public static List<User> userList;
    private EditText editTextPhoneNumber;
    private EditText editTextPassword;
    private Button buttonLogIn;
    private DatabaseReference databaseUsers;

    public static List<User> listSameChildren;
    public static User currentUser;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_log_in);

        databaseUsers = FirebaseDatabase.getInstance().getReference("Users");

        userList = new ArrayList<>();

        editTextPhoneNumber = (EditText) findViewById(R.id.editTextPhone);
        editTextPassword = (EditText) findViewById(R.id.editTextPassword);
        buttonLogIn = (Button) findViewById(R.id.buttonLogIn);

        buttonLogIn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (credentialsFound())
                {
                    logIn();
                }
            }
        });

    }

    protected void onStart() {
        super.onStart();

        databaseUsers.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                userList.clear();
                for (DataSnapshot userSnapshot : dataSnapshot.getChildren()) {
                    User user = userSnapshot.getValue(User.class);
                    userList.add(user);
                    Log.i("YO", userList.get(0).getCredentials());
                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                Log.i("YO", "Failed to post");
            }

        });
    }

    private boolean credentialsFound()
    {
        String phoneNumber = editTextPhoneNumber.getText().toString().trim();
        String password = editTextPassword.getText().toString().trim();

        String familyKey;

        for (int i = 0; i < userList.size(); i++)
        {
            if (phoneNumber.equals(userList.get(i).getUserPhoneNumber()))
            {
                if (password.equals(userList.get(i).getUserPassword()))
                {
                    currentUser = userList.get(i);
                    familyKey = userList.get(i).getFamilyKey();
                    findChildrenOfFamily(familyKey);
                    return true;
                }
            }
        }
        Toast.makeText(this, "Enter the correct information!", Toast.LENGTH_LONG).show();
        return false;
    }

    private void logIn()
    {
        Toast.makeText(this, "It worked!", Toast.LENGTH_LONG).show();
        if (currentUser.isUserIsParent())
        {
            Intent intent = new Intent(this, ParentMainActivity.class);
            startActivity(intent);
        }
        else if (!currentUser.isUserIsParent())
        {
            Intent intent = new Intent(this, ChildMainActivity.class);
            startActivity(intent);
        }
    }

    private List<User> findChildrenOfFamily(String familyKey)
    {
        List<User> listSameFamily = new ArrayList<>();
        listSameChildren = new ArrayList<>();
        for (int i = 0; i < userList.size(); i++)
        {
            if (familyKey.equals(userList.get(i).getFamilyKey()))
            {
                listSameFamily.add(userList.get(i));
            }
        }

        for (int i = 0; i < listSameFamily.size(); i++)
        {
            if (!listSameFamily.get(i).isUserIsParent())
            {
                listSameChildren.add(listSameFamily.get(i));
            }
        }

        return listSameChildren;
    }