ChatsActivity.java

package change.com.animationwithsplash;

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.ImageView;
import android.widget.TextView;

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 change.com.animationwithsplash.Fragments.ChatsFragment;
import change.com.animationwithsplash.Fragments.ProfileFragment;
import change.com.animationwithsplash.Fragments.UsersFragment;
import change.com.animationwithsplash.Models.User;

public class ChatsActivity extends AppCompatActivity {
    ImageView Profile_Image;
    TextView Username;

    FirebaseUser firebaseUser;
    DatabaseReference reference;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_chats);

        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());
                Profile_Image.setImageResource(R.drawable.ic_account3);
            }

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

            }
        });
        TabLayout tabLayout = findViewById(R.id.tab_layout);
        ViewPager viewPager = findViewById(R.id.view_pager);
        ViewPageAdapter viewPageAdapter = new ViewPageAdapter(getSupportFragmentManager());
        viewPageAdapter.addFragment(new ChatsFragment(),"Chats");
        viewPageAdapter.addFragment(new UsersFragment(),"Users");
        viewPageAdapter.addFragment(new ProfileFragment(),"Profile");

        viewPager.setAdapter(viewPageAdapter);
        tabLayout.setupWithViewPager(viewPager);
    }
    @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(ChatsActivity.this,Login.class));
                finish();
                return true;
        }
        return false;
    }
    class ViewPageAdapter extends FragmentPagerAdapter
    {
        private ArrayList<Fragment> fragments;
        private ArrayList<String> titles;

        ViewPageAdapter(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);
        }
    }
}