How to Iterate on Datasnapshot correctly in Firebase?

Question

I am 8 days trying to get from firebase the records I put there. However, I can never bring them properly.

--- Android for Firebase

   private void initPreencheLista() {
        listCelula.clear();
        novaRef = databaseReference.child( "Celulas" );
        novaRef.addValueEventListener( new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                Celula c = new Celula();
                for(DataSnapshot objSnapshot:dataSnapshot.getChildren()){
                    c = objSnapshot.getValue(Celula.class);
                    cels.add( c.getCelula() );
                }
                arrayAdapterCelula = new ArrayAdapter<String>(CelulasActivity.this,android.R.layout.simple_list_item_1, cels );
                celulaList.setAdapter( arrayAdapterCelula );
            }

I tried so many ways to do that I even used

   for(DataSnapshot objSnapshot:dataSnapshot.getChildren()){
                 String a = objSnapshot.child( "Celula" ).getValue(String.class);
                 cels.add( a );

I just can’t give up. I’m in the fight, if anyone can help me I’ll be grateful.

In the first way the objSnapshot comes loaded with all the object I called. Error: com.google.firebase.database.Databaseexception: Can’t Convert Object of type java.lang.String to type cellulae.Cellula.

Answer 1

How is your node arranged in firebase? For example, if your node is with two keys you will need to traverse the data with two for. One for the first key and one for the second key. Something like this:

public void onDataChange(@NonNull DataSnapshot dataSnapshot) {                
                Log.i("retorno", dataSnapshot.getValue().toString());
                //Estrutura: Id1, Id2, então são 2 for.

                for (DataSnapshot ds : dataSnapshot.getChildren()) {
                    for(DataSnapshot dados : ds.getChildren()){
                        Usuario user = dados.getValue(Usuario.class);
                        idUsuario = usuario.getIdUsuario();                           
                        Log.i("Escolhido", "Id: " + idUsuario);

                    }
                }