public void onDateSet(DatePicker view, int year, int month, int dayOfMonth) {
        date.set(year, month, dayOfMonth);
        DialogFragment timePickerFragment = new TimePickerFragment();
        timePickerFragment.show(getActivity().getSupportFragmentManager(), getString(R.string.timePicker));
    }

public class TimePickerFragment extends DialogFragment implements TimePickerDialog.OnTimeSetListener {
    private DateTimeSetter dateTimeSetter;
    private Calendar cal;
    private OnDateTimeListener callback;

    public void setOnDateTimeListener(OnDateTimeListener callback) {
        this.callback = callback;
    }
    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        cal = Calendar.getInstance();
        dateTimeSetter = new DateTimeSetter();
        dateTimeSetter.presetTime(cal);
    }
    @NonNull
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        return new TimePickerDialog(getActivity(), this, cal.get(Calendar.HOUR_OF_DAY), cal.get(Calendar.MINUTE), DateFormat.is24HourFormat(getActivity()));
    }
    @Override
    public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
        cal.set(Calendar.HOUR_OF_DAY, hourOfDay);
        cal.set(Calendar.MINUTE, minute);
        callback.OnDateTimeSet(hourOfDay, minute);
    }
    public interface OnDateTimeListener {
        void OnDateTimeSet(int hourOfDay, int minute);
    }
}

public class DatePickerFragment extends DialogFragment implements DatePickerDialog.OnDateSetListener {

    private Calendar date = Calendar.getInstance();

    @NonNull
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {

        return new DatePickerDialog(getActivity(), this, date.get(Calendar.YEAR), date.get(Calendar.MONTH), date.get(Calendar.DATE));
    }

    @Override
    public void onDateSet(DatePicker view, int year, int month, int dayOfMonth) {
        date.set(year, month, dayOfMonth);
        DialogFragment timePickerFragment = new TimePickerFragment();
        timePickerFragment.show(getActivity().getSupportFragmentManager(), getString(R.string.timePicker));
    }
}

public class NewTaskActivity extends AppCompatActivity implements TimePickerFragment.OnDateTimeListener {
..........
public void setCustomStartDateTime() {
        DialogFragment datePickerFragment = new DatePickerFragment();
        datePickerFragment.show(getSupportFragmentManager(), getString(R.string.datePicker));
    }

    @Override
    public void onAttachFragment(Fragment fragment) {
        if (fragment instanceof TimePickerFragment) {
            TimePickerFragment timePickerFragment = (TimePickerFragment) fragment;
            timePickerFragment.setOnDateTimeListener(this);
        }
    }

    @Override
    public void OnDateTimeSet(int hourOfDay, int minute) {
        startDateTextView.setText(dateFormatter.formatStartDate(cal));
    }
.....
}```