Introduction

Welcome to this beginner-friendly tutorial on building your first Android app using Kotlin. The goal of this tutorial is to guide you through the process of creating a simple Android app from scratch. By the end of this tutorial, you'll have a basic understanding of Android app development with Kotlin and will have your own app displaying a message on the screen.

What you will learn:

• How to create an Android project in Android Studio
• Writing basic Kotlin code
• Displaying a message on the screen

Prerequisites:

• Basic understanding of programming concepts
• Android Studio installed on your computer

Step-by-Step Guide

1. Creating a New Android Project

First, you need to create a new Android project. Open Android Studio, choose "New Project", select "Empty Activity", and click "Next". Name your project, choose "Kotlin" as the language, and select the minimum SDK you want your app to support.

1. Understanding the Main Files

Two main files are automatically created: MainActivity.kt and activity_main.xml. The former is where you'll write Kotlin code and the latter is for designing the app layout.

1. Writing Kotlin Code

Open MainActivity.kt. Inside the onCreate method, write the code to display a message. Use the Toast class for this purpose.

Code Examples

1. Creating a toast message in Kotlin:

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

    // Create a toast message
    val toast = Toast.makeText(this, "Hello, World!", Toast.LENGTH_LONG)
    toast.show()
}

Explanation:

• Toast.makeText(this, "Hello, World!", Toast.LENGTH_LONG) creates a new toast message that says "Hello, World!".
• toast.show() displays the toast message on the screen.

Expected outcome: When you launch the app, you should see a "Hello, World!" message pop up at the bottom of the screen.

Summary

In this tutorial, you learned how to create a new Android project in Android Studio, write simple Kotlin code, and display a toast message on the screen. The next steps could be learning how to handle user interaction, navigating between screens, and retrieving data from the internet. For more advanced topics, check out the official Android Developers documentation and Kotlin language guide.

Practice Exercises

1. Create an app that displays a different message.
2. Modify the app to display the toast message when a button is clicked.

Solutions:

1. Just replace "Hello, World!" with your new message in the Toast.makeText() method.
2. You need to create a button in activity_main.xml, give it an id, and then use findViewById<Button>(R.id.button_id).setOnClickListener to set an onClick listener in MainActivity.kt.

Remember to always practice what you've learned to consolidate your knowledge. Happy coding!