fun main(args: Array<String>) {
    println("Hello, World!")
// Add CameraX dependencies in your build.gradle file
// implementation "androidx.camera:camera-core:1.1.0"
// implementation "androidx.camera:camera-camera2:1.1.0"

// In your MainActivity.kt

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.camera.core.*
import androidx.camera.lifecycle.ProcessCameraProvider
import androidx.core.content.ContextCompat
import kotlinx.android.synthetic.main.activity_main.*
import java.io.File
import java.util.concurrent.ExecutorService
import java.util.concurrent.Executors

class MainActivity : AppCompatActivity() {

    private var imageCapture: ImageCapture? = null
    private lateinit var cameraExecutor: ExecutorService

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        cameraExecutor = Executors.newSingleThreadExecutor()

        startCamera()

        captureButton.setOnClickListener { takePhoto() }
    }

    private fun startCamera() {
        val cameraProviderFuture = ProcessCameraProvider.getInstance(this)

        cameraProviderFuture.addListener({
            val cameraProvider: ProcessCameraProvider = cameraProviderFuture.get()

            val preview = Preview.Builder()
                .build()
                .also {
                    it.setSurfaceProvider(viewFinder.createSurfaceProvider())
                }

            imageCapture = ImageCapture.Builder()
                .build()

            val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA

            try {
                cameraProvider.unbindAll()

                cameraProvider.bindToLifecycle(
                    this, cameraSelector, preview, imageCapture
                )

            } catch (exc: Exception) {
                // Handle exceptions
            }
        }, ContextCompat.getMainExecutor(this))
    }

    private fun takePhoto() {
        val imageCapture = imageCapture ?: return

        val photoFile = File(externalMediaDirs.firstOrNull(), "${System.currentTimeMillis()}.jpg")

        val outputOptions = ImageCapture.OutputFileOptions.Builder(photoFile).build()

        imageCapture.takePicture(
            outputOptions, cameraExecutor, object : ImageCapture.OnImageSavedCallback {
                override fun onImageSaved(output: ImageCapture.OutputFileResults) {
                    // Handle image saved
                }

                override fun onError(exc: ImageCaptureException) {
                    // Handle error
                }
            }
        )
    }

    override fun onDestroy() {
        super.onDestroy()
        cameraExecutor.shutdown()
    }
}

Kotlin online compiler

Write, Run & Share Kotlin code online using OneCompiler’s Kotlin online compiler for free. It’s a modern and fast online playground for Kotlin, supporting the latest version and ideal for learning, experimenting, and sharing code instantly.

About Kotlin

Kotlin is a statically typed, modern programming language developed by JetBrains. It runs on the JVM and is fully interoperable with Java. Kotlin is concise, expressive, and safe, and it’s officially supported by Google for Android app development.

Sample Code

The following is a simple Kotlin program that prints a greeting:

fun main() {
    println("Hello, OneCompiler!")
}

Taking inputs (stdin)

OneCompiler’s Kotlin editor supports stdin. You can provide input using the I/O tab. Here's a sample program that reads a line of input and prints a greeting:

fun main() {
    print("Enter your name: ")
    val name = readLine()
    println("Hello, $name")
}

Syntax Basics

Variables

val name: String = "OneCompiler"  // Immutable
var age: Int = 25                 // Mutable

Kotlin supports type inference, so explicit types are optional:

val city = "Hyderabad"
var count = 10

Conditionals

val score = 85
if (score >= 50) {
    println("Pass")
} else {
    println("Fail")
}

Loops

For loop

for (i in 1..5) {
    println(i)
}

While loop

var i = 1
while (i <= 5) {
    println(i)
    i++
}

Do-While loop

var j = 1
do {
    println(j)
    j++
} while (j <= 5)

Functions

fun add(a: Int, b: Int): Int {
    return a + b
}

fun greet(name: String) = "Hello, $name"

Collections

val items = listOf("apple", "banana", "cherry")
for (item in items) {
    println(item)
}

This guide provides a quick reference to Kotlin programming syntax and features. Start coding in Kotlin using OneCompiler’s Kotlin online compiler today!