EditText Input Validations with Android

Phone number validation

In this example, we have an EditText with an id etPhoneNumber in the XML layout file. The inputType attribute is set to “phone” to allow the user to enter a phone number. This input type helps in displaying a numeric keyboard with additional symbols commonly used in phone numbers.

In the Kotlin code, we add a TextWatcher to the EditText to perform the validation. In the afterTextChanged() method, we retrieve the entered text, trim any leading or trailing spaces, and check if it is a valid phone number using the isValidPhoneNumber() function.

The isValidPhoneNumber() function uses PhoneNumberUtils.isGlobalPhoneNumber() to validate the phone number. It checks if the provided string is a valid global phone number according to the rules of the country or region the user is currently in.

If the entered value is not a valid phone number or is empty, we set an error message using setError() on the EditText to indicate that a valid phone number is required. If the input is a valid phone number, we clear the error.

<EditText
    android:id="@+id/etPhoneNumber"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:hint="Enter a phone number"
    android:inputType="phone"
    android:imeOptions="actionDone"
    />

import android.os.Bundle
import android.telephony.PhoneNumberUtils
import android.text.Editable
import android.text.TextUtils
import android.text.TextWatcher
import android.widget.EditText
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {
    private lateinit var etPhoneNumber: EditText
    
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        etPhoneNumber = findViewById(R.id.etPhoneNumber)
        
        // Perform validation using a TextWatcher
        etPhoneNumber.addTextChangedListener(object : TextWatcher {
            override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
                // Not needed for this example
            }
    
            override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
                // Not needed for this example
            }
    
            override fun afterTextChanged(s: Editable?) {
                val phoneNumber = s.toString().trim()
                if (TextUtils.isEmpty(phoneNumber) || !isValidPhoneNumber(phoneNumber)) {
                    etPhoneNumber.error = "Please enter a valid phone number"
                } else {
                    etPhoneNumber.error = null
                }
            }
        })
    }
    
    private fun isValidPhoneNumber(phoneNumber: String): Boolean {
        return PhoneNumberUtils.isGlobalPhoneNumber(phoneNumber)
    }
}

Note that you could also use a patterns matcher to validate the phone number. The code would look then something like the following.

import android.os.Bundle
import android.text.Editable
import android.text.TextUtils
import android.text.TextWatcher
import android.util.Patterns
import android.widget.EditText
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {
    private lateinit var etPhoneNumber: EditText
    
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        
        etPhoneNumber = findViewById(R.id.etPhoneNumber)
        
        // Perform validation using a TextWatcher
        etPhoneNumber.addTextChangedListener(object : TextWatcher {
            override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {
                // Not needed for this example
            }
    
            override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {
                // Not needed for this example
            }
    
            override fun afterTextChanged(s: Editable?) {
                val phoneNumber = s.toString().trim()
                if (TextUtils.isEmpty(phoneNumber) || !isValidPhoneNumber(phoneNumber)) {
                    etPhoneNumber.error = "Please enter a valid phone number"
                } else {
                    etPhoneNumber.error = null
                }
            }
        })
    }
    
    private fun isValidPhoneNumber(phoneNumber: String): Boolean {
        return Patterns.PHONE.matcher(phoneNumber).matches()
    }
}