Beyond Java - Kotlin in Android Development

Short introduction to Kotlin programming langugage. Presentation prepared for Poznan Android Developer Group meetup.

Sample project code: https://github.com/mrmike/kotlin-loader-sample

Transcript

1. BEYOND JAVA KOTLIN IN ANDROID DEVELOPMENT @moczul Michał Moczulski
2. Agenda • Introduction • Main goal • Support • Syntax • Sample code • Resources
3. Introduction • Created by JetBrains (July 2011) • Statically typed • Runs on JVM • Fully interoperable with Java • Can be compiled to JavaScript too
4. Main Goal Code contains enough information for the reader but not more.
5. Support • IntelliJ • Eclipse • Maven • Ant • Gradle
6. Production • prezi.com • Telegram • Plastoria • gmc.net
7. Syntax package foo.bar fun main(args: Array<String>) { val foo = (1..100 step 3).filter { it % 2 == 0 } foo.indices.forEach { println("Value at position ${it} is ${foo.get(it)}") } }
8. Object Oriented package foo.bar class Foo(val name: String) { fun sayHello() { println("Hello ${name}") } } fun main(args: Array<String>) { val instance = Foo("Kotlin") instance.sayHello() }
9. When expression when (x) { 0 -> println("The answer is 0") 42 -> println("The answer is 42") else -> println("Else block") }
10. @break fun main(args: Array<String>) { @outer for (i in 1..100) { for (j in 100..1) { if (i < j) { break@outer } } } }
11. Traits package foo.bar trait HelloTrait { val name: String fun sayHello() { println("Hello ${name}") } fun sayBye() { println("Bye") } } class Foo(override val name: String) : HelloTrait { // class methods } fun main(args: Array<String>) { val instance = Foo("Kotlin") instance.sayHello() instance.sayBye() }
12. Data class - old way public class Person { public String name; public String surname; public int age; public Person(String name, String surname, int age) { this.name = name; this.surname = surname; this.age = age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getSurname() { return surname; } public void setSurname(String surname) { this.surname = surname; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } }
13. Data class - Kotlin way data class Person(var name: String, var surname: String, var age: Int)
14. Null safety var name : String = "Foo" name = null // Null can not be a value of a non- null type kotlin.String var numbers : Array<Int>? = array(1, 2, 3, 4, 5) numbers = null // That's ok numbers.size // (1) numbers?.size // (2) numbers!!.size // (3)
15. Sample code https://github.com/mrmike/kotlin-loader-sample
16. Resources • http://kotlinlang.org/ • http://kotlinlang.org/docs/reference/ • http://kotlin-demo.jetbrains.com/ • http://blog.jetbrains.com/kotlin/ • https://github.com/jetbrains/kotlin • http://blog.jetbrains.com/kotlin/2013/08/working-with-kotlin- in-android-studio/
17. Questions?
18. Thank you! Michał Moczulski moczul@gmail.com @moczul https://github.com/mrmike