Android: How can I validate EditText input?


I need to do form input validation on a series of EditTexts. I'm using OnFocusChangeListeners to trigger the validation after the user types into each one, but this doesn't behave as desired for the last EditText.

If I click on the "Done" button while typing into the final EditText then the InputMethod is disconnected, but technically focus is never lost on the EditText (and so validation never occurs).

What's the best solution?

Should I be monitoring when the InputMethod unbinds from each EditText rather than when focus changes? If so, how?

5/4/2010 5:35:11 AM

Accepted Answer

Why don't you use TextWatcher ?

Since you have a number of EditText boxes to be validated, I think the following shall suit you :

  1. Your activity implements android.text.TextWatcher interface
  2. You add TextChanged listeners to you EditText boxes
  1. Of the overridden methods, you could use the afterTextChanged(Editable s) method as follows
public void afterTextChanged(Editable s) {
    // validation code goes here

The Editable s doesn't really help to find which EditText box's text is being changed. But you could directly check the contents of the EditText boxes like

String txt1String = txt1.getText().toString();
// Validate txt1String

in the same method. I hope I'm clear and if I am, it helps! :)

EDIT: For a cleaner approach refer to Christopher Perry's answer below.

5/23/2017 11:47:18 AM

If you want nice validation popups and images when an error occurs you can use the setError method of the EditText class as I describe here

Screenshot of the use of setError taken from Donn Felker, the author of the linked post


In order to reduce the verbosity of the validation logic I have authored a library for Android. It takes care of most of the day to day validations using Annotations and built-in rules. There are constraints such as @TextRule, @NumberRule, @Required, @Regex, @Email, @IpAddress, @Password, etc.,

You can add these annotations to your UI widget references and perform validations. It also allows you to perform validations asynchronously which is ideal for situations such as checking for unique username from a remote server.

There is a example on the project home page on how to use annotations. You can also read the associated blog post where I have written sample codes on how to write custom rules for validations.

Here is a simple example that depicts the usage of the library.

@Required(order = 1)
@Email(order = 2)
private EditText emailEditText;

@Password(order = 3)
@TextRule(order = 4, minLength = 6, message = "Enter at least 6 characters.")
private EditText passwordEditText;

@ConfirmPassword(order = 5)
private EditText confirmPasswordEditText;

@Checked(order = 6, message = "You must agree to the terms.")
private CheckBox iAgreeCheckBox;

The library is extendable, you can write your own rules by extending the Rule class.


This was nice solution from here

InputFilter filter= new InputFilter() { 
    public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) { 
        for (int i = start; i < end; i++) { 
            String checkMe = String.valueOf(source.charAt(i));

            Pattern pattern = Pattern.compile("[ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz123456789_]*");
            Matcher matcher = pattern.matcher(checkMe);
            boolean valid = matcher.matches();
                Log.d("", "invalid");
                return "";
        return null; 

edit.setFilters(new InputFilter[]{filter}); 

Updated approach - TextInputLayout:

Google has recently launched design support library and there is one component called TextInputLayout and it supports showing an error via setErrorEnabled(boolean) and setError(CharSequence).

How to use it?

Step 1: Wrap your EditText with TextInputLayout:


      android:id="@+id/editText1" />


Step 2: Validate input

// validating input on a button click
public void btnValidateInputClick(View view) {

    final TextInputLayout layoutUserName = (TextInputLayout) findViewById(;
    String strUsername = layoutLastName.getEditText().getText().toString();

    if(!TextUtils.isEmpty(strLastName)) {
        Snackbar.make(view, strUsername, Snackbar.LENGTH_SHORT).show();
    } else {
        layoutUserName.setError("Input required");

I have created an example over my Github repository, checkout the example if you wish to!


I wrote a class that extends EditText which supports natively some validation methods and is actually very flexible.

Current, as I write, natively supported through xml attributes validation methods are:

  1. alpha
  2. alpha numeric
  3. numeric
  4. generic regexp
  5. string emptyness

You can check it out here

Hope you enjoy it :)


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