Kotlin, a nova linguagem oficial do Android
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The document discusses Kotlin as the official language for Android development, highlighting its features such as interoperability, null safety, and conciseness. It provides examples of Kotlin syntax including class definitions, functions, collections, and lambda expressions. Additionally, it showcases the capabilities of Kotlin through various coding techniques and operators.
![GDGFoz
Collections
val set = hashSetOf(1, 2, 3)
val list = arrayListOf(1, 2, 3)
val items = listOf(1, 2, 3, 4)
items.first() == 1
items.last() == 4
items.filter { it % 2 == 0 } // returns [2, 4]
items.forEach { println(it) }
// count, forEachIndexed, max, min, take, slice, map, flatMap
… etc..
// More in https://antonioleiva.com/collection-operations-
kotlin/](https://image.slidesharecdn.com/kotlin-170605125008/85/Kotlin-a-nova-linguagem-oficial-do-Android-17-320.jpg)
Kotlin, a nova linguagem oficial do Android
- 1. Kotlin A nova linguagem oficial do Android
- 2. GDGFoz Quem ? • Houssan Ali Hijazi - hussanhijazi@gmail.com • Desenvolvedor Android na www.HElabs.com • Organizador GDG Foz do Iguaçu • www.lojasnoparaguai.com.br • www.desaparecidosbr.org • www.hussan.com.br
- 3. GDGFoz Kotlin • 2011/JetBrains • 1.0 em Fev. 2016 • 1.1 em Mar. 2017 • Pinterest, Coursera, Netflix, Uber, Square, Trello e Basecamp • Google IO 2017
- 5. GDGFoz Kotlin • Interoperabilidade • Null Safety • Conciso
- 6. GDGFoz Properties/Fields val name: String = "João" val name = "João"
- 7. GDGFoz val/var val user = User() user = User() // :( var user = User() user = User() // :)
- 8. GDGFoz Null Safety/Safe Calls var name: String? = "José" println(name?.length) var name: String = "José" name = null // :( var name: String? = "José" name = null // :) val lastName: String? = null
- 9. GDGFoz Elvis Operator val name: String? = "José" val c: Int = if (name != null) name.length else -1 val c = name?.length ?: -1
- 10. GDGFoz Class class Car(val name: String = ""): Vehicle() { constructor(name: String, color: String) : this(name) { } }
- 11. GDGFoz Kotlin class Car { private String name; public String getName() { //... } public void setName(String s) { //... } } // ^^Java // vv Kotlin val car = Car() println("Name: ${car.name}")
- 12. GDGFoz Functions fun calculate(num: Int, num2: Int = 10): Int { return num + num2 } fun calculate(num: Int, num2: Int): Int = num + num2 fun calculate(num: Int, num2: Int) = num + num2 calculate(num = 10, num2 = 20)
- 13. GDGFoz Interface interface BaseView { fun bar() fun foo() { // optional body } } class View : BaseView { override fun bar() { } }
- 14. GDGFoz Data Class data class Truck(val name:String, val color: String = "Red")
- 15. GDGFoz For/Range // prints number from 1 through 10 for (i in 1..10) { print(i) } // prints 100, 98, 96 ... for (i in 100 downTo 1 step 2) { print(i) } for (item in collection) print(item)
- 16. GDGFoz When when (x) { in 1..10 -> print("x is in the range") !in 10..20 -> print("x is outside the range") else -> print("none of the above") } fun hasPrefix(x: Any) = when(x) { is String -> x.startsWith("prefix") else -> false } when (x) { 1 -> print("x == 1") 2 -> print("x == 2") else -> { print("x is neither 1 nor 2") } }
- 17. GDGFoz Collections val set = hashSetOf(1, 2, 3) val list = arrayListOf(1, 2, 3) val items = listOf(1, 2, 3, 4) items.first() == 1 items.last() == 4 items.filter { it % 2 == 0 } // returns [2, 4] items.forEach { println(it) } // count, forEachIndexed, max, min, take, slice, map, flatMap … etc.. // More in https://antonioleiva.com/collection-operations- kotlin/
- 18. GDGFoz Lambdas showButton.setOnClickListener(new View.OnClickListener() { public void onClick(View button) { text.setVisibility(View.VISIBLE) button.setBackgroundColor(ContextCompat.getColor(this, R.color.colorAccent)) } }); // ^^ Java showButton.setOnClickListener { button -> text.visibility = View.VISIBLE button.setBackgroundColor(ContextCompat.getColor(thi s, R.color.colorAccent)) } // ^^Kotlin
- 19. GDGFoz Lambdas // ^^ Class validate(this::toast) fun validate(callback: () -> Unit) { // validate callback.invoke() } fun toast() { val toast = Toast.makeText(this, "Callback called", Toast.LENGTH_LONG) toast.show() }
- 20. GDGFoz let/with var name: String? = "João" name?.let { println(it.toUpperCase()) println(it.length) } with(name) { println(toUpperCase()) println(length) } // See: apply/run
- 21. GDGFoz Infix infix fun String.drive(car: String) = Pair(this, car) val usersCars = mapOf("José" drive "Fusca", "João" drive "Ferrari") val usersCars2 = mapOf("José".drive("Fusca"), "João".drive("Ferrari")); val (driver, car) = "José" drive "Fusca"
- 22. GDGFoz Extensions fun View.hide() { visibility = View.GONE } fun View.show() { visibility = View.VISIBLE } button.setVisibility(View.VISIBLE) var button: Button = findViewById(R.id.button) as Button button.hide()
- 23. Obrigado