What's New In Kotlin? - Seattle GDG I/O'19 Extended

A look at some of the newest Kotlin features and announcements from 2019 and Google I/O '19.

- New Features
- IO19
- New Learning Opportunities

Specific topics include:
- kotlinx.coroutines
- kotlinx.coroutines.flow
- kotlinx.serialization
- Jetpack Compose
- Kotlin/Everywhere
- etc...

Transcript

1. What’s New In Kotlin? Nate Ebel @n8ebel
2. New Opportunities to Learn Kotlin at #io19 New Features
3. New Opportunities to Learn Kotlin at #io19
4. New Opportunities to Learn
5. • Slides/Links available via Twitter & Speakerdeck • @n8ebel
6. New(ish) Features
7. • Coroutines • Flow • Serialization • And more….
8. Coroutines • “asynchronous, non-blocking code” • kotlinx.coroutines • launch, aysnc • ViewModelScope
9. import kotlinx.coroutines.* fun main() = runBlocking { launch { doWorld() } println("Hello,") } // this is your first suspending function suspend fun doWorld() { delay(1000L) println("World!") } Simple Coroutine
10. class MyViewModel: ViewModel() { init { viewModelScope.launch { // Coroutine that will be canceled // when the ViewModel is cleared. } } } New ViewModelScope
11. Understand Kotlin Coroutines on Android I/O Talk
12. Flow • “asynchronous cold streams” • kotlinx.coroutines.flow • filter, fold, map
13. • Similar to RxJava • Channels = hot • Flow = cold • Multiplatform support
14. val ints: Flow<Int> = flow { for (i in 1..10) { delay(100) emit(i) } } // takes 1 second, prints 10 ints ints.collect { println(it) } Flow In Action https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/index.html
15. kotlinx. serialization • “cross-platform / multi-format reflectionless serialization” • kotlinx.serialization
16. import kotlinx.serialization.* import kotlinx.serialization.json.Json /** * From https://github.com/Kotlin/kotlinx.serialization */ @Serializable data class Data(val a: Int, val b: String = "42") fun main(args: Array<String>) { // serializing objects val jsonData = Json.stringify(Data.serializer(), Data(42)) // serializing lists val jsonList = Json.stringify(Data.serializer().list, listOf(Data(42))) println(jsonData) // {"a": 42, "b": "42"} println(jsonList) // [{"a": 42, "b": "42"}] // parsing data back // b is optional since it has default value val obj = Json.parse(Data.serializer(), """{"a":42}""") println(obj) // Data(a=42, b="42") } Multiplatform Serialization https://github.com/Kotlin/kotlinx.serializationl
17. And more... • Incremental annotation processing for kapt • Unsigned numbers • Cocoapod support for XCode • Kotlin Gradle DSL support for multiplatform projects
18. Kotlin at #io19
19. Kotlin at #io19 Kotlin First
21. Kotlin at #io19 Architecture Components
23. Kotlin at #io19 Jetpack Compose
24. • New, reactive UI toolkit written in Kotlin • Unbundled from framework • Compose UI Library & Compose Compiler
25. @Model class CounterState(var count: Int) @Composable fun Counter() { // introduce a CounterState value. // Instance will be preserved across compositions. // Note: the `+` syntax is temporary val count = +memo { CounterState(0) } // use it to compose your UI. pass it into other composables as parameters Text(text="Count: ${count.count}") // modify the value inside of event handlers, for instance Button(text="Increment, onClick = { count.count += 1; }) } Build Composable UI https://developer.android.com/jetpack/compose
26. class UserListActivity : Activity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContent { AppComponent() } } } Build Composable UI https://developer.android.com/jetpack/compose
27. Kotlin at #io19 Notable Talks
28. • Understand Kotlin Coroutines on Android • Mobile Backends with Kotlin and Google Cloud • What's New in Android • Kotlin Under the Hood: Understand the Internals • Declarative UI Patterns • What’s New In Kotlin On Android, 2 Years In
29. New Learning Opportunities
30. New Learning Opportunities Developing Android Apps with Kotlin by Google
31. • Developing Android Apps with Kotlin by Google • New course from Google & Udacity • Free
32. New Learning Opportunities Kotlin/Everywhere
34. • Kotlin/Everywhere • Community-led events • Learn about Kotlin for Android, Cloud, and Multi-platform development • Apply for support from Google & JetBrains
35. That’s All Folks Thanks!
36. • Kotlin-related talks from Google I/O • Reference for kotlinx.coroutines.flow • Post regarding goals/need for Flow • Discussion around Flow vs Channels vs RxJava • Reference for kotlinx.serialization • Developing Android Apps With Kotlin Course • KOTLIN/Everywhere • ASOP page for Jetpack Compose • Reference for Jetpack Compose @n8ebel