Pfthb

I'm trying to build a simple activity for messaging in android.

• I have a RecyclerView that list the messages and I set a ScrollListener on it.


• When the firstVisibleItem is the third of the list (RecyclerView stack from end), I will make a call to load other elements.


• I add this element to my array and I set a new adapter on my RecyclerView for the update.


• When I set the new adapter, the list starts one more time from the last message.


• So far I have tried to use scrollToPosition to go to the message where the user was before scrollListener was triggered, but still not work at all because the lastVisibleItem become 1 every time.

Is there a way to maintain the last firstVisible element and set this element as the top element after reset the Adapter?

This is the onCreateMethod.

@Override
protected void onCreate(Bundle savedInstanceState) 
 super.onCreate(savedInstanceState);
 setContentView(R.layout.chat);

 lastOffset = 0;
 requestSize = 20;

 loadMessage()

 mAdapter = new ChatAdapter(this,mess);
 llm = new LinearLayoutManager(this);
 llm.setStackFromEnd(true);
 mex_list.setLayoutManager(llm);
 mex_list.setAdapter(mAdapter);
 mex_list.addOnScrollListener(new RecyclerView.OnScrollListener() 
 @Override
 public void onScrolled(RecyclerView recyclerView, int dx, int dy) 
 super.onScrolled(recyclerView, dx, dy);
 int lastVisible = llm.findLastVisibleItemPosition();
 int firstVisible = llm.findFirstVisibleItemPosition();
 lastFirstVisibleItem = firstVisibleItem; //lastFirstVisibleItem is a global variable
 if(firstVisible <= 3)
 if(!loading) 
 loading = true;
 loadMessage();
 
 
 Log.d("Test Scroll", "LAST: "+ lastVisible+" FIRST: "+firstVisible);
 
 );

This is where the laodMessage() result was managed.

 public void manageResult(Object pr, int caller) 
 if(caller == MESSAGES_REQ)
 if(mess == null)
 mess = new ArrayList<>();
 ArrayList<Message> tail = (ArrayList<Message>) pr;

 if(tail != null && tail.size() > 0) 
 lastOffset += tail.size();
 mess.addAll(tail);
 mAdapter = new ChatAdapter(ctx, mess);
 mex_list.setAdapter(mAdapter);
 

 llm.scrollToPosition(lastFirstVisibleItem);//lastFirstVisibleItem became always 1
 spinner.setVisibility(View.GONE);
 printEmpMex(View.GONE);
 mex_list.setVisibility(View.VISIBLE);
 loading = false;
 

This is the ChatAdapter.

public class ChatAdapter extends RecyclerView.Adapter<ChatAdapter.ViewHolder> 

private ArrayList<Message> listOfMessages;
private static Context ctx;

private static final int SENT = 100;
private static final int RECIVED = 200;

public static class ViewHolder extends RecyclerView.ViewHolder 
 public TextView text;
 public TextView hour;


 public ViewHolder(View v) 
 super(v);
 text = (TextView) v.findViewById(R.id.text_body);
 hour = (TextView) v.findViewById(R.id.time);
 

 void bind(Message m)
 text.setText(m.getBody());
 hour.setText(formatDateAndHour(m.getDate()));
 


public ChatAdapter(Context ctx, ArrayList<Message> m) 
 listOfMessages = m;
 this.ctx = ctx;


@Override
public ViewHolder onCreateViewHolder(ViewGroup parent,
 int viewType) 

 View view;
 if (viewType == SENT) 

 view = LayoutInflater.from(parent.getContext())
 .inflate(R.layout.single_mex_sent, parent, false);
 return new ViewHolder(view);

 
 else if (viewType == RECIVED)

 view = LayoutInflater.from(parent.getContext())
 .inflate(R.layout.single_mex_recived, parent, false);
 return new ViewHolder(view);
 

 return null;


@Override
public void onBindViewHolder(ViewHolder holder, int position) 
 Message mex = listOfMessages.get(position);
 holder.bind(mex);


@Override
public int getItemCount() 
 return listOfMessages.size();


@Override
public int getItemViewType(int position) 
 Message m = listOfMessages.get(position);
 if(m.getSender().getIdUser().equals(loggedUser.getIdUser()))
 return SENT;
 else
 return RECIVED;

I really don't know how to make it work.
Every approach is welcome.

Thanks in advance.