Kotlin - Turbinando o Desenvolvimento Android

Apresentada no Google Launchpad Build Recife 2017

Transcript

1. KOTLIN Turbinando o Desenvolvimento Android Rafael Toledo @_rafaeltoledo
2. POR QUÊ?
3. JETBRAINS INICIADA EM 2010 PELA é uma linguagem de programação segura e acessível além de ser muito pragmática
4. O QUE É? •Estaticamente tipada •Inspirada por Java, Scala, C#, Groovy •Targets: •JVM / Android •JavaScript •Nativo
5. LINHAS DE CÓDIGO EM KOTLIN no Github
6. GOOGLE I/O 2017
7. APLICAÇÕES • Mobile • Client Side •Web •Desktop • Server Side
8. BENEFÍCIOS • Familiaridade com C#, Java, JavaScript, facilitando a adoção • Interoperabilidade com a plataforma • Java - JVM • JavaScript • Nativo - Interoperabilidade com C
9. CONVENÇÕES • Segue as convenções de código do Java • Tipos em caixa alta - MeuTipo • Métodos e Properties em caixa baixa camelCase • Ponto e vírgula opcional* • Pacotes seguem a notação reversa • Múltiplas classes por arquivo são permitidas • Pacotes não precisam seguir a estrutura de pastas
10. FERRAMENTAL • JDK •Versão 6, 7, 8 e 9 • Compilador Kotlin • Editor ou IDE • IntelliJ IDEA, Android Studio, Netbeans, Eclipse
11. CARACTERÍSTICAS
12. DATA CLASSES public class User { private String name; private String email; public void setName(String name) { this.name = name; } public String getName() { return name; } }
13. DATA CLASSES data class User(val name: String, val email: String)
14. MÚLTIPLAS CLASSES POR ARQUIVO data class User(val name: String, val email: String) data class Order(val id: Int, val user: User) data class Address(val street: String)
15. PROPERTIES var simple: Int? val inferredType = 1 val isEmpty: Boolean get() = this.size == 0 var stringValue: String get() = this.toString() set(value) { splitAndAssign(value) } var privateSetter: String = "a" private set var annotated: Any? = null @Inject set
16. NULL SAFETY ActionBar actionBar = getSupportActionBar(); if (actionBar != null) { actionBar.setTitle("Not so Awesome Java"); }
17. NULL SAFETY supportActionBar?.title = "Awesome Kotlin"
18. MÉTODOS INLINE @Override public int getItemCount() { return items.size(); }
19. MÉTODOS INLINE override fun getItemCount() = items.size
20. COMPANION OBJECT public class MyAwesomeClass { public static final String CONSTANT_VALUE = "X"; }
21. COMPANION OBJECT class MyAwesomeClass { companion object { val CONSTANT_VALUE = "X" } }
22. EXTENSÕES @Override public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { return new ViewHolder(LayoutInflater.from( parent.getContext()).inflate(R.layout.item_list, parent, false)); }
23. EXTENSÕES fun ViewGroup.inflate(layoutRes: Int, attachToRoot: Boolean = false): View { return LayoutInflater.from(context).inflate(layoutRes, this, attachToRoot) }
24. EXTENSÕES @Override public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { return new ViewHolder(LayoutInflater.from( parent.getContext()).inflate(R.layout.item_list, parent, false)); }
25. EXTENSÕES override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder { return ViewHolder(parent.inflate(R.layout.item_list)) }
26. EXTENSÕES override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder { return ViewHolder(parent.inflate(R.layout.item_list)) } parent.inflate(R.layout.item_list) parent.inflate(R.layout.item_list, false) // Mesma coisa parent.inflate(R.layout.item_list, true)
27. TYPE ALIAS public class Interceptor implements okhttp3.Interceptor { ... }
28. TYPE ALIAS import okhttp3.Interceptor as OkHttpInterceptor ... class Interceptor: OkHttpInterceptor { ... }
29. SINGLETON public class Singleton { private static final Singleton INSTANCE = new Singleton(); public static Singleton getInstance() { return INSTANCE; } private Singleton() { } }
30. SINGLETON object Singleton { ... }
31. LAMBDAS public interface Callback { void onFinish(Result result); } public void asyncRequest(Callback callback) { ... callback.onFinish(result); }
32. LAMBDAS asyncRequest(new Callback() { @Override public void onFinish(Result result) { Log.i("Callback", "Result was " + result.status()); } });
33. LAMBDAS asyncRequest(result -> Log.i("Callback", "Result was " + result.status())); // Depende de Retrolambda, Jack (plugin 2.x) ou plugin 3.+
34. LAMBDAS fun asyncRequest(callback: (Result) -> Unit) { ... callback(result) } asyncRequest { result -> Log.i("Callback", "Result was ${result.status()}") }
35. LAMBDAS fun asyncRequest(callback: (Result) -> Unit) { ... callback(result) } asyncRequest { Log.i("Callback", "Result was ${it.status()}") }
36. LAMBDA - PARÂMETROS NÃO UTILIZADOS fun loadProduct(id: Int) { api.fetchProduct(id) { (_, name, date) -> title.text = name createdOn.text = date.format() } }
37. TYPE ALIAS typealias Length = Double typealias Weight = Double typealias Action<T> = (T) -> Unit typealias Multimap<K, V> = Map<K, List<V>>
38. DESESTRUTURANDO CLASSES data class User(val username: String, val email: String) fun printUserData() { val (username, email) = fetchUser() println("${username}: ${email}") }
39. INTEROPERABILIDADE COM JAVA retrofit.create(MyApiInterface::class.java) @Rule @JvmField val activityRule = ActivityTestRule<MainActivity>( MainActivity::class.java)
40. COROUTINES - EXPERIMENTAL • Código assíncrono com cara de síncrono • É basicamente uma "thread" (só que bem mais leve) que é pausada e retomada posteriormente "We think that now we have got a great design of coroutines for Kotlin, but we realize that it has not been battle-tested enough."
41. COROUTINES kotlin { experimental { coroutines 'enable' } }
42. COROUTINES fun someWork(): CompletableFuture<String> = ... fun moreWork() = async { println("Work started") val str = await(someWork()) println("Work completed") }
43. COROUTINES fun someWork(): CompletableFuture<String> = ... // CompletableFuture = minSdkVersion 24 fun moreWork() = async { println("Work started") val str = await(someWork()) println("Work completed") }
44. COROUTINES fun someWork(): CompletableFuture<String> = ... // CompletableFuture = minSdkVersion 24 fun moreWork() = async { println("Work started") val str = await(someWork()) println("Work completed") }
45. COROUTINES - EXPERIMENTAL github.com/kotlin/kotlinx.coroutines Documentação Extensões e utilitários para Java 8, NIO (Java 7), Swing, JavaFX e RxJava
46. ANKO extensões e DSL
47. ASSINCRONISMO E UI THREAD ... doAsync { val result = api.fetchData() // Sync call uiThread { textView.text = result.data } }
48. INTENTS Intent intent = new Intent(context, AnotherActivity.class); intent.putExtra("id", 1); intent.setFlag(Intent.FLAG_ACTIVITY_SINGLE_TOP); context.startActivity(intent);
49. INTENTS ctx.startActivity(intentFor<AnotherActivity>("id" to 1) .singleTop()) makeCall("1406") browse("https://google.com") email("foo@bar.com", "Subject", "Body")
50. TOAST & LOG toast("Hello") toast(R.string.hello) longToast("Hello again, because this toast is so long") info("Hello") warn(0) debug("Another log")
51. ANDROID EXTENSIONS mais um pouco de comodidade pro Android
52. ANDROID EXTENSIONS Adeus ao findViewById() import kotlinx.android.synthetic.main.activity_main.* ... override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContextView(R.layout.activity_main) textView.setText("It's a kind of magic!") }
53. REFERÊNCIAS & LINKS Blog Oficial blog.jetbrains.com/kotlin anko github.com/kotlin/anko Blog do Antonio Leiva antonioleiva.com Kotlin Koans kotlinlang.org/docs/tutorials/koans.html
54. REFERÊNCIAS & LINKS Livro: Kotlin for Android Developers leanpub.com/kotlin-for-android-developers Livro: Kotlin in Action manning.com/books/kotlin-in-action Kotlin Sandbox github.com/rafaeltoledo/kotlin-sandbox
55. OBRIGADO! Rafael Toledo @_rafaeltoledo