Phone Number Validation in Android using Jetpack Compose

Phone numbers are used in many android applications to validate the user with the phone number. In this application, we will look at how to validate the phone number in an android application using Jetpack Compose. A sample video is given below to get an idea about what we are going to do in this article.

Step by Step Implementation

Step 1: Create a New Project in Android Studio

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. While choosing the template, select Empty Compose Activity. If you do not find this template, try upgrading the Android Studio to the latest version. We demonstrated the application in Kotlin, so make sure you select Kotlin as the primary language while creating a New Project.

Step 2: Adding a new color to the Color.kt file

Navigate to app > java > your app’s package name > ui.theme > Color.kt file and add the below code to it. 

Kotlin

package com.example.testproject.ui.theme

import androidx.compose.ui.graphics.Color

val Purple200 = Color(0xFF0F9D58)
val Purple500 = Color(0xFF0F9D58)
val Purple700 = Color(0xFF3700B3)
val Teal200 = Color(0xFF03DAC5)

// on below line we are adding different colors.
val greenColor = Color(0xFF0F9D58)

Step 3: Working with the MainActivity.kt file

Go to the MainActivity.kt file and refer to the following code. Below is the code for the MainActivity.kt file. Comments are added inside the code to understand the code in more detail.

Kotlin

package com.example.testproject

import android.annotation.SuppressLint
import android.os.Bundle
import android.util.Log
import android.widget.Toast
import androidx.activity.ComponentActivity
import androidx.activity.compose.setContent
import androidx.compose.foundation.layout.*
import androidx.compose.material.*
import androidx.compose.runtime.Composable
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.platform.LocalContext
import androidx.compose.ui.text.TextStyle
import androidx.compose.ui.text.font.FontFamily
import androidx.compose.ui.text.font.FontWeight
import androidx.compose.ui.text.input.TextFieldValue
import androidx.compose.ui.text.style.TextAlign
import androidx.compose.ui.tooling.preview.Preview
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.sp
import androidx.core.content.ContextCompat.startActivity
import com.example.testproject.ui.theme.TestProjectTheme
import com.example.testproject.ui.theme.greenColor

class MainActivity : ComponentActivity() {
    @SuppressLint("UnusedMaterialScaffoldPaddingParameter")
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            TestProjectTheme {
                // on below line we are specifying
                // background color for our application
                Surface(
                    modifier = Modifier.fillMaxSize(),
                    color = MaterialTheme.colors.background
                ) {
                    // on below line we are specifying theme as scaffold.
                    Scaffold(
                        // in scaffold we are specifying top bar.
                        topBar = {
                            // inside top bar we are specifying
                              // background color
                            TopAppBar(backgroundColor = greenColor,
                                // along with that we are specifying
                                // title for our top bar.
                                title = {
                                    // in the top bar we are specifying
                                      // tile as a text
                                    Text(
                                        // on below line we are specifying
                                        // text to display in top app bar.
                                        text = "GFG",

                                        color = Color.White,

                                        // on below line we are specifying
                                        // modifier to fill max width.
                                        modifier = Modifier.fillMaxWidth(),

                                        // on below line we are
                                        // specifying text alignment.
                                        textAlign = TextAlign.Center,

                                        // on below line we are
                                        // specifying color for our text.
                                    )
                                }
                            )
                        }
                    ) {
                        // on below line we are calling validate
                        // phone method to check phone number.
                        validatePhone()
                    }
                }
            }
        }
    }
}

@Composable
fun validatePhone() {

    // in the below line, we are
    // creating variables for URL
    val phoneNumber = remember {
        mutableStateOf(TextFieldValue())
    }

    // on below line we are creating
    // a variable for a context
    val ctx = LocalContext.current

    // on below line we are creating a column
    Column(
        // on the below line we are specifying modifier
        // and setting max height and max width
        // for our column
        modifier = Modifier
            .fillMaxSize()
            .fillMaxHeight()
            .fillMaxWidth()
            // on below line we are
            // adding padding for our column
            .padding(5.dp),
        // on below line we are specifying horizontal
        // and vertical alignment for our column
        horizontalAlignment = Alignment.CenterHorizontally,
        verticalArrangement = Arrangement.Center
    ) {

        // in the below line, we are creating a text field
        // for getting URL from user.
        TextField(
            // on below line we are specifying value
            // for our  text field.
            value = phoneNumber.value,

            // on below line we are adding on
            // value change for text field.
            onValueChange = { phoneNumber.value = it },

            // on below line we are adding place holder as text
            placeholder = { Text(text = "Enter your phone number") },

            // on below line we are adding modifier to it
            // and adding padding to it and filling max width
            modifier = Modifier
                .padding(16.dp)
                .fillMaxWidth(),

            // on below line we are adding text style
            // specifying color and font size to it.
            textStyle = TextStyle(color = Color.Black, fontSize = 15.sp),

            // on below line we are
            // adding single line to it.
            singleLine = true,
        )

        // on below line adding a spacer.
        Spacer(modifier = Modifier.height(20.dp))

        // on below line adding a button to open URL
        Button(onClick = {
            // on below line we are validating our phone number.
            if (phoneNumber.value.text.isNotEmpty()) {
                if (android.util.Patterns.PHONE.matcher(phoneNumber.value.text).matches()) {
                    Toast.makeText(ctx, "Phone Number is valid..", Toast.LENGTH_SHORT).show()
                } else {
                    Toast.makeText(ctx, "Phone Number is invalid..", Toast.LENGTH_SHORT).show()
                }
            } else {
                Toast.makeText(ctx, "Please enter phone number", Toast.LENGTH_SHORT).show()
            }

        }) {
            // on the below line creating a text for our button.
            Text(
                // on below line adding a text ,
                // padding, color and font size.
                text = "Validate Phone Number",
                modifier = Modifier.padding(10.dp),
                color = Color.White,
                fontSize = 15.sp
            )
        }
    }
}

Now run your application to see the output of it. 

Output: