Kotlin

Apresentada na Droid Talks, do Android Meetup Belo Horizonte

Transcript

1. Kotlin turbinando o desenvolvimento Android Rafael Toledo @_rafaeltoledo
2. Kotlin? Baseada na JVM (binding para JavaScript) Linguagem orientada a objetos, com algumas características funcionais Criada pela JetBrains (Android Studio, IntelliJ) Interoperável com Java nas duas vias
3. Data Classes public class User { private String name; private String email; public void setName(String name) { this.name = name; } public String getName() { return name; } }
4. Data Classes data class User(val name: String, val email: String)
5. 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)
6. 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
7. Null Safety ActionBar actionBar = getSupportActionBar(); if (actionBar != null) { actionBar.setTitle("Not so Awesome Java"); }
8. Null Safety supportActionBar?.title = "Awesome Kotlin"
9. Inline methods @Override public int getItemCount() { return items.size(); }
10. Inline methods override fun getItemCount() = items.size
11. Extensions @Override public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { return new ViewHolder(LayoutInflater.from( parent.getContext()).inflate(R.layout.item_list, parent, false)); }
12. Extensions fun ViewGroup.inflate(layoutRes: Int, attachToRoot: Boolean = false): View { return LayoutInflater.from(context).inflate(layoutRes, this, attachToRoot) }
13. Extensions @Override public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { return new ViewHolder(LayoutInflater.from( parent.getContext()).inflate(R.layout.item_list, parent, false)); }
14. Extensions override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) : ViewHolder { return ViewHolder(parent.inflate(R.layout.item_list)) }
15. Extensions 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)
16. Type Alias public class Interceptor implements okhttp3.Interceptor { ... }
17. Type Alias import okhttp3.Interceptor as OkHttpInterceptor ... class Interceptor : OkHttpInterceptor { ... }
18. Singleton public class Singleton { private static final Singleton INSTANCE = new Singleton(); public static Singleton getInstance() { return INSTANCE; } private Singleton() { } }
19. Singleton object Singleton { ... }
20. Lambdas public interface Callback { void onFinish(Result result); } public void asyncRequest(Callback callback) { ... callback.onFinish(result); }
21. Lambdas asyncRequest(new Callback() { @Override public void onFinish(Result result) { Log.i("Callback", "Result was " + result.status()); } });
22. Lambdas asyncRequest(result -> Log.i("Callback", "Result was " + result.status())); // Depende de Retrolambda ou Jack
23. Lambdas fun asyncRequest(callback: (Result) -> Unit) { ... callback(result) } asyncRequest { result -> Log.i("Callback", "Result was ${result.status()}") }
24. Lambdas fun asyncRequest(callback: (Result) -> Unit) { ... callback(result) } asyncRequest { Log.i("Callback", "Result was ${it.status()}") }
25. anko extensões e dsl
26. Assincronismo e UI Thread ... doAsync() { val result = api.fetchData() // Sync call uiThread { textView.text = result.data } }
27. Intents Intent intent = new Intent(context, AnotherActivity.class); intent.putExtra("id", 1); intent.setFlag(Intent.FLAG_ACTIVITY_SINGLE_TOP); context.startActivity(intent);
28. Intents ctx.startActivity(intentFor<AnotherActivity>("id" to 1) .singleTop()) makeCall("1406") browse("https://google.com") email("foo@bar.com", "Subject", "Body")
29. Toasts & Log toast("Hello") toast(R.string.hello) longToast("Hello again, because this toast is so long") info("Hello") warn(0) debug("Another log")
30. Kotlin Android Extension 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!") }
31. não tão legal... alguns pontos de estranheza
32. Companion Objects public class MyAwesomeClass { public static final String CONSTANT_VALUE = "X"; }
33. Companion Objects class MyAwesomeClass { companion object { val CONSTANT_VALUE = "X" } }
34. Interoperabilidade retrofit.create(MyApiInterface::class.java) @Rule @JvmField val activityRule = ActivityTestRule<MainActivity>( MainActivity::class.java)
35. Dex Limit Total methods in app-debug.apk: 35032 (53,46% used) Total fields in app-debug.apk: 15760 (24,05% used) Methods remaining in app-debug.apk: 30503 Fields remaining in app-debug.apk: 49775
36. Dex Limit - Shrinker / Proguard Total methods in app-debug.apk: 15315 (23,37% used) Total fields in app-debug.apk: 8238 (12,57% used) Methods remaining in app-debug.apk: 50220 Fields remaining in app-debug.apk: 57297
37. Parcelable data class User(val name: String, val email: String)
38. Parcelable data class User(val name: String, val email: String) : Parcelable { constructor(parcel: Parcel) : this(parcel.readString(), parcel.readString()) override fun writeToParcel(dest: Parcel?, flags: Int) { dest?.writeString(name) dest?.writeString(email) } override fun describeContents() = 0 companion object { val CREATOR: Parcelable.Creator<User> = object: Parcelable.Creator<User> { override fun createFromParcel(parcel: Parcel) = User(parcel) override fun newArray(size: Int): Array<User?> = arrayOfNulls(size) } } }
39. Outros Ausência de linters Tempo de build (pouco) maior Cobertura de código para CI Ofuscação?
40. kotlin 1.1 o que vem por aí
41. Coroutines fun loadUser(id: Int) = async { // getUser() retorna um CompletableFuture - API 24 :( val user = api.getUser(id).await() textView.text = user.name }
42. Underscores para parâmetros fun loadProduct(id: Int) { api.fetchProduct(id) { (_, name, date) -> title.text = name createdOn.text = date.format() } }
43. Type Alias typealias Lenght = Double typealias Action<T> = (T) -> Unit typealias Multimap<K, V> = Map<K, List<V>>
44. 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
45. Livros Kotlin for Android Developers leanpub.com/kotlin-for-android-developers Kotlin in Action www.manning.com/books/kotlin-in-action Experimentos Kotlin Sandbox github.com/rafaeltoledo/kotlin-sandbox
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