null for argument 'pathString'

Question

I am having an error when I perform queries in firebase, my code for query looks like this:

@Override
protected void onCreate(Bundle savedInstanceState) {
           


        

Answer 1

You're most likely getting an error because cpf is null when you use it as a child in mReferenceplaca. This happens because Firebase downloads data asynchronously and your code lines are executed synchronously. Therefore, by the time this line mReferencePlaca.child("Funcionario").child(cpf).child("placa") is executed, the value of cpf is still null because this cpf = dataSnapshot.getValue(String.class); hasn't happened yet.

To solve this, change this :-

    DatabaseReference mReferenceCpf = FirebaseDatabase.getInstance().getReference();
databaseReference.child("Usuario").child(uId).child("cnpjCpf")
        .addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
             cpf = dataSnapshot.getValue(String.class);
                txtCpf.setText(cpf);
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });



   DatabaseReference mReferencePlaca = FirebaseDatabase.getInstance().getReference();
    mReferencePlaca.child("Funcionario").child(cpf).child("placa")
            .addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    placa = dataSnapshot.getValue(String.class);
                    txtPlaca.setText(placa);
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });

to this :-

DatabaseReference mReferenceCpf = FirebaseDatabase.getInstance().getReference();
databaseReference.child("Usuario").child(uId).child("cnpjCpf")
        .addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
             cpf = dataSnapshot.getValue(String.class);
                txtCpf.setText(cps);

       DatabaseReference mReferencePlaca = FirebaseDatabase.getInstance().getReference();
        mReferencePlaca.child("Funcionario").child(cpf).child("placa")
                .addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        placa = dataSnapshot.getValue(String.class);
                        txtPlaca.setText(placa);
                    }

                    @Override
                    public void onCancelled(DatabaseError databaseError) {

                    }
                });
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });