setText in NavDrawer Fragment from MainActivity - android-fragmentactivity

Question

I keep on getting this null object reference on setText method. Works fine with the navigation header but in the fragments it just keeps on crashing. I've tried making it this way or using Bundle to pass the strings and doesn't seem to be working.
How should I test it or what changes should I make?
public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {
private DrawerLayout drawer;
//NavHeader
private TextView header_name, header_email;
//SessionManager
SessionManager sessionManager;
//maps
private static final String TAG = "MainActivity";
private static final int ERROR_DIALOG_REQUEST = 9001;
private static final String FINELOCATION = Manifest.permission.ACCESS_FINE_LOCATION;
private static final String COURSELOCATION = Manifest.permission.ACCESS_COARSE_LOCATION;
private Boolean mLocationPermissionsGranted = false;
private static final int LOCATION_PERMISSION_REQUEST_CODE = 1234;
private static final float DEFAULT_ZOOM = 15f;
private FusedLocationProviderClient mFusedLocationProviderClient;
private GoogleMap mMap;
String pontopartida, pontochegada;
private EditText ponto_partidaInput, ponto_chegadaInput;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//GET USER DATA
sessionManager = new SessionManager(this);
sessionManager.checkLogin();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
View headerView = navigationView.getHeaderView(0);
header_name = (TextView) headerView.findViewById(R.id.header_name);
header_email = (TextView) headerView.findViewById(R.id.header_email);
HashMap<String, String> user = sessionManager.getUserDetail();
String mName = user.get(sessionManager.NAME);
String mEmail = user.get(sessionManager.EMAIL);
header_name.setText(mName);
header_email.setText(mEmail);
Log.d("Name: ", mName);
Log.d("Email: ", mEmail);
FragmentManager MyAccfrag = getSupportFragmentManager();
MyAccountFragment fragment = (MyAccountFragment) MyAccfrag.findFragmentById(R.id.nav_myaccount);
fragment.setText(mName, mEmail);
...
public class MyAccountFragment extends Fragment {
private TextView account_name;
private TextView account_email;
#Nullable
#Override
public View onCreateView(#NonNull LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_myaccount, container, false);
account_name = (TextView) view.findViewById(R.id.name_accountfrag);
account_email = (TextView) view.findViewById(R.id.email_accountfrag);
return view;
}
public void setText (String Name, String Email){
account_name.setText(Name);
account_email.setText(Email);
}
}