private static boolean checkNonBlankUsername(final Context context, final String username) {
        if (StringUtils.isBlank(username)) {
            ActivityMixin.showToast(context, R.string.warn_no_username);
            return false;
        }
        return true;
    }
Check if a given username is valid (non blank), and show a toast if it isn't.

@param context  an activity
@param username the username to check
@return <tt>true</tt> if the username is not blank, <tt>false</tt> otherwise
main/src/main/java/cgeo/geocaching/CacheListActivity.java