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
   

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2. Kotlin
   

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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
   

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4. Pragmatic
   Ergonomic
   Constant feedback loop
   

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5. Kotlin
   ● Object Oriented and Functional
   ● Static typing with type inference
   ● Safe
   ● Concise
   

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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
   

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7. package hello
   fun main() {
   println("Hello World")
   }
   Kotlin
   ● Object Oriented and Functional
   ● Static typing with type inference
   ● Safe
   ● Concise
   

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8. History
   Kotlin is announced
   Creation of Kotlin by
   Jetbrains
   2011 2012 2013 2014 2015 2016 2017 2018 2019 ?
   

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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
   

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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
    

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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
    

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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
    

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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
    

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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
    ?
    

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15. Android SDK
    Java application development
    2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020
    Android Development
    

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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
    

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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
    

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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
    

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19. Kotlin First
    

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20. Kotlin First
    

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21. Personal Kotlin’s
    Favorites
    

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22. Null Safety
    Aims to eliminate NullPointerException
    

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23. var a: String = "abc"
    a = null
    Null Safety
    Aims to eliminate NullPointerException
    

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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
    

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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)
    

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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
    

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27. Asynchronous Operations
    Coroutines are light-weight threads
    

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28. import kotlinx.coroutines.*
    fun main() {
    GlobalScope.launch {
    delay(1000L)
    println("World!")
    }
    print("Hello, ")
    Thread.sleep(2000L)
    }
    Asynchronous Operations
    Coroutines are light-weight threads
    

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29. import kotlinx.coroutines.*
    fun main() {
    GlobalScope.launch {
    delay(1000L)
    println("World!")
    }
    print("Hello, ")
    Thread.sleep(2000L)
    }
    Asynchronous Operations
    Coroutines are light-weight threads
    

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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,
    

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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!
    

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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!
    

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33. Extension Functions
    Add functionality to a type,
    without directly modifying the type’s definition
    

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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
    

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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
    

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36. Developer
    Experience
    

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37. Android Studio Kotlin
    ● Kotlin plugin is part of Android Studio
    ● Lint checks & refactoring support
    ● Project templates and samples
    ● Kotlin-friendly Android SDK (nullability)
    

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38. Android Studio Kotlin
    ● Kotlin plugin is part of Android Studio
    ● Lint checks & refactoring support
    ● Project templates and samples
    ● Kotlin-friendly Android SDK (nullability)
    

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39. Kapt is incremental now
    

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40. Android Studio Kotlin
    

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41. R8 Kotlin
    

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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")
    }
    }
    

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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");
    }
    }
    }
    

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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
    

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45. Kotlin’s Adoption
    

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46. Kotlin’s Adoption
    

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47. Google Apps Kotlin
    

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48. Android Kotlin
    

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49. Android Jetpack Kotlin & Coroutines
    ● Kotlin-friendly APIs
    ● Room suspend functions
    ● WorkManager CoroutineWorker
    ● Lifecycles & ViewModel coroutine scopes
    ● + more KTX libraries...
    

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50. Android KTX (core)
    sharedPreferences
    .edit() // create an Editor
    .putBoolean("key", value)
    .apply() // write to disk asynchronously
    Default APIs
    

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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
    

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52. youtu.be/BOHK_w09pVA
    

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53. Jetpack Compose
    ● Reactive UI toolkit
    ● Unbundled from Android Framework
    ● Developer Preview
    ● Android Studio v4.0
    

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54. @Composable
    fun Greeting(name: String) {
    Text("Hello $name")
    }
    Jetpack Compose
    ● Reactive UI toolkit
    ● Unbundled from Android Framework
    ● Developer Preview
    ● Android Studio v4.0
    

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55. Jetpack Compose
    ● Reactive UI toolkit
    ● Unbundled from Android Framework
    ● Developer Preview
    ● Android Studio v4.0
    github.com/android/compose-samples/tree/master/JetNews
    

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56. youtu.be/dtm2h-_sNDQ
    

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57. Documentation Kotlin
    ● Migration to Kotlin pages
    ● Code snippets in Kotlin
    ● Switch between Java and Kotlin
    

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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
    

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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
    

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60. Community
    
    Kotlin
    

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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()
    }
    

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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
    

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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
    

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64. Kotlin multiplatform
    

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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
    

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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
    

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67. Is Kotlin mobile only
    

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68. ● Framework Web
    ● Client/Server
    ● 100% Kotlin
    ● Multi-platform
    fun main(args: Array) {
    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)
    }
    

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69. Spring boot and Kotlin
    spring.io/guides/tutorials/spring-boot-kotlin/
    

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70. KOTLIN ON GOOGLE CLOUD PLATFORM
    A community-supported project
    codelabs.developers.google.com/codelabs/cloud-kotlin-emojify/
    

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71. Kotlin
    future?
    

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72. ●
    More Coroutines!
    ●
    More Multi-Platform
    ●
    Even better developer experience
    

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73. Thanks
    Pietro Maggi
    @pfmaggi
    

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