ChatRoomActivity

package com.example.bilkentcompanion.chat;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.firebase.ui.database.FirebaseRecyclerOptions;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import de.hdodenhof.circleimageview.CircleImageView;



public class ChatRoomActivity extends AppCompatActivity {
    private View privateChatsView;
    private RecyclerView chatsList;

    private DatabaseReference chatsRef, usersRef;
    private FirebaseAuth mAuth;
    private String currentUserID;

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

        mAuth = FirebaseAuth.getInstance();
        currentUserID = mAuth.getCurrentUser().getUid();
        chatsRef = FirebaseDatabase.getInstance().getReference().child("Contacts").child( currentUserID);
        usersRef = FirebaseDatabase.getInstance().getReference().child("Users");

        chatsList = (RecyclerView) findViewById(R.id.chats_list2);
        chatsList.setLayoutManager( new LinearLayoutManager( ChatRoomActivity.this));
    }

    @Override
    protected void onStart() {
        super.onStart();

        FirebaseRecyclerOptions<Contacts> options = new FirebaseRecyclerOptions.Builder<Contacts>()
                .setQuery( chatsRef, Contacts.class).build();

        FirebaseRecyclerAdapter<Contacts, ContactsFragment.ChatsViewHolder> adapter  = new FirebaseRecyclerAdapter<Contacts, ContactsFragment.ChatsViewHolder>( options) {
            @Override
            protected void onBindViewHolder(@NonNull final ContactsFragment.ChatsViewHolder holder, int position, @NonNull Contacts model) {
                final String usersIDs = getRef( position).getKey();

                usersRef.child( usersIDs).addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                        if ( dataSnapshot.exists())
                        {
                            if ( dataSnapshot.hasChild("image"))
                            {
                                final String retImage = dataSnapshot.child("image").getValue().toString();
                            }
                            final String retName = dataSnapshot.child("name").getValue().toString();
                            final String retStatus = dataSnapshot.child("image").getValue().toString();

                            holder.userName.setText( retName);

                            holder.itemView.setOnClickListener(new View.OnClickListener() {
                                @Override
                                public void onClick(View v)
                                {
                                    Intent chatIntent = new Intent( ChatRoomActivity.this, ChatActivity.class);
                                    chatIntent.putExtra("visit_user_id", usersIDs);
                                    chatIntent.putExtra("visit_user_name", retName);
                                    startActivity( chatIntent);
                                }
                            });
                        }
                    }

                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {

                    }
                });
            }

            @NonNull
            @Override
            public ContactsFragment.ChatsViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
                View view = LayoutInflater.from( viewGroup.getContext()).inflate(R.layout.users_display_layout, viewGroup, false);
                return new ContactsFragment.ChatsViewHolder( view);
            }
        };
        chatsList.setAdapter( adapter);
        adapter.startListening();
    }

    public static class ChatsViewHolder extends RecyclerView.ViewHolder
    {
        CircleImageView profileImage;
        TextView userStatus, userName;

        public ChatsViewHolder(@NonNull View itemView)
        {
            super( itemView);

            profileImage = itemView.findViewById(R.id.users_profile_image);
            userStatus = itemView.findViewById(R.id.user_status);
            userName = itemView.findViewById(R.id.user_profile_name);
        }
    }
}