App Crashes when enter OnDataChange FireBase Android

Question

I'm getting an error when I try to Cast A DataSnapshot as a Hashmap.

private void ponerCasoEnLista(){



        final ArrayList<DatosCaso> datos = new ArrayList<>();
        RUTA_DB.child("casos").addValueEventListener(new ValueEventListener() {

            @Override
            public void onDataChange(DataSnapshot snapshot) {
                HashMap<String, String> casos = (HashMap<String, String>) snapshot.getValue();
                for (Object caso : casos.values()) {
                    HashMap<String, Object> casoMap = (HashMap<String, Object>) caso;
                    DatosCaso nuevosdatos = new DatosCaso((String) casoMap.get("nombre"), (String) casoMap.get("color"));
                    datos.add(nuevosdatos);
                    Log.d("NUEVOCASO", "Agrego caso al array");

                   /* if (!userInfoList.contains(userNumber)) {
                        String name = (String) userMap.remove("username");
                        String pic = (String) userMap.remove("profile_picture");
                        UserInfo info = new UserInfo(userNumber, name, pic);
                        userInfoList.add(info);
                    }*/
                }
                // thread executing here can get info from database and make subsequent call
                Collections.addAll(datos);
                ponerCasoEnListview(datos);
            }

I'm getting this:

10-16 00:30:22.951 15066-15066/? E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.example.gasti.escribocaso1510, PID: 15066 java.lang.ClassCastException: java.lang.Long cannot be cast to java.util.HashMap at com.example.gasti.escribocaso1510.ActividadPrincipal$2.onDataChange(ActividadPrincipal.java:109)

In this line after OnDataChange:

HashMap<String, String> casos = (HashMap<String, String>) snapshot.getValue();

Answer 1

To cast to a HashMap, simply use

        @Override
        public void onDataChange(DataSnapshot dataSnapshot)
        {   Map<String, Object> objectMap = (HashMap<String, Object>) dataSnapshot.getValue();
            Log.e("***", "onDataChange -> " + objectMap.toString());
        }

Answer 2

It is impossible to be sure without seeing your data structure, but I'm guessing that casos is a list of multiple caso objects.

In that case:

public void onDataChange(DataSnapshot snapshot) {
    for (Object caso : casos.values()) {
        HashMap<String, Object> casoMap = (HashMap<String, Object>) caso;
        DatosCaso nuevosdatos = new DatosCaso((String) casoMap.get("nombre"), (String) casoMap.get("color"));

You should seriously consider creating a JavaBean object for DatosCaso:

public class DatosCaso {
  String nombre;
  String color;
  public DatosCaso() {}
  public String getNombre() { return nombre; }
  public String getColor() { return color; }
}

This allows you to bypass the HashMap:

DatosCaso nuevosdatos = caso.getValue(DatosCaso.class);