checkValues

Checks whether given input string contains valid characters only.

Calls isNullOrBlank to check whether there are any letters or numbers in the given input String. Calls isAlphaNumeric to check whether only characters are in input string that are allowed: 'a' to 'z', 'A' to 'Z' and '0' to '9'. If the input provided by the user is blank or if it contains characters that are not allowed, an error will be shown in the corresponding edit text field to inform the user.