Form validation for Android
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About AValidation

AValidation is a validation framework for Android. AValidation is an easy way to validate an EditText when the content changes. An error icon and optional message will be displayed if there is a validation error.

It can also compare the content of an EditText with content of another EditText when validating (see ComparingMaxIntegerValidator).

The same validators can also be used to validate the entire form.

Start with the "Getting started" guide and then check out the Javadoc.

Getting started with AValidation

This is a guide to describe how to use AValidation when developing an Android application. The example use a simple StringValidator. See "Different Validators" for other validators or "Create a Custom Validator" to create your own Validator.

Step 1: Downloading

Click here to download the AValidation jar.

Step 2: Add AValidation to your project

Put the downloaded jar file in the "libs" directory of the android project.

Step 3: Create a Validator

This example validates that a string has a max length of 10 characters.

StringValidator commentsValidator = new StringValidator(0, 10, null, resources.getString(R.string.comment_error_max_length));

Step 4: Add the Validator to an EditText

EditText editTextComment = (EditText) findViewById(;
ValidationUtil.validateOnChange(editTextComment, commentsValidator);

Available Validators

Table of Contents


Check that a string is not empty.

new RequiredValidator(resources.getString(R.string.required_error));


Validates that a string is between a min and max length.

new StringValidator(0, 10, null, resources.getString(R.string.error_max_length));





Create a custom Validator

Create a custom validator by implementing the Validator interface. Override the validate method and return null on successful validation or a String on validation error.

This example shows how the RequiredValidator is implemented.


import android.text.TextUtils;

 * Validates that a String is not empty.
 * @author Jon Wikman
public class RequiredValidator implements Validator {
    private String requiredError;

     * Creates a new RequiredValidator.
    public RequiredValidator(String requiredError) {
        this.requiredError = requiredError;

     * Validates that a String is not empty.
     * @param value
     *            The String to validate.
     * @return The error message if value is empty otherwise null.
    public String validate(String value) {
        return TextUtils.isEmpty(value) ? requiredError : null;