kotlin for android developers

It's an introduction to android but fixing common problems that Android developers have and how to resolve it using kotlin. it's not another kotlin introduction talk.

Transcript

1. Kotlin para Androides Jorge Juan Barroso Carmona jorge@karumi.com @flipper83 Developer Android GDE
2. Sergio Gutierrez Pedro Gomez Davide Mendolia Fran Toro Antonio Lopez
3. Testing for android & iOS. Trainings Architecture, Patterns and principles for Android & iOS. Mastering Git. Advanced mobile development. Testing for android & iOS. Architecture, Patterns and principles for Android & iOS. Companies For Everybody Next open: Testing Training 23 Jun. Kotlin Training 20 Feb. Swift Training 26 Mar. Arch Training 3 Apr.
5. Adam Tornhill “Computer languages differ not so much in what they make possible, but in what they make easy.” Larry Wall
6. https://github.com/Karumi/SuperHeroesKotlin https://github.com/Karumi/KataLogInLogOutKotlin https://github.com/Karumi/KotlinTrainingTeacher
7. Nullability
8. if (user != null && user.email != null) { String email = user.email } Java
9. val email: String? = user?.email Kotlin Is user == null? email is null and the property is never accessed Then email is the user email (that… can be null!) YES NO
10. val email: String? = user?.email ?: "fake@email.com" Is user?.email == null? Then email is “fake@email.com" Then email is the user email YES NO Kotlin Elvis operator
11. val email: String = user!!.email Kotlin Force cast Is user == null? Then NullPointerException is thrown Then email is the user email YES NO
12. Android obtain Views
13. TextView nameView = (TextView) findViewById(R.id.nameView); nameView.setText(“Flipper”); Java
14. import kotlinx.android.synthetic.main.activity_main.* nameView.text = “Flipper” Kotlin
15. Callbacks and High order function
16. TextView nameView = (TextView) findViewById(R.id.nameView); nameView .setOnClickListener((view) -> {doSomething(view)}); Java
17. nameView.setOnClickListener{ doSomething(it) } Kotlin
18. listOf( User(name = “Jane”, age = 45), User(name = “Joe”, age = 23, email = “joe@gmail.com”), User(name = “Jan”, age = 19, email = “jan@gmail.com"), User(name = “J.D.”, age = 66) ).filter { it.email != null } .map {it.email} // [“joe@gmail.com”,"joe@gmail.com"] Kotlin
19. manage async
20. Java AsyncTasks Threads JDeferred RxJava
21. fun doSomethingUsefulOne(): Int { delay(1000L) return 13 } fun doSomethingUsefulTwo(): Int { delay(1000L) return 29 } val time = measureTimeMillis { val one = doSomethingUsefulOne() val two = doSomethingUsefulTwo() println("${one + two}") } println("$time ms”) [“42”, “time 2017”] Kotlin Corrutines suspend fun doSomethingUsefulOne(): Int { delay(1000L) return 13 } suspend fun doSomethingUsefulTwo(): Int { delay(1000L) return 29 } val time = measureTimeMillis { val one = async { doSomethingUsefulOne() } val two = async { doSomethingUsefulTwo() } println("${one.await() + two.await()}") } println("$time ms") [“42”, “time 1017”]
22. Error handling
23. try { User user = repository.getUserById(id); showUser(user); } catch(Exception exception) { showError(exception); } Java
24. val user: Either<Error,User> = repository.getUserById(id); when(user) { is Right -> showUser(it) is Left -> showError(getMessage(it)) } Kotlin val user: Either<Error,User> = repository.getUserById(id); user.fold( isLeft = {showUser(it)}, isRight= {showError(getMessage(it))});
25. fun getMessage(domainError: Error): Int = when (domainError) { is NotInternetDomainError -> R.string.error_not_internet_message is NotIndexFoundDomainError -> R.string.error_superhero_not_found_message is UnknownDomainError -> R.string.error_unknown_message } Kotlin sealed class DomainError object NotInternetDomainError : DomainError() data class UnknownDomainError( val errorMessage: String = "Unknown Error") : DomainError() data class NotIndexFoundDomainError(val key: String) : DomainError() Compile error!!
26. Find me I am very social! jorge@karumi.com @flipper83 What problems do you have with Android?