This has nothing to do with Android Studio updates

You see this line here

user.getId().equals(firebaseUser.getUid())

This is throwing a NullPointerException, as it’s cleared at the log, to avoid such case you should change it to

if(user.getId() != null && user.getId().equals(firebaseUser.getUid())

This should avoid the crash but probably means that you don’t assign id correctly for the users in your database (because technically all users should have ids)

Please help, I dont really know how this happened, my app was working fine, then an update from Android Studio and a dependencie and this happened, I have tried putting everything as it was, but still nothing, please help. The activity below is not the Main Activity the app displays when opening, it is the one that appears after the user authenticates.

Process: com.Interactive.textmefriends, PID: 7638
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.lang.String.equals(java.lang.Object)' on a null object reference
    at com.Interactive.textmefriends.Fragments.UsersFragment$3.onDataChange(UsersFragment.java:126)
    at com.google.firebase.database.core.ValueEventRegistration.fireEvent(com.google.firebase:[email protected]@19.2.1:75)
    at com.google.firebase.database.core.view.DataEvent.fire(com.google.firebase:[email protected]@19.2.1:63)
    at com.google.firebase.database.core.view.EventRaiser$1.run(com.google.firebase:[email protected]@19.2.1:55)
    at android.os.Handler.handleCallback(Handler.java:883)
    at android.os.Handler.dispatchMessage(Handler.java:100)
    at android.os.Looper.loop(Looper.java:214)
    at android.app.ActivityThread.main(ActivityThread.java:7356)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

The Activity

package com.Interactive.textmefriends;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;
import androidx.fragment.app.FragmentPagerAdapter;
import androidx.viewpager.widget.ViewPager;

import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;

import com.Interactive.textmefriends.Fragments.ChatsFragment;
import com.Interactive.textmefriends.Fragments.ProfileFragment;
import com.Interactive.textmefriends.Fragments.UsersFragment;
import com.Interactive.textmefriends.Model.Chat;
import com.Interactive.textmefriends.Model.User;
import com.bumptech.glide.Glide;
import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdView;
import com.google.android.gms.ads.MobileAds;
import com.google.android.material.tabs.TabLayout;
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 java.util.HashMap;

import de.hdodenhof.circleimageview.CircleImageView;

public class Main2Activity extends AppCompatActivity {

    CircleImageView profile_image;
    TextView username;

    FirebaseUser firebaseUser;
    DatabaseReference reference;

    private AdView mAdView;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        MobileAds.initialize(this, "ca-app-pub-8087632256608585~2089051412");
        mAdView = findViewById(R.id.adView);
        AdRequest adRequest = new AdRequest.Builder().build();
        mAdView.loadAd(adRequest);


        Toolbar toolbar = findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setTitle("");

        profile_image = findViewById(R.id.profile_image);
        username = findViewById(R.id.username);

        firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
        reference = FirebaseDatabase.getInstance().getReference("Users").child(firebaseUser.getUid());


        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                User user = dataSnapshot.getValue(User.class);
                username.setText(user.getUsername());
                if (user.getImageURL().equals("default"))  {
                    profile_image.setImageResource(R.mipmap.ic_launcher);
                }
                else {
                    Glide.with(getApplicationContext()).load(user.getImageURL()).into(profile_image);
                }
            }

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

            }
        });


        final TabLayout tabLayout = findViewById(R.id.tab_layout);
        final ViewPager viewPager = findViewById(R.id.view_pager);

        reference = FirebaseDatabase.getInstance().getReference("Chats");
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                ViewPagerAdapter viewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
                int unread = 0;
                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                    Chat chat =  snapshot.getValue(Chat.class);
                    if (chat.getReceiver().equals(firebaseUser.getUid()) && !chat.isIsseen()) {
                        unread++;
                    }
                }

                if (unread == 0) {
                    viewPagerAdapter.addFragment(new ChatsFragment(), "Chats");
                }
                else {
                    viewPagerAdapter.addFragment(new ChatsFragment(), "("+unread+") Chats");
                }

                viewPagerAdapter.addFragment(new UsersFragment(), "Users");  //setTitle(R.string.fragment_users_title)
                viewPagerAdapter.addFragment(new ProfileFragment(), "Profile");  //setTitle(R.string.fragment_profile_title)

                viewPager.setAdapter(viewPagerAdapter);

                tabLayout.setupWithViewPager(viewPager);

            }

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

            }
        });

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId())  {

            case R.id.logout:
                FirebaseAuth.getInstance().signOut();
                startActivity(new Intent(Main2Activity.this, StartActivity.class).setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP));
                return true;
        }

        return false;
    }


    class ViewPagerAdapter extends FragmentPagerAdapter {


        private ArrayList<Fragment> fragments;
        private ArrayList<String> titles;

        ViewPagerAdapter(FragmentManager fm) {
            super(fm);
            this.fragments =  new ArrayList<>();
            this.titles = new ArrayList<>();
        }

        @NonNull
        @Override
        public Fragment getItem(int position) {
            return fragments.get(position);
        }

        @Override
        public int getCount() {
            return fragments.size();
        }

        public void addFragment(Fragment fragment, String title)  {
            fragments.add(fragment);
            titles.add(title);
        }

        @Nullable
        @Override
        public CharSequence getPageTitle(int position) {
            return titles.get(position);
        }
    }

    private void status(String status) {
        reference = FirebaseDatabase.getInstance().getReference("Users").child(firebaseUser.getUid());

        HashMap<String, Object> hashMap = new HashMap<>();
        hashMap.put("status", status);

        reference.updateChildren(hashMap);
    }

    @Override
    protected void onResume() {
        super.onResume();
        status("online");
    }

    @Override
    protected void onPause() {
        super.onPause();
        status("offline");
    }
}

This is where supposedly the error is

package com.Interactive.textmefriends.Fragments;

import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.text.Editable;
import android.text.TextWatcher;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;

import com.Interactive.textmefriends.Adapter.UserAdapter;
import com.Interactive.textmefriends.Model.User;
import com.Interactive.textmefriends.R;
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.Query;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;
import java.util.List;

public class UsersFragment extends Fragment {

    private RecyclerView recyclerView;

    private UserAdapter userAdapter;
    private List<User> mUsers;

    EditText search_users;


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

        recyclerView = view.findViewById(R.id.recycler_view);
        recyclerView.setHasFixedSize(true);
        recyclerView.setLayoutManager(new LinearLayoutManager(getContext()));

        mUsers = new ArrayList<>();

        readUsers();

        search_users = view.findViewById(R.id.search_users);
        search_users.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {

            }

            @Override
            public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
                searchUsers(charSequence.toString().toLowerCase());
            }

            @Override
            public void afterTextChanged(Editable editable) {

            }
        });

        return view;
    }

    private void searchUsers(String s) {

        final FirebaseUser fuser =FirebaseAuth.getInstance().getCurrentUser();

        Query query = FirebaseDatabase.getInstance().getReference("Users").orderByChild("search")
                .startAt(s)
                .endAt(s+"uf8ff");

        query.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                mUsers.clear();
                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                    User user = snapshot.getValue(User.class);

                    assert user != null;
                    assert fuser != null;
                    if (!user.getId().equals(fuser.getUid())) {
                        mUsers.add(user);
                    }
                }

                userAdapter = new UserAdapter(getContext(), mUsers, false);
                recyclerView.setAdapter(userAdapter);
            }

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

            }
        });

    }

    private void readUsers() {

        final FirebaseUser firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
        DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Users");

        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if (search_users.getText().toString().equals("")) {
                    mUsers.clear();
                    for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                        User user = snapshot.getValue(User.class);


                        assert user != null;
                        assert firebaseUser != null;  
                        if (!user.getId().equals(firebaseUser.getUid())) { //here
                            mUsers.add(user);
                        }
                    }

                    userAdapter = new UserAdapter(getContext(), mUsers, false);
                    recyclerView.setAdapter(userAdapter);
                }
            }

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

            }
        });
    }

}

Dependencies

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])

    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
//from here
    implementation 'com.google.firebase:firebase-analytics:17.2.2'
    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
    implementation 'com.google.android.material:material:1.1.0'

    implementation 'com.google.firebase:firebase-auth:19.2.0'
    implementation 'com.google.firebase:firebase-database:19.2.1'
    implementation 'androidx.cardview:cardview:1.0.0'
    implementation 'com.rengwuxian.materialedittext:library:2.1.4'
    implementation 'de.hdodenhof:circleimageview:3.1.0'
    implementation 'com.github.bumptech.glide:glide:4.11.0'

    implementation 'com.squareup.retrofit2:retrofit:2.7.1'
    implementation 'com.squareup.retrofit2:converter-gson:2.7.1'
    implementation 'com.google.firebase:firebase-messaging:20.1.0'

    implementation 'com.google.firebase:firebase-storage:19.1.1'
    implementation "androidx.fragment:fragment:1.2.1" // this shit
    implementation 'com.google.firebase:firebase-ads:18.3.0'

//to here
    testImplementation 'junit:junit:4.13'  //this was in .12
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
}