AccountManager manager = AccountManager.get(context);
    Account[] accounts = manager.getAccountsByType("com.google");
    List<String> possibleEmails = new LinkedList<>();

    for (Account account : accounts) {
        possibleEmails.add(account.name);
    }

    if (!possibleEmails.isEmpty() && possibleEmails.get(0) != null) {
        String email = possibleEmails.get(0);
        String[] parts = email.split("@");

        if (parts.length > 1)
            return parts[0];
    }
    return null;