Fragments Android Studio

Good afternoon,

I am not able to recover the data from the fragments by pressing the back button.

My bandle is ok, the result appears normally, but when it comes back to the cpf screen the value is not applied

I'm trying to create a registration form in stages, each fragment is a field to be written

//fragment Email
btnBack.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        bundle = new Bundle();
        bundle.putSerializable("object", user);
        Log.i("Bundle", bundle.toString());
        Navigation.findNavController(v).navigate(R.id.cpfFragment, bundle);
    }
});

fragment that I can't recover the data

public class CpfFragment extends Fragment {

    private User user;
    private Bundle bundle;

    public CpfFragment() {
        // Required empty public constructor
    }

    @Override
    public void onStart() {
        super.onStart();
    }

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

        if(savedInstanceState != null){
            user = (User) bundle.getSerializable("object");
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_cpf, container, false);
    }

    @Override
    public void onViewCreated(@NonNull final View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        Button btnNext = view.findViewById(R.id.btnNext);
        Button btnBack = view.findViewById(R.id.btnBack);

        final EditText fieldCpf = view.findViewById(R.id.editCpf);


        btnProximo.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String cpf = fieldCpf.getText().toString();

                try {
                    if (cpf.isEmpty()){
                        Toast.makeText(getContext(), "Preencha o Cpf para avançar", Toast.LENGTH_SHORT).show();
                    }
                    else{

                        user = new Usuario();
                        user.setCpf(cpf);
                        Log.i("CPF", user.getCpf());

                        bundle = new Bundle();
                        bundle.putSerializable("object", user);

                        Navigation.findNavController(v).navigate(R.id.emailFragment, bundle);
                    }
                }
                catch (Exception e ){
                    Toast.makeText(getContext(), e.getMessage(), Toast.LENGTH_SHORT).show();
                    Log.i("ERROR BAGME CPF", e.getMessage());
                }
            }
        });

        btnVoltar.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Navigation.findNavController(v).navigate(R.id.initialFragment);
            }
        });
    }
}

You don't return data over bundles. Create a interface in your fragment implement it in your activity and save your activity as said interface in the onAttach method. Then let the activity handle all stuff like saving the data and showing the next fragment.

More info and source: https://developer.android.com/guide/components/fragments#EventCallbacks

You can make a singleton class and save the values using getter and setter.