Android simple user input validation system, with support for EditText, AutoCompleteTextView, TextInputLayout

ProfileActivity.java

/**
 * The activity containing your EditTexts.
 */
public class ProfileActivity extends AppCompatActivity {
  
    /**
     * Input field "your name".
     */
    @Bind(R.id.edittext_name)
    EditText nameEditText;

    /**
     * Input field "mobile number".
     */
    @Bind(R.id.edittext_mobile_number)
    EditText mobileNumberEditText;
    
    /**
     * Activity-specific user input validator.
     */
    ProfileInputValidator inputValidator;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_profile);
        ButterKnife.bind(this);
    }
    
    /**
     * Action when the "validate" button is pressed.
     */
    @OnClick(R.id.button_profile_validate)
    public void validateButtonClick() {
        if (getInputValidator().validateUserInput()) {
            // The EditTexts are filled as wanted
        }
    }
    
    
    // --------------------------- VALIDATOR PART ---------------------------
    
    /**
     * Custom validator definition.
     */
    public class ProfileInputValidator extends UserInputValidator {
        @Override
        protected void buildRules() {
            // Build a rule for each EditText, specifying the wanted format and error message
            rulesMap.put(nameEditText, new Rule(Consts.REGEX_USERNAME, getString(R.string.profile_error_name)));
            rulesMap.put(mobileNumberEditText, new Rule(Consts.REGEX_MOBILE, getString(R.string.profile_error_mobile)));
        }
    }

    public ProfileInputValidator getInputValidator() {
        if (inputValidator == null) {
            inputValidator = new ProfileInputValidator();
        }

        return inputValidator;
    }
    
}

UserInputValidator.java

/**
 * Abstract class containing common validation functionalitites.
 */
public abstract class UserInputValidator {

    /**
     * Set containing all the EditTexts in error.
     */
    protected Set<EditText> viewsInError;

    /**
     * All the validation rules associated to a field.
     */
    protected Map<EditText, Rule> rulesMap;

    public Set<EditText> getViewsInError() {
        return viewsInError;
    }

    /**
     * Default constructor, building validation rules.
     */
    protected UserInputValidator() {
        viewsInError = new HashSet<>();
        rulesMap = new HashMap<>();

        buildRules();
    }

    /**
     * Build validation rules on the fields.
     */
    protected abstract void buildRules();

    /**
     * Verify that the user input is valid.
     *
     * @return True if the input is correct.
     */
    public boolean validateUserInput() {
        for (Map.Entry<EditText, Rule> rule : rulesMap.entrySet()) {
            EditText editText = rule.getKey();
            Rule validationRule = rule.getValue();

            boolean isInputValid = editText.getText() != null && editText.getText().toString().matches(validationRule.regExFormat);

            ViewParent parent = editText.getParent();
            TextInputLayout parentLayout = null;
            String errorMessage;
            if(parent instanceof TextInputLayout) {
                parentLayout = (TextInputLayout) parent;
            }

            if(isInputValid) {
                viewsInError.remove(editText);
                errorMessage = null;
            } else {
                viewsInError.add(editText);
                errorMessage = validationRule.errorMessage;
            }

            if(parentLayout != null) {
                parentLayout.setError(errorMessage);
            } else {
                editText.setError(errorMessage);
            }
        }

        return viewsInError.isEmpty();
    }

    /**
     * A validation rule (wanted format, error message).
     */
    protected static class Rule {

        /**
         * Wanted format expressed as a RegEx.
         */
        final String regExFormat;

        /**
         * The error message shown if the input doesn't match.
         */
        final String errorMessage;

        public Rule(String regExFormat, String errorMessage) {
            this.regExFormat = regExFormat;
            this.errorMessage = errorMessage;
        }
    }
}