError firebaseError) { } }); } }else{ nointernet(); } showGlobalContextActionBar(); return rootView; } @Override public void onStart() { super.onStart(); mFirebaseAdapter1 = new FirebaseRecyclerAdapter<ChatModel, ChatMessageViewHolder>(ChatModel.class, R.layout.textview, ChatMessageViewHolder.class, ref_chatchildnode1) { @Override protected void populateViewHolder(ChatMessageViewHolder chatMessageViewHolder, ChatModel m, int i) { chatMessageViewHolder.sender.setText(m.getSender()); chatMessageViewHolder.msg.setText(m.getMessage()); } }; mRecyclerView.setAdapter(mFirebaseAdapter1); } 

Answer 1

Take a look at step 6 of the Firebase codec for Android , which uses AdapterDataObserver to do this:

 mFirebaseAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() { @Override public void onItemRangeInserted(int positionStart, int itemCount) { super.onItemRangeInserted(positionStart, itemCount); int friendlyMessageCount = mFirebaseAdapter.getItemCount(); int lastVisiblePosition = mLinearLayoutManager.findLastCompletelyVisibleItemPosition(); // If the recycler view is initially being loaded or the // user is at the bottom of the list, scroll to the bottom // of the list to show the newly added message. if (lastVisiblePosition == -1 || (positionStart >= (friendlyMessageCount - 1) && lastVisiblePosition == (positionStart - 1))) { mMessageRecyclerView.scrollToPosition(positionStart); } } }); 

Answer 2

Just try the code below:

  @Override public void onStart() { super.onStart(); mFirebaseAdapter1 = new FirebaseRecyclerAdapter<ChatModel, ChatMessageViewHolder>(ChatModel.class, R.layout.textview, ChatMessageViewHolder.class, ref_chatchildnode1) { @Override protected void populateViewHolder(ChatMessageViewHolder chatMessageViewHolder, ChatModel m, int i) { chatMessageViewHolder.sender.setText(m.getSender()); chatMessageViewHolder.msg.setText(m.getMessage()); } }; mRecyclerView.setAdapter(mFirebaseAdapter1); if (mFirebaseAdapter1 != null) { mRecyclerView.postDelayed(new Runnable() { @Override public void run() { mRecyclerView.smoothScrollToPosition(mFirebaseAdapter1.getItemCount() - 1); } }, 5); } } 

Answer 3

I know this is an old topic, but perhaps it will be useful.

In the place where you are adding a new message:

 yourRVAdapter.addMessage("New message") val position = yourRVAdapter.itemCount.minus(1) // itemCount will return the size of RV items //Now just call your recyclerView.scrollToPosition(int) chatRV.scrollToPosition(position)