什么是不可及陈述。我不能使用firebasefirestore，而且方法在片段视图中是不可访问的语句。如何使用方法和其他东西以及什么是不可达语句？

private FragmentPostfragBinding binding;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        binding=FragmentPostfragBinding.inflate(inflater,container,false);
        View view=binding.getRoot();
        return view;

        userview();

    }

    private void userview() {
        FirebaseFirestore db;

        db=FirebaseFirestore.getInstance();
        DocumentReference ref = db.collection("user").document(FirebaseAuth.getInstance().getCurrentUser().getUid());
        ref.get()
                .addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>(){
                    @Override
                    public void onSuccess(DocumentSnapshot documentSnapshot) {
                        if(documentSnapshot.exists()){

                            String name=documentSnapshot.getString("username");
                            binding.user.setText(name);

                        }
                        else{
                            Toast.makeText(getActivity(), "Sorry, your information is not saved!", Toast.LENGTH_SHORT).show();
                            Intent intent=new Intent(getActivity(),otherinfo.class);
                            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_CLEAR_TOP);
                            startActivity(intent);
                        }
                    }
                })
                .addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Toast.makeText(getActivity(), "Error!", Toast.LENGTH_SHORT).show();
                        Log.i(TAG, "onFailure: "+e.toString());
                    }
                });
    }
}