Filipe Guedes e Philipe Steiff, 99 Taxi, falam sobre Live code with Kotlin: construindo o primeiro app usando Kotlin no Android DevConference 2016. Saiba mais em: http://androidconference.com.br/

1. Construindo o primeiro app
usando Kotlin
Filipe Guedes Philipe Steiff
@fgsguedes @philipesteiff

2. Por que Kotlin?
• Concisa, simples e fácil de ler/escrever
• 100% "two-way" interoperável com Java
• Também é funcional
• Null-safety
• Extension functions
• It's fun

3. class Foo {
fun sum(a: Int, b: Int): Int {
return a + b
}
fun printSum(a: Int, b: Int): Unit {
print(a + b)
}
}

4. class Foo {
fun sum(a: Int, b: Int) = a + b
fun printSum(a: Int, b: Int) {
print(a + b)
}
}

5. val a: Int = 1
val b = 1
var c = "Any variable"
val d = Foo()

6. Null Safety
var a: String = "abc"

7. Null Safety
var a: String = "abc"
a = null

8. Null Safety
var a: String = "abc"
a = null // compilation error

9. Null Safety
var a: String = "abc"
a = null // compilation error
println(a.length)

10. Null Safety
var a: String? = "abc"
a = null
println(a.length)

11. Null Safety
var a: String? = "abc"
a = null
println(a.length)
// compilation error

12. Null Safety
var a: String? = "abc"
a = null
println(a?.length)

13. Null Safety
var a: String? = "abc"
a = null
println(a?.length)
// will print 'null'

14. Null Safety
var a: String? = "abc"
a = null
println(a?.length ?: "Was null")
// will print 'Was null'

15. Null Safety
var a: String? = "abc"
a = null
println(a!!.length)
// XGH

16. Extensions
fun Parcel.readBoolean() = readByte() > 0
fun Parcel.writeBoolean(boolean: Boolean) {
when {
boolean -> writeByte(1)
else -> writeByte(0)
}
}
override fun writeToParcel(parcel: Parcel, p1: Int) {
parcel.writeBoolean(myBooleanField)
}
myBooleanField = parcel.readBoolean()

17. Quem está usando!?

18. Some live coding!!
Wish us luck