Android / Firebase - NullPointerException when defining Query object

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Android / Firebase - NullPointerException when defining Query object

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#1 by (1 votes)

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Hello,
I have a problem reading the data in Firebase. I use Android Studio 3.0 and Java. I can connect to the database, get the instance, the user logged in, but I can not read the attributes of the selected node.

The bank structure is this here:

{
  "user" : {
    "YWxsYW5AbmVyb3MuY29tLmJy" : {
      "active" : true,
      "id" : "YWxsYW5AbmVyb3MuY29tLmJy",
      "userEmail" : "[email protected]",
      "userName" : "Allan Neros",
    }
  }
}

What I want is to get all the children of the "YWxsYW5AbmVyb3MuY29tLmJy" node.

The Java code I wrote to solve is this one:

    FirebaseDatabase dbsFirebase = FirebaseDatabase.getInstance();
    DatabaseReference refFirebase  = dbsFirebase.getReference();
    System.out.println("Reference: " + refFirebase.toString());

    //strUserId é uma String que retorna o id do nó, e está funcionando corretamente
    Query mQuery = refFirebase.child("user").orderByChild("id").equalTo(strUserId).limitToFirst(1);
    System.out.println("Query: " + mQuery.getRef().getKey());

    //A aplicação encerra nesta linha, nem passa pelo onDataChange
    mQuery.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            loggedUser = new User();
            //User loggedUser = dataSnapshot.getValue(User.class);
            loggedUser.setId(dataSnapshot.child("id").getValue().toString());
            loggedUser.setUserName(dataSnapshot.child("userName").getValue().toString());
            loggedUser.setUserEmail(dataSnapshot.child("userEmail").getValue().toString());
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            System.out.println("Erro: " + databaseError.getDetails());
        }
    });

The User class has the same attributes as the bank.

After these codes, I'm defining the Activity TextViews with the loggedUser information, but since it's empty, I get a NullPointerException (which makes sense, because the loggedUser object is not being created because it does not go into the onDataChange) . I built the code with what I found in the Firebase documentation and in examples collected on the internet (including posts here from StackOverflow).

Any clue why this error is happening? Is there a better way to get this information?

Thank you for your attention and help.

java android firebase

asked by anonymous 31.10.2017 / 17:09

1 answer

I am not able to load the image that demonstrates error using jQuery Routine to download and unzip zip file on the server itself

score 1 · Accepted Answer

If you want to catch all the child's reference "YWxsYW5AbmVyb3MuY29tLmJy", point the reference itself to this Key, and then add an event listener directly in the reference

refFirebase.child("users").child(strUserId);
refFirebase.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            //Supondo que aqui a classe é igual ao seu nó no Firebase
            User loggedUser = dataSnapshot.getValue(User.class);

            //Executa o que precisar com o loggedUser aqui.
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            System.out.println("Erro: " + databaseError.getDetails());
        }
    });