UsersFragment.java

package com.codewithharry.firebase;

import android.content.Intent;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.SearchView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.core.view.MenuItemCompat;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
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 java.util.ArrayList;

import com.codewithharry.firebase.adapters.AdapterUsers;
import com.codewithharry.firebase.models.ModelUser;

public class UsersFragment extends Fragment {

    RecyclerView recyclerView;
    AdapterUsers adapterUsers;
    ArrayList<ModelUser> userList;

    //FireBase aUth
    FirebaseAuth firebaseAuth;

    public UsersFragment() {
        // Required empty public constructor
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_users, container, false);

        //init
        firebaseAuth = FirebaseAuth.getInstance();

        //init recyclerView
        recyclerView = view.findViewById(R.id.users_recyclerview);

        //Set it's properties
        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));

        //init user list
        userList = new ArrayList<>();
        //get all user
        getAllUsers();

        return view;
    }

    private void getAllUsers() {
        //get current user
        FirebaseUser fUser = FirebaseAuth.getInstance().getCurrentUser();
        //get path of database named "users" containing users info
        DatabaseReference ref = FirebaseDatabase.getInstance().getReference("Users");
        //get all data from path
        ref.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                userList.clear();
                for (DataSnapshot ds: dataSnapshot.getChildren()) {
                    ModelUser modelUser = ds.getValue(ModelUser.class);

                    //get all users except the currently signed in user
                    if (!modelUser.getUid().equals(fUser.getUid())) {
                        userList.add(modelUser);
                    }

                    //adapter
                    adapterUsers = new AdapterUsers(getContext(), userList);
                    //set adapter to recycler view
                    recyclerView.setAdapter(adapterUsers);
                }
            }

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

            }
        });
    }


    private void searchUsers(String query) {
        //get current user
        FirebaseUser fUser = FirebaseAuth.getInstance().getCurrentUser();
        //get path of database named "users" containing users info
        DatabaseReference ref = FirebaseDatabase.getInstance().getReference("Users");
        //get all data from path
        ref.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                userList.clear();
                for (DataSnapshot ds: dataSnapshot.getChildren()) {
                    ModelUser modelUser = ds.getValue(ModelUser.class);

                    /*Conditions to fulfill search:
                    * 1]user is not the current user
                    * The user name or email text entered is in SearchView(case sensitive)*/
                    //get all searched users except the currently signed in user
                    assert modelUser != null;
                    assert fUser != null;
                    if (!modelUser.getUid().equals(fUser.getUid())) {

                        if(modelUser.getName().toLowerCase().contains(query.toLowerCase()) ||
                                modelUser.getEmail().toLowerCase().contains(query.toLowerCase())){
                            userList.add(modelUser);
                        }

                    }

                    //adapter
                    adapterUsers = new AdapterUsers(getActivity().getApplicationContext(), userList);
                    //refresh adapter
                    adapterUsers.notifyDataSetChanged();
                    //set adapter to recycler view
                    recyclerView.setAdapter(adapterUsers);
                }
            }

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

            }
        });
    }

    private void checkUserStatus() {
        //Get current user
        FirebaseUser user = firebaseAuth.getCurrentUser();
        if (user != null) {
            //User is signed in stay here
            //set email of logged in user
            //mProfileTv.setText(user.getEmail());
        } else {
            //User not signed in go to main activity
            startActivity(new Intent(getActivity(), MainActivity.class));
            getActivity().finish();
        }
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        setHasOptionsMenu(true);//to show menu options in fragments
        super.onCreate(savedInstanceState);
    }

    /*Inflate options menu*/

    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        inflater.inflate(R.menu.menu_main, menu);

        //hide addpost icon from this fragment
        menu.findItem(R.id.action_add_post).setVisible(false);

        //SearchView
        MenuItem item = menu.findItem(R.id.action_search);
        SearchView searchView = (SearchView) MenuItemCompat.getActionView(item);

        //SearchView Listener
        searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
            @Override
            public boolean onQueryTextSubmit(String s) {
                //called when user presses search button from keyboard
                //if search query is not empty then search
                if(!TextUtils.isEmpty(s.trim())){
                    searchUsers(s);
                } else {
                    //search text is empty
                    getAllUsers();
                }
                return false;
            }

            @Override
            public boolean onQueryTextChange(String s) {
                //called when user presses any letter
                //if search query is not empty then search
                if(!TextUtils.isEmpty(s.trim())){
                    searchUsers(s);
                } else {
                    //search text is empty
                    getAllUsers();
                }
                return false;
            }
        });

        super.onCreateOptionsMenu(menu, inflater);
    }

    /*Handle menu item clicks*/

    @Override
    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
        //get item id
        int id = item.getItemId();
        if(id == R.id.action_logout){
            firebaseAuth.signOut();
            checkUserStatus();
        }

        return super.onOptionsItemSelected(item);
    }

}