Kotlin in 2019

For most developers who used Kotlin, their experience started on mobile with Android when the official support was announced in 2017. Since then, the language has evolved and its support has continuously improved. In this presentation, I will talk about the current state of Kotlin on Android but also on other platforms and a preview of its future.

Transcript

1. Kotlin in 2019 Pietro Maggi @pfmaggi
2. Kotlin
3. Language design is cast in stone, but this stone is reasonably soft, and with some effort we can reshape it later. Kotlin Design Team
4. Pragmatic Ergonomic Constant feedback loop
5. Kotlin • Object Oriented and Functional • Static typing with type inference • Safe • Concise
6. package hello; class HelloWorld { public static void main(String args[]) { System.out.println("Hello, World"); } } Kotlin • Object Oriented and Functional • Static typing with type inference • Safe • Concise
7. package hello fun main() { println("Hello World") } Kotlin • Object Oriented and Functional • Static typing with type inference • Safe • Concise
8. History Kotlin is announced Creation of Kotlin by Jetbrains 2011 2012 2013 2014 2015 2016 2017 2018 2019 ?
9. History Kotlin is announced Creation of Kotlin by Jetbrains 2011 2012 2013 2014 2015 2016 2017 2018 2019 ? Kotlin is released Development tools are open source
10. History Kotlin is announced Creation of Kotlin by Jetbrains 2011 2012 2013 2014 2015 2016 2017 2018 2019 ? Kotlin is released Development tools are open source Kotlin 1.0 First stable
11. History Kotlin is announced Creation of Kotlin by Jetbrains Kotlin 1.1 (March) JavaScript support Coroutines introduction 2011 2012 2013 2014 2015 2016 2017 2018 2019 ? Kotlin is released Development tools are open source Kotlin 1.0 First stable
12. History Kotlin is announced Creation of Kotlin by Jetbrains Kotlin 1.1 (March) JavaScript support Coroutines introduction 2011 2012 2013 2014 2015 2016 2017 2018 2019 ? Kotlin is released Development tools are open source Kotlin 1.0 First stable Kotlin 1.2 (November) Code sharing between platforms
13. History Kotlin is announced Creation of Kotlin by Jetbrains Kotlin 1.3 (October) Coroutines stable (JVM) Kotlin/Native beta Kotlin 1.1 (March) JavaScript support Coroutines introduction 2011 2012 2013 2014 2015 2016 2017 2018 2019 ? Kotlin is released Development tools are open source Kotlin 1.0 First stable Kotlin 1.2 (November) Code sharing between platforms
14. History Kotlin is announced Creation of Kotlin by Jetbrains Kotlin 1.3 (October) Coroutines stable (JVM) Kotlin/Native beta Kotlin 1.1 (March) JavaScript support Coroutines introduction 2011 2012 2013 2014 2015 2016 2017 2018 2019 ? Kotlin is released Development tools are open source Kotlin 1.0 First stable Kotlin 1.2 (November) Code sharing between platforms Kotlin 1.4 ?
15. Android SDK Java application development 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Android Development
16. Android SDK Java application development 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Android NDK C and C ++ support for games and cross-platform library/applications Android Development
17. Android SDK Java application development 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Kotlin on Android Official support Android NDK C and C ++ support for games and cross-platform library/applications Android Development
18. Android SDK Java application development 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 Kotlin on Android Official support Android NDK C and C ++ support for games and cross-platform library/applications Android Development Kotlin First Kotlin-First APIs
19. Kotlin First
20. Kotlin First
21. Personal Kotlin’s Favorites
22. Null Safety Aims to eliminate NullPointerException
23. var a: String = "abc" a = null Null Safety Aims to eliminate NullPointerException
24. var a: String = "abc" a = null Null Safety Aims to eliminate NullPointerException > Null can not be a value of a non-null type String
25. var a: String = "abc" a = null Null Safety Aims to eliminate NullPointerException > Null can not be a value of a non-null type String var b: String? = "abc" b = null print(b)
26. var a: String = "abc" a = null Null Safety Aims to eliminate NullPointerException > Null can not be a value of a non-null type String var b: String? = "abc" b = null print(b) > null
27. Asynchronous Operations Coroutines are light-weight threads
28. import kotlinx.coroutines.* fun main() { GlobalScope.launch { delay(1000L) println("World!") } print("Hello, ") Thread.sleep(2000L) } Asynchronous Operations Coroutines are light-weight threads
29. import kotlinx.coroutines.* fun main() { GlobalScope.launch { delay(1000L) println("World!") } print("Hello, ") Thread.sleep(2000L) } Asynchronous Operations Coroutines are light-weight threads
30. import kotlinx.coroutines.* fun main() { GlobalScope.launch { delay(1000L) println("World!") } print("Hello, ") Thread.sleep(2000L) } Asynchronous Operations Coroutines are light-weight threads > Hello,
31. import kotlinx.coroutines.* fun main() { GlobalScope.launch { delay(1000L) println("World!") } print("Hello, ") Thread.sleep(2000L) } Asynchronous Operations Coroutines are light-weight threads > Hello, World!
32. import kotlinx.coroutines.* fun main() { GlobalScope.launch { delay(1000L) println("World!") } print("Hello, ") Thread.sleep(2000L) } Asynchronous Operations Coroutines are light-weight threads > Hello, World!
33. Extension Functions Add functionality to a type, without directly modifying the type’s definition
34. fun Byte.toUnsigned(): Int { return if (this < 0) this + 256 else this.toInt() } Extension Functions Add functionality to a type, without directly modifying the type’s definition
35. fun Byte.toUnsigned(): Int { return if (this < 0) this + 256 else this.toInt() } Extension Functions Add functionality to a type, without directly modifying the type’s definition val x: Byte = -1 println(x.toUnsigned()) > 255
36. Developer Experience
37. Android Studio Kotlin • Kotlin plugin is part of Android Studio • Lint checks & refactoring support • Project templates and samples • Kotlin-friendly Android SDK (nullability)
38. Android Studio Kotlin • Kotlin plugin is part of Android Studio • Lint checks & refactoring support • Project templates and samples • Kotlin-friendly Android SDK (nullability)
39. Kapt is incremental now
40. Android Studio Kotlin
41. R8 Kotlin
42. Kotlin’s Companion Object fun main() { println(Greeter.hello().greet("Olive")) } class Greeter(val greeting: String) { fun greet(name: String) = "$greeting, $name!" companion object { fun hello() = Greeter("Hello") } }
43. Companion Object… as seen from Java public final class Greeter { public static final Companion Companion = new Companion(); private final String greeting; public Greeter(String greeting) { this.greeting = greeting; } public String getGreeting() { return greeting; } public String greet(String name) { return greeting + ", " + name; } public static final class Companion { private Companion() {} public Greeter hello() { return new Greeter("Hello"); } } }
44. public final class Greeter { - public static final Companion Companion = new Companion(); private final String greeting; - public static final class Companion { - private Companion() {} - - public Greeter hello() { - return new Greeter("Hello"); - } - } + public static Greeter hello() { + return new Greeter("Hello"); + } public String greet(String name) { return greeting + ", " + name; } } Fortunately there’s R8
45. Kotlin’s Adoption
46. Kotlin’s Adoption
47. Google Apps Kotlin
48. Android Kotlin
49. Android Jetpack Kotlin & Coroutines • Kotlin-friendly APIs • Room suspend functions • WorkManager CoroutineWorker • Lifecycles & ViewModel coroutine scopes • + more KTX libraries...
50. Android KTX (core) sharedPreferences .edit() // create an Editor .putBoolean("key", value) .apply() // write to disk asynchronously Default APIs
51. Android KTX (core) sharedPreferences .edit() // create an Editor .putBoolean("key", value) .apply() // write to disk asynchronously sharedPreferences.edit { putBoolean("key", value) } Default APIs with core-ktx, syntactic sugar on top of the same APIs
52. youtu.be/BOHK_w09pVA
53. Jetpack Compose • Reactive UI toolkit • Unbundled from Android Framework • Developer Preview • Android Studio v4.0
54. @Composable fun Greeting(name: String) { Text("Hello $name") } Jetpack Compose • Reactive UI toolkit • Unbundled from Android Framework • Developer Preview • Android Studio v4.0
55. Jetpack Compose • Reactive UI toolkit • Unbundled from Android Framework • Developer Preview • Android Studio v4.0 github.com/android/compose-samples/tree/master/JetNews
56. youtu.be/dtm2h-_sNDQ
57. Documentation Kotlin • Migration to Kotlin pages • Code snippets in Kotlin • Switch between Java and Kotlin
58. • Kotlin Koans: kotlinlang.org/docs/tutorials/koans.html • Kotlin Playground play.kotlinlang.org • Udacity ◦ Kotlin Bootcamp for Programmers ◦ Developing Android Apps with Kotlin ◦ Advanced Android with Kotlin Learning Kotlin
59. • Google I/O and ADS apps: github.com/google/iosched • Sunflower: github.com/android/sunflower • Plaid: github.com/android/plaid • More Samples: developer.android.com/samples?language=kotlin Samples Kotlin
60. Community Kotlin
61. OkHttp • Client HTTP • Created by Square • 100% Kotlin since version 4 fun post(url: String, json: String): String { val mediaType = MediaType.parse("application/json;charset=utf-8") val client = OkHttpClient() val body = RequestBody.create(mediaType, json) val request = Request.Builder().url(url).post(body).build() val response = client.newCall(request).execute() return response.body().string() }
62. SQLDelight • Generates typesafe Kotlin APIs from SQL • Created by Square • 100% Kotlin • Multi-platform (supported SQLite drivers on Android, JVM and iOS) selectAll: SELECT * FROM hockeyPlayer; insert: INSERT INTO hockeyPlayer(player_number, full_name) VALUES (?, ?); insertFullPlayerObject: INSERT INTO hockeyPlayer(player_number, full_name) VALUES ?; Player.sq
63. SQLDelight • Generates typesafe Kotlin APIs from SQL • Created by Square • 100% Kotlin • Multi-platform (supported SQLite drivers on Android, JVM and iOS) val database = Database(driver) val playerQueries: PlayerQueries = database.playerQueries println(playerQueries.selectAll().executeAsList()) // Prints [HockeyPlayer.Impl(15, "Ryan Getzlaf")] playerQueries.insert(player_number = 10, full_name = "Corey Perry") println(playerQueries.selectAll().executeAsList()) // Prints [HockeyPlayer.Impl(15, "Ryan Getzlaf"), ...] val player = HockeyPlayer(10, "Ronald McDonald") playerQueries.insertFullPlayerObject(player) PlayerQueries.kt
64. Kotlin multiplatform
65. Component Status entered at Mode for Sources Mode for Binaries Kotlin/JVM v1.0 Fully Stable Fully Stable Kotlin/JS v1.1 AIR* Moving Fast Kotlin/Native v1.3 AIR* Moving Fast Kotlin Scripts (*.kts) v1.2 AIR* Moving Fast Multi-Platform Projects v1.2 Moving Fast Moving Fast Coroutines v1.3 Fully Stable Fully Stable Stability of Different Components * Additions in Incremental Releases
66. Libraries • SQLDelight: SQLite model facilitation library • SQLiter: SQLite access driver. Powering the SQLDelight native driver • Multiplatform Settings: Save simple key-value data • Kotlinx.Serialization: cross-platform / multi-format reectionless serialization • Kotlinx.Coroutines: Support library for coroutines • Stately: State utility library Kotlin Multiplatform Samples • Kotlinconf App: Kotlinconf schedule app, iOS/Android/Backend • DroidconKotlin: Droidcon NY/SF schedule app, iOS/Android/Web • Sudoku: iOS/Android sample game
67. Is Kotlin mobile only
68. • Framework Web • Client/Server • 100% Kotlin • Multi-platform fun main(args: Array<String>) { val server = embeddedServer(Netty, port = 8080) { routing { get("/") { call.respondText( "Hello World!", ContentType.Text.Plain ) } get("/demo") { call.respondText("HELLO WORLD!") } } } server.start(wait = true) }
69. Spring boot and Kotlin spring.io/guides/tutorials/spring-boot-kotlin/
70. KOTLIN ON GOOGLE CLOUD PLATFORM A community-supported project codelabs.developers.google.com/codelabs/cloud-kotlin-emojify/
71. Kotlin future?
72. • More Coroutines! • More Multi-Platform • Even better developer experience
73. Thanks Pietro Maggi @pfmaggi