public void login(String email, String password) {
        mAuth.signInWithEmailAndPassword(email, password)
                .addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
                    @Override
                    public void onComplete(@NonNull Task<AuthResult> task) {
                        if (task.isSuccessful()) {
                            FirebaseUser user = mAuth.getCurrentUser();
                            Singleton.getInstance().setLoggedUser(new User(user.getUid(),user.getEmail()));

                            FirebaseDatabase.getInstance().getReference().child("memes")
                                    .addListenerForSingleValueEvent(new ValueEventListener() {
                                        @Override
                                        public void onDataChange(DataSnapshot dataSnapshot) {
                                            ArrayList<Meme> array = new ArrayList<>();

                                            for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                                                int id = Integer.parseInt(snapshot.getKey());
                                                String caption = snapshot.child("caption").getValue(String.class);
                                                int timesShared = Integer.parseInt(snapshot.child("timesShared").getValue(String.class));

                                                array.add(new Meme(id,caption,timesShared));
                                            }

                                            Singleton.getInstance().setMemeArray(array);
                                            //Log.d("tagprova",Singleton.getInstance().getMemeArray().toString());

                                            Intent i = new Intent(LoginActivity.this,HomeActivity.class);
                                            startActivity(i);
                                        }
                                        @Override
                                        public void onCancelled(DatabaseError databaseError) {
                                        }
                                    });

                        } else {
                            Log.d("tagprova", "signInWithEmail:failure", task.getException());
                            Toast.makeText(LoginActivity.this, "Login failed.", Toast.LENGTH_SHORT).show();
                        }
                    }
                });