Update An introduction to Kotlin for Android development

Google announced that it is making Kotlin, a statically typed programming language for the Java Virtual Machine, a first-class language for writing Android apps. Kotlin’s primary sponsor is JetBrains, the company behind tools like IntelliJ.

It’s 100 percent interoperable with Java, which until now was Google’s primary language for writing Android apps (besides C++).

Key Summary

• Overview: The article introduces Kotlin, a modern programming language officially supported by Google for Android development, emphasizing its advantages over Java.
• Key Features:
  • Concise Syntax: Reduces boilerplate code, making development faster and code easier to read (e.g., data classes, null safety).
  • Null Safety: Built-in null pointer exception prevention, improving app stability.
  • Interoperability: Fully compatible with Java, allowing gradual adoption in existing projects.
  • Coroutines: Simplifies asynchronous programming (e.g., API calls, database operations) with lightweight, non-blocking code.
  • Type Safety: Strong typing and smart casts reduce runtime errors.
• Use Cases: Ideal for building Android apps, from simple utilities to complex, high-performance applications, especially with Android Jetpack integration.
• Benefits:
  • Increases developer productivity with concise, expressive code.
  • Enhances app reliability by reducing common errors like null pointer exceptions.
  • Backed by Google, ensuring long-term support and community growth.
• Challenges: Learning curve for developers new to Kotlin’s advanced features; slightly slower compilation times compared to Java in some cases.
• Conclusion: Kotlin is a powerful, developer-friendly language for Android development, offering modern features, improved safety, and seamless Java integration, making it a preferred choice for building robust apps.

What is Kotlin ?

Kotlin is a great fit for developing Android applications, bringing all of the advantages of a modern language to the Android platform without introducing any new restrictions:

Compatibility: Kotlin is fully compatible with JDK 6, ensuring that Kotlin applications can run on older Android devices with no issues. The Kotlin tooling is fully supported in Android Studio and compatible with the Android build system.

Performance: A Kotlin application runs as fast as an equivalent Java one, thanks to very similar bytecode structure. With Kotlin’s support for inline functions, code using lambdas often runs even faster than the same code written in Java.

Interoperability: Kotlin is 100% interoperable with Java, allowing to use all existing Android libraries in a Kotlin application. This includes annotation processing, so data binding and Dagger work too.

Footprint – Kotlin has a very compact runtime library, which can be further reduced through the use of

ProGuard – In a real application, the Kotlin runtime adds only a few hundred methods and less than 100K to the size of the .apk file.

Compilation Time: Kotlin supports efficient incremental compilation, so while there’s some additional overhead for clean builds, incremental builds are usually as fast or faster than with Java.

Learning Curve: For a Java developer, getting started with Kotlin is very easy. The automated Java to Kotlin converter included in the Kotlin plugin helps with the first steps. Kotlin Koans offer a guide through the key features of the language with a series of interactive exercises.

Use Android APIs with Kotlin

Kotlin provides complete interoperability with the Java language, so calling the Android APIs often looks exactly like the matching Java code. Except now you can combine those method calls with Kotlin’s syntax features.

Here are a few examples of what it looks like to call Android APIs in Kotlin, compared to the same code in Java language:

Syntax differences with KOTLIN and JAVA.

• Declare Activity in Kotlin

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

public class MainActivity extends AppCompatActivity {
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
  }
}

• On-click listener in Kotlin

val fab = findViewById(R.id.fab) as FloatingActionButton
fab.setOnClickListener {
  ...
}

• On-click listener in Java

FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
  @Override
  public void onClick(View view) {
    ...
  }
});

Kotlin is like Swift.

BASIC

Hello Android Programme

print("Hello, Android!")

println("Hello, Android!")

Variables And Constants

var age = 42
age = 50
let mConstant = 42

var age = 42
age = 50
val mConstant = 42

COLLECTIONS

Arrays

var deviceList = ["Android", "iOS", "Window"]
	deviceList[1] = "iOS"

val deviceList = arrayOf("Android", "iOS", "Window")
deviceList[1] = "iOS"

Maps

var job = [
  	 	 "KP": "CEO",
   		 "MS": "Sr. Android Developer",
	]
	job["HM"] = "Public Relations"

val job = mutableMapOf(
    		"KP" to "CEO",
  		  "MS" to "Sr. Android Developer"
	)
	job["Jayne"] = "Public Relations"

REFERENCES :

https://kotlinlang.org/docs/reference/android-overview.html
http://nilhcem.com/swift-is-like-kotlin/
https://developer.android.com/kotlin/get-started.html#use-android-apis-with-kotlin