Implementing an activity inside a fragment in android studio

I'm trying to make an app in android studio that has different tabs using fragments. I want one of these tabs to show a calendar so that when that fragment is opened (using a navigation bar), the calendar appears.

I'm having trouble integrating my calendar activity into the fragment activity file. I'm also new to android studio so I'm a bit lost on what to do.

CalendarActivity:

public class CalendarActivity extends AppCompatActivity implements CalendarAdapter.OnItemListener{
    private TextView monthYearText;
    private RecyclerView calendarRecyclerView;
    private LocalDate selectedDate;

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_calendar);
        initWidgets();
        selectedDate = LocalDate.now();
        setMonthView();

        // new
        CalendarFragment calendarFragment = new CalendarFragment();
        getSupportFragmentManager().beginTransaction().add(R.id.bottomNavigationView, calendarFragment).commit();
    }

    private void initWidgets(){
        calendarRecyclerView = findViewById(R.id.calendarRecyclerView);
        monthYearText = findViewById(R.id.monthYearTV);
    }

    private void setMonthView(){
        monthYearText.setText(monthYearFromDate(selectedDate));
        ArrayList<String> daysInMonth = daysInMonthArray(selectedDate);

        CalendarAdapter calendarAdapter = new CalendarAdapter(daysInMonth, this);
        RecyclerView.LayoutManager layoutManager = new GridLayoutManager(getApplicationContext(), 7);
        calendarRecyclerView.setLayoutManager(layoutManager);
        calendarRecyclerView.setAdapter(calendarAdapter);
    }

    private ArrayList<String> daysInMonthArray(LocalDate date){
        ArrayList<String> daysInMonthArray = new ArrayList<>();
        YearMonth yearMonth = YearMonth.from(date);

        int daysInMonth = yearMonth.lengthOfMonth();

        LocalDate firstOfMonth = selectedDate.withDayOfMonth(1);
        int dayOfWeek = firstOfMonth.getDayOfWeek().getValue();

        for(int i = 1; i <= 42; i++){
            if(i <= dayOfWeek || i > daysInMonth + dayOfWeek){
                daysInMonthArray.add("");
            }
            else{
                daysInMonthArray.add(String.valueOf(i - dayOfWeek));
            }
        }
        return  daysInMonthArray;
    }

    @Override
    public void onItemClick(int position, String dayText){
        if(!dayText.equals(""))
        {
            String message = "Selected Date " + dayText + " " + monthYearFromDate(selectedDate);
            Toast.makeText(this, message, Toast.LENGTH_LONG).show();
        }
    }
}

CalendarFragment:

public class CalendarFragment extends Fragment{

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_calendar, container, false);
    }
}

MainActivity:

public class MainActivity extends AppCompatActivity {

    ActivityMainBinding binding;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        binding = ActivityMainBinding.inflate(getLayoutInflater());
        setContentView(binding.getRoot());
        replaceFragment(new HomeFragment());

        // making home the default highlighted item
        BottomNavigationView mBottomNavigationView=(BottomNavigationView)findViewById(R.id.bottomNavigationView);
        mBottomNavigationView.getMenu().findItem(R.id.home).setChecked(true);

        binding.bottomNavigationView.setOnItemSelectedListener(item -> {
            switch (item.getItemId()){
                case R.id.home:
                    replaceFragment(new HomeFragment());
                    break;

                case R.id.scan:
                    replaceFragment(new ScanFragment());
                    break;

                case R.id.calendar:
                    replaceFragment(new CalendarFragment());
                    break;}
            return true;
        }); }

     private void replaceFragment (Fragment fragment){
         FragmentManager fragmentManager = getSupportFragmentManager();
         FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
         fragmentTransaction.replace(R.id.frame_layout, fragment);
         fragmentTransaction.commit();
     }}