TextInputLayout Form Validation Using Data Binding in Android

Afew days ago, I was working on a project where I had to implement form validation on textInputLayout and textInputEditText using data binding.
Unfortunately, there is not enough documentation available for that.

Finally, I achieved what I wanted through some research and experiments. This is what I wanted to achieve:

So I know there are many developers who want the same actions and user-friendly behaviour on forms.

Let’s get started.

What Are We Going to Use?

• Kotlin
• Data binding
• Material library

I am going to break the whole project down into steps to make it easy for you to understand.

Set up the initial project and enable data-binding from build.gradle(:app) by adding this line under the android{} tag:

dataBinding{
    enabled true
}

To use textInputLayout and textInputEditText, you need to enable Material support for Android by adding this dependency in build.gradle(:app):

implementation 'com.google.android.material:material:1.2.1'

Let’s make a layout of our form. I am making it simple because my goal is to define the core functional part of this feature rather than designing the layout.

Roadmap to Becoming a Successful Android Developer

I made this simple layout:

Here is the activity_main.xml:

	<?xml version="1.0" encoding="utf-8"?>
	<layout xmlns:android="http://schemas.android.com/apk/res/android"
	xmlns:app="http://schemas.android.com/apk/res-auto"
	xmlns:tools="http://schemas.android.com/tools">
	<LinearLayout
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	android:layout_margin="10dp"
	android:orientation="vertical"
	tools:context=".MainActivity">
	<com.google.android.material.textfield.TextInputLayout
	android:id="@+id/userNameTextInputLayout"
	style="@style/TextInputLayoutBoxColor"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:layout_marginTop="10dp"
	android:hint="@string/username"
	app:endIconMode="clear_text"
	app:errorEnabled="true"
	app:hintTextAppearance="@style/TextAppearance.App.TextInputLayout">
	<com.google.android.material.textfield.TextInputEditText
	android:id="@+id/userName"
	android:layout_width="match_parent"
	android:layout_height="50dp"
	android:inputType="textPersonName" />
	</com.google.android.material.textfield.TextInputLayout>
	<com.google.android.material.textfield.TextInputLayout
	android:id="@+id/emailTextInputLayout"
	style="@style/TextInputLayoutBoxColor"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:layout_marginTop="5dp"
	android:hint="@string/email"
	app:endIconMode="clear_text"
	app:errorEnabled="true"
	app:hintTextAppearance="@style/TextAppearance.App.TextInputLayout">
	<com.google.android.material.textfield.TextInputEditText
	android:id="@+id/email"
	android:layout_width="match_parent"
	android:layout_height="50dp"
	android:inputType="textEmailAddress" />
	</com.google.android.material.textfield.TextInputLayout>
	<com.google.android.material.textfield.TextInputLayout
	android:id="@+id/passwordTextInputLayout"
	style="@style/TextInputLayoutBoxColor"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:layout_marginTop="5dp"
	android:hint="@string/password"
	app:errorEnabled="true"
	app:hintTextAppearance="@style/TextAppearance.App.TextInputLayout"
	app:passwordToggleEnabled="true">
	<com.google.android.material.textfield.TextInputEditText
	android:id="@+id/password"
	android:layout_width="match_parent"
	android:layout_height="50dp"
	android:inputType="textPassword" />
	</com.google.android.material.textfield.TextInputLayout>
	<com.google.android.material.textfield.TextInputLayout
	android:id="@+id/confirmPasswordTextInputLayout"
	style="@style/TextInputLayoutBoxColor"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:layout_marginTop="5dp"
	android:hint="@string/confirm_password"
	app:errorEnabled="true"
	app:hintTextAppearance="@style/TextAppearance.App.TextInputLayout"
	app:passwordToggleEnabled="true">
	<com.google.android.material.textfield.TextInputEditText
	android:id="@+id/confirmPassword"
	android:layout_width="match_parent"
	android:layout_height="50dp"
	android:inputType="textPassword"
	app:passwordToggleEnabled="true" />
	</com.google.android.material.textfield.TextInputLayout>
	<com.google.android.material.button.MaterialButton
	android:id="@+id/loginButton"
	android:layout_width="match_parent"
	android:layout_height="wrap_content"
	android:text="@string/login"
	android:textAllCaps="false" />
	</LinearLayout>
	</layout>

view raw activity_main.xml hosted with ❤ by GitHub

Our layout is ready. Let’s do some coding now.

If you look at the GIF of the final app (earlier in the article), you will see how errors are showing and hiding accordingly as the conditions become true.

This is because I have bound each text field with TextWatcher, which continuously calls as a user types something in the field.

Here, I have made a class inside MainActivity.kt that inherits from TextWatcher:

	/**
	* applying text watcher on each text field
	*/
	inner class TextFieldValidation(private val view: View) : TextWatcher {
	override fun afterTextChanged(s: Editable?) {}
	override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {}
	override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
	// checking ids of each text field and applying functions accordingly.
	}
	}

view raw MainActivity.java hosted with ❤ by GitHub

Don’t worry about view, which is passing in the constructor of the class. I will define it later.

Here is the main part. Each text field has some conditions that need to be true before submitting the form. So, the code for each text field condition is as follows:

	/**
	* field must not be empy
	*/
	private fun validateUserName(): Boolean {
	if (binding.userName.text.toString().trim().isEmpty()) {
	binding.userNameTextInputLayout.error = "Required Field!"
	binding.userName.requestFocus()
	return false
	} else {
	binding.userNameTextInputLayout.isErrorEnabled = false
	}
	return true
	}
	/**
	* 1) field must not be empty
	* 2) text should matches email address format
	*/
	private fun validateEmail(): Boolean {
	if (binding.email.text.toString().trim().isEmpty()) {
	binding.emailTextInputLayout.error = "Required Field!"
	binding.email.requestFocus()
	return false
	} else if (!isValidEmail(binding.email.text.toString())) {
	binding.emailTextInputLayout.error = "Invalid Email!"
	binding.email.requestFocus()
	return false
	} else {
	binding.emailTextInputLayout.isErrorEnabled = false
	}
	return true
	}
	/**
	* 1) field must not be empty
	* 2) password lenght must not be less than 6
	* 3) password must contain at least one digit
	* 4) password must contain atleast one upper and one lower case letter
	* 5) password must contain atleast one special character.
	*/
	private fun validatePassword(): Boolean {
	if (binding.password.text.toString().trim().isEmpty()) {
	binding.passwordTextInputLayout.error = "Required Field!"
	binding.password.requestFocus()
	return false
	} else if (binding.password.text.toString().length < 6) {
	binding.passwordTextInputLayout.error = "password can't be less than 6"
	binding.password.requestFocus()
	return false
	} else if (!isStringContainNumber(binding.password.text.toString())) {
	binding.passwordTextInputLayout.error = "Required at least 1 digit"
	binding.password.requestFocus()
	return false
	} else if (!isStringLowerAndUpperCase(binding.password.text.toString())) {
	binding.passwordTextInputLayout.error =
	"Password must contain upper and lower case letters"
	binding.password.requestFocus()
	return false
	} else if (!isStringContainSpecialCharacter(binding.password.text.toString())) {
	binding.passwordTextInputLayout.error = "1 special character required"
	binding.password.requestFocus()
	return false
	} else {
	binding.passwordTextInputLayout.isErrorEnabled = false
	}
	return true
	}
	/**
	* 1) field must not be empty
	* 2) password and confirm password should be same
	*/
	private fun validateConfirmPassword(): Boolean {
	when {
	binding.confirmPassword.text.toString().trim().isEmpty() -> {
	binding.confirmPasswordTextInputLayout.error = "Required Field!"
	binding.confirmPassword.requestFocus()
	return false
	}
	binding.confirmPassword.text.toString() != binding.password.text.toString() -> {
	binding.confirmPasswordTextInputLayout.error = "Passwords don't match"
	binding.confirmPassword.requestFocus()
	return false
	}
	else -> {
	binding.confirmPasswordTextInputLayout.isErrorEnabled = false
	}
	}
	return true
	}

view raw MainActivity.kt hosted with ❤ by GitHub

Now it’s time to bind each text field with the textWatcher class that we created earlier:

	private fun setupListeners() {
	binding.userName.addTextChangedListener(TextFieldValidation(binding.userName))
	binding.email.addTextChangedListener(TextFieldValidation(binding.email))
	binding.password.addTextChangedListener(TextFieldValidation(binding.password))
	binding.confirmPassword.addTextChangedListener(TextFieldValidation(binding.confirmPassword))
	}

view raw MainActivity.kt hosted with ❤ by GitHub

But how would TextFieldValidation know which text field to bind? Scroll up and have a look at the comment that I have mentioned inside the TextFieldValidation method:

// checking ids of each text field and applying functions accordingly.

Notice I am passing a view inside the constructor of TextFieldValidation, the class that is responsible for segregating each text field and applying each of the methods above like this:

	/**
	* applying text watcher on each text field
	*/
	inner class TextFieldValidation(private val view: View) : TextWatcher {
	override fun afterTextChanged(s: Editable?) {}
	override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {}
	override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
	// checking ids of each text field and applying functions accordingly.
	when (view.id) {
	R.id.userName -> {
	validateUserName()
	}
	R.id.email -> {
	validateEmail()
	}
	R.id.password -> {
	validatePassword()
	}
	R.id.confirmPassword -> {
	validateConfirmPassword()
	}
	}
	}
	}

view raw MainActivity.kt hosted with ❤ by GitHub

Your final MainActivity.kt would look like this:

	package com.example.textinputlayoutformvalidation
	import androidx.appcompat.app.AppCompatActivity
	import android.os.Bundle
	import android.text.Editable
	import android.text.TextWatcher
	import android.util.Patterns
	import android.view.View
	import android.widget.Toast
	import androidx.databinding.DataBindingUtil
	import com.example.textinputlayoutformvalidation.FieldValidators.isStringContainNumber
	import com.example.textinputlayoutformvalidation.FieldValidators.isStringContainSpecialCharacter
	import com.example.textinputlayoutformvalidation.FieldValidators.isStringLowerAndUpperCase
	import com.example.textinputlayoutformvalidation.FieldValidators.isValidEmail
	import com.example.textinputlayoutformvalidation.databinding.ActivityMainBinding
	/**
	* created by : Mustufa Ansari
	* Email : [e-mail]
	*/
	class MainActivity : AppCompatActivity() {
	lateinit var binding: ActivityMainBinding
	override fun onCreate(savedInstanceState: Bundle?) {
	super.onCreate(savedInstanceState)
	binding = DataBindingUtil.setContentView(this, R.layout.activity_main)
	setupListeners()
	binding.loginButton.setOnClickListener {
	if (isValidate()) {
	Toast.makeText(this, "validated", Toast.LENGTH_SHORT).show()
	}
	}
	}
	private fun isValidate(): Boolean =
	validateUserName() && validateEmail() && validatePassword() && validateConfirmPassword()
	private fun setupListeners() {
	binding.userName.addTextChangedListener(TextFieldValidation(binding.userName))
	binding.email.addTextChangedListener(TextFieldValidation(binding.email))
	binding.password.addTextChangedListener(TextFieldValidation(binding.password))
	binding.confirmPassword.addTextChangedListener(TextFieldValidation(binding.confirmPassword))
	}
	/**
	* field must not be empy
	*/
	private fun validateUserName(): Boolean {
	if (binding.userName.text.toString().trim().isEmpty()) {
	binding.userNameTextInputLayout.error = "Required Field!"
	binding.userName.requestFocus()
	return false
	} else {
	binding.userNameTextInputLayout.isErrorEnabled = false
	}
	return true
	}
	/**
	* 1) field must not be empty
	* 2) text should matches email address format
	*/
	private fun validateEmail(): Boolean {
	if (binding.email.text.toString().trim().isEmpty()) {
	binding.emailTextInputLayout.error = "Required Field!"
	binding.email.requestFocus()
	return false
	} else if (!isValidEmail(binding.email.text.toString())) {
	binding.emailTextInputLayout.error = "Invalid Email!"
	binding.email.requestFocus()
	return false
	} else {
	binding.emailTextInputLayout.isErrorEnabled = false
	}
	return true
	}
	/**
	* 1) field must not be empty
	* 2) password lenght must not be less than 6
	* 3) password must contain at least one digit
	* 4) password must contain atleast one upper and one lower case letter
	* 5) password must contain atleast one special character.
	*/
	private fun validatePassword(): Boolean {
	if (binding.password.text.toString().trim().isEmpty()) {
	binding.passwordTextInputLayout.error = "Required Field!"
	binding.password.requestFocus()
	return false
	} else if (binding.password.text.toString().length < 6) {
	binding.passwordTextInputLayout.error = "password can't be less than 6"
	binding.password.requestFocus()
	return false
	} else if (!isStringContainNumber(binding.password.text.toString())) {
	binding.passwordTextInputLayout.error = "Required at least 1 digit"
	binding.password.requestFocus()
	return false
	} else if (!isStringLowerAndUpperCase(binding.password.text.toString())) {
	binding.passwordTextInputLayout.error =
	"Password must contain upper and lower case letters"
	binding.password.requestFocus()
	return false
	} else if (!isStringContainSpecialCharacter(binding.password.text.toString())) {
	binding.passwordTextInputLayout.error = "1 special character required"
	binding.password.requestFocus()
	return false
	} else {
	binding.passwordTextInputLayout.isErrorEnabled = false
	}
	return true
	}
	/**
	* 1) field must not be empty
	* 2) password and confirm password should be same
	*/
	private fun validateConfirmPassword(): Boolean {
	when {
	binding.confirmPassword.text.toString().trim().isEmpty() -> {
	binding.confirmPasswordTextInputLayout.error = "Required Field!"
	binding.confirmPassword.requestFocus()
	return false
	}
	binding.confirmPassword.text.toString() != binding.password.text.toString() -> {
	binding.confirmPasswordTextInputLayout.error = "Passwords don't match"
	binding.confirmPassword.requestFocus()
	return false
	}
	else -> {
	binding.confirmPasswordTextInputLayout.isErrorEnabled = false
	}
	}
	return true
	}
	/**
	* applying text watcher on each text field
	*/
	inner class TextFieldValidation(private val view: View) : TextWatcher {
	override fun afterTextChanged(s: Editable?) {}
	override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {}
	override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
	// checking ids of each text field and applying functions accordingly.
	when (view.id) {
	R.id.userName -> {
	validateUserName()
	}
	R.id.email -> {
	validateEmail()
	}
	R.id.password -> {
	validatePassword()
	}
	R.id.confirmPassword -> {
	validateConfirmPassword()
	}
	}
	}
	}
	}

view raw MainActivity.kt hosted with ❤ by GitHub

You can download the complete source code for this project below:

Download Code

I hope you have learned something new. Stay tuned for more articles like this. Happy coding!