How to Use Kotlin in Android Studio: A Beginner's Guide

To use Kotlin in Android Studio, create a new project and select Kotlin as the programming language. Write your Kotlin code in .kt files inside the src/main/java folder, then build and run your app using the built-in emulator or a device.

Syntax

Kotlin code is written in .kt files. A basic Kotlin program has a fun main() function as the entry point. Use val for constants and var for variables. Functions are declared with fun keyword.

kotlin

fun main() {
    val greeting: String = "Hello, Android Studio!"
    println(greeting)
}

Output

Hello, Android Studio!

Example

This example shows a simple Android app using Kotlin that displays a greeting message on the screen.

kotlin

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import android.widget.TextView

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val textView = TextView(this)
        textView.text = "Hello, Kotlin in Android Studio!"
        setContentView(textView)
    }
}

Output

The app screen shows the text: Hello, Kotlin in Android Studio!

Common Pitfalls

Beginners often forget to select Kotlin when creating a new project, causing errors. Another common mistake is mixing Java and Kotlin syntax incorrectly. Also, forgetting to call setContentView() in an activity will result in a blank screen.

kotlin

/* Wrong: Missing setContentView */
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val textView = TextView(this)
        textView.text = "Hello"
        // setContentView(textView) is missing
    }
}

/* Right: Include setContentView */
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val textView = TextView(this)
        textView.text = "Hello"
        setContentView(textView)
    }
}

Quick Reference

• Create a new project in Android Studio and choose Kotlin as the language.
• Write Kotlin code in .kt files inside src/main/java.
• Use fun to declare functions and val/var for variables.
• Run your app on an emulator or device using the Run button.

Key Takeaways

Always select Kotlin as the language when creating a new Android Studio project.

Write Kotlin code inside .kt files under the src/main/java directory.

Use fun to define functions and remember to call setContentView() in activities.

Run your app using the built-in emulator or a connected Android device.

Avoid mixing Java and Kotlin syntax without proper understanding.