Kotlin First - Taking Advantage of Kotlin for Android Development // 360AnDev 2020

What does it mean to be "Kotlin First"?

How can you start taking full advantage of Kotlin for Android development?

Transcript

1. Kotlin First Taking Full Advantage of Kotlin for Android Development ANDROID DEVELOPER @n8ebel www.goobar.io Nate Ebel
2. Kotlin First
3. How can we take full advantage of Kotlin?
4. Taking Full Advantage of Kotlin Migrating Java Syntax & Features Kotlin Standard Library Coroutines & Flow Jetpack Compose Kotlin Multiplatform
5. Taking Full Advantage of Kotlin New To Kotlin Kotlin Practitioner Kotlin Veteran
6. The Kotlin Journey
7. How do I start? Am I doing this right? I’m convinced I love Kotlin
8. Taking Full Advantage of Kotlin Get Started With Kotlin Idiomatic Kotlin Going Full Kotlin Kotlin Beyond Android
9. Taking Full Advantage of Kotlin Idiomatic Kotlin Going Full Kotlin Kotlin Beyond Android New Projects Converting Java Experimentation
10. Taking Full Advantage of Kotlin Going Full Kotlin Kotlin Beyond Android New Projects Converting Java Experimentation Syntax Kotlin Standard Library Language Features
11. Taking Full Advantage of Kotlin Kotlin Beyond Android New Projects Converting Java Experimentation Syntax Kotlin Standard Library Language Features Android Jetpack Coroutines/Flow Buildscripts/Libraries
12. Taking Full Advantage of Kotlin New Projects Converting Java Experimentation Syntax Kotlin Standard Library Language Features Android Jetpack Coroutines/Flow Buildscripts/Libraries Kotlin Multiplatform Server-side Kotlin Kotlin Scripting
13. Taking Advantage of Kotlin for Android Development
14. Getting Started With Kotlin How do I start?
15. Create A New Android Studio Project
17. Convert Existing Java to Kotlin
18. Paste Java Into a Kotlin File
19. Quickly Evaluate Kotlin Code
20. Quickly Evaluate Kotlin Code •Kotlin scratch files •Kotlin REPL •Add a main() function
21. Idiomatic Kotlin Am I doing this right?
22. Useful Syntax
23. Useful Syntax •Use non-null types •Avoid #!! •Use lateinit var •Utility functions without classes
24. Kotlin Standard Library
25. • arrayOf() / listOf() / mapOf() • filter() • map() • orEmpty() • getOrElse() • isNullOrEmpty() / isNullOrBlank() Kotlin Standard Library
26. val awesomeThings = listOf("360AnDev", null, "Kotlin")
27. val awesomeThings = listOf("360AnDev", null, "Kotlin") .filterNotNull()
28. val awesomeThings = listOf("360AnDev", null, "Kotlin") .filterNotNull() .filter { it.length > 6 }
29. val awesomeThing = listOf("360AnDev", null, "Kotlin") .filterNotNull() .filter { it.length > 6 } .getOrElse(0) { "There were no awesome things longer than 6 chars" }
30. val awesomeThing = listOf("360AnDev", null, "Kotlin") .filterNotNull() .filter { it.length > 6 } .getOrElse(0) { "There were no awesome things longer than 6 chars" } .let { AwesomeThing(it) }
31. Special Language Features
32. • Data classes • Sealed classes • Extension functions Special Language Features
33. data class Repo( val name: String, val owner: Owner, val stars: Int ) Data Classes
34. sealed class ViewState { object Loading : ViewState() data class Error(val error: Throwable?) data class Success(val data: List<String>) } Sealed Classes
35. fun Context.longToast(msg: String) { Toast.makeText(this, msg, Toast.LENGTH_LONG).show() } Extension Functions
36. Going Full Kotlin Kotlin all the things!
37. Android Jetpack
38. Android Jetpack •Paging 3 •Benchmark •Android KTX
39. Android KTX
40. Kotlin extensions for Jetpack Leverage Kotlin features •Extension functions/properties •Lambdas •Coroutines Android KTX
41. sharedPreferences.edit { putString(“key”, “with KTX”) putBoolean(“lessBoilerplat”, true) } KTX Core
42. fragmentManager().commit { addToBackstack(“#..”) add(…) } Fragment KTX
43. val viewState: LiveData<ViewState> = liveData { emit(defaultViewState()) } LiveDate KTX
44. @Query(“SELECT * FROM Repos”) suspend fun getRepos(): List<Repo> @Query(“SELECT * FROM Repos”) Fun getRepos(): Flow<List<Repo#>> Room KTX
45. Class RepoListViewModel : ViewModel() { init { viewModelScope.launch { #// load async data } } } ViewModel KTX
46. Kotlin Coroutines
47. Coroutines are the recommended solution for async programming on Android
48. @UiThread suspend fun showTasks() { val tasks = loadTasksFromDisk() displayTasks(tasks) } suspend fun loadTasksFromDisk: List<Task>
49. Class TaskListViewModel : ViewModel() { init { viewModelScope.launch { showTasks() } } }
50. interface TasksApi { @GET(“/tasks/user”) suspend fun loadTasksForUser(id: String) }
51. Class TaskListViewModel : ViewModel() { init { viewModelScope.launch { showTasks() val networkTasks = loadTasksForUser() } } }
52. Kotlin Flow
53. A Flow is an async data stream leveraging coroutines
54. @Query(“SELECT * FROM Repos”) fun getRepos(): Flow<List<Repo#>>
55. val repos: LiveData<List<Repo#>> = repoDao.getRepos().asLiveData()
56. class TaskListViewModel : ViewModel() { private val _viewState = MutableStateFlow(ViewState()) val viewState: StateFlow<ViewState> = _viewState }
57. Gradle Kotlin DSL
58. import org.jetbrains.kotlin.config.KotlinCompilerVersion plugins { id(“com.android.application”) kotlin(“android”) kotlin(“android.extensions”) } android { compileSdkVersion(29) … } dependencies { iplementation(“com.android.support:appcompat-v7:27.1.1”) } build.gradle.kts
59. Jetpack Compose
60. Jetpack Compose is the future of UI development for Android
61. @Composable fun HelloWorld() { Test(“Hello World”) }
62. @Composable fun RepoItem() { Column { Text(“repo name”) Text(“repo owner”) } }
63. class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContent { RepoItem() } } }
64. Bonus • Koin • SQLDelight • Moshi • Coil • MockK
65. Kotlin Beyond Android What else can I build with Kotlin?
66. Kotlin Multiplatform
67. Share core logic across platforms using Kotlin Multiplatform
68. Kotlin Multiplatform Write common Kotlin code Package/Consume for multiple targets •Android/JVM •iOS/MacOS •JavaScript •Native
69. Kotlin Multiplatform Does not replace native UI Relatively low risk for Android
70. Server Side Kotlin
71. Server Side Kotlin Multiple supported frameworks •Ktor •Spring Boot •Quarkus
72. fun main(args: Array<String>) { val server = embeddedServer(Netty, 8080) { routing { get(“/“) { call.respondText(“Hello World!”, ContentType.Text.HTML) } get(“/tasks”) { #// return tasks } } } server.start(wait = true) } Simple Ktor service
73. More Kotlin
74. More Kotlin Additional ways to use Kotlin •JavaScript •Kotlin Native •Kotlin scripting using script
75. Kotlin First
76. Taking Full Advantage of Kotlin Project Samples & Defaults Libraries & Tooling Recommended Language & Patterns Usefulness Beyond Android
77. How do I start? Am I doing this right? I’m convinced I love Kotlin
78. ANDROID DEVELOPER @n8ebel www.goobar.io Nate Ebel Thanks for Watching