Kotlin is here

Intro to Kotlin.
Google IO Extended Cebu

Transcript

1. Kotlin is here Too much fun
7. .java java compiler .class .jar dex
8. .kt .java java compiler .class .jar dex kotlin compiler
9. class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) }
10. class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) }
11. class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) }
12. class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) }
13. override fun onResume() { super.onResume() mAutofillManager?.registerCallback(mAutofillCallback) } override fun onPause() { super.onPause() mAutofillManager?.unregisterCallback(mAutofillCallback) }
15. var index = structure.addChildCount(chidrenSize) val context : Context = request.getContext() Variables
16. var index = structure.addChildCount(chidrenSize) val context : Context = request.getContext() Variables
17. var index = structure.addChildCount(chidrenSize) val context : Context = request.getContext() Variables
18. var index = structure.addChildCount(chidrenSize) val context : Context = request.getContext() Variables var index : Int = structure.addChildCount(chidrenSize)
19. var textValue : String = "" textValue = "alo" var index = structure.addChildCount(chidrenSize) val context : Context = request.getContext() Variables
20. var textValue : String = "" textValue = "alo" var index = structure.addChildCount(chidrenSize) val context : Context = request.getContext() Variables val textValue : String = "" textValue = "alo"
21. var textValue : String = "" textValue = "alo" var index = structure.addChildCount(chidrenSize) val context : Context = request.getContext() Variables val textValue : String = "" textValue = "alo"
22. class SimpleClass Classes/Objects
23. class SimpleClass open class SimpleClass Classes/Objects
24. class SimpleClass open class SimpleClass class SimpleClass : BaseClass() Classes/Objects
25. class SimpleClass open class SimpleClass class SimpleClass : BaseClass() class SimpleClass : SimpleInterface Classes/Objects
26. class SimpleClass open class SimpleClass class SimpleClass : BaseClass() class SimpleClass : SimpleInterface object SimpleClass Classes/Objects
27. class SimpleClass(value: String) Classes/Objects
28. class SimpleClass(value: String) Classes/Objects class Team { val player : String var goals : Int }
29. class SimpleClass(value: String) Classes/Objects class Team { val player : String var goals : Int }
30. class SimpleClass(value: String) Classes/Objects class Team { val player : String = “Rivaldo” var goals : Int = 0 }
31. class SimpleClass(value: String) Classes/Objects val myPlayer = Team(“Rivaldo”,0) class Team(player: String, goals: Int)
32. class SimpleClass(value: String) Classes/Objects val myPlayer = Team(“Rivaldo”,0) class Team(player: String) { var goals: Int = 0 } class Team(player: String, goals: Int)
33. class SimpleClass(value: String) Classes/Objects val myPlayer = Team(“Rivaldo”,0) class Team(player: String) { var goals: Int = 0 } val myPlayer = Team("Rivaldo") myPlayer.goals = 3 class Team(player: String, goals: Int)
34. Classes/Objects var goals: Int = 0 set(value) { if (goals > 5) { log(“$player has scored multiple goals") field = value } }
35. Classes/Objects var goals: Int = 0 set(value) { if (goals > 5) { log(“$player has scored multiple goals") field = value } } val isEmpty get() = this.size == 0
36. class SimpleClass(value: String){ init { log() } } Classes/Objects
37. class SimpleClass(value: String){ init { log() } } Classes/Objects class Button : View { constructor(ctx: Context) : super(ctx) constructor(ctx: Context, attr: AttributeSet) : super(ctx, attr) }
38. Classes/Objects data class Team (val name : String, val goals : Int)
39. Classes/Objects data class Team (val name : String, val goals : Int) hashCode - toString - equals
40. Classes/Objects class A { companion object { fun bar() { println("Companion Object") } } } data class Team (val name : String, val goals : Int) hashCode - toString - equals
41. Classes/Objects class A { companion object { fun bar() { println("Companion Object") } } } data class Team (val name : String, val goals : Int) hashCode - toString - equals A.bar()
42. Smart Casts public void printTypeProperty(Object object) { if (object instanceof String) { System.out.print(((String) object).isEmpty()); } else if (object instanceof Integer){ System.out.print(((Integer) object).intValue()); } else if (object instanceof Boolean){ System.out.print(((Boolean) object).booleanValue()); } }
43. fun printTypeProperty(any: Any) { if (any is String) { println(any.length) } else if (any is Int) { println(any.plus(1)) } else if (any is Boolean) { println(any.not()) } } Smart Casts public void printTypeProperty(Object object) { if (object instanceof String) { System.out.print(((String) object).isEmpty()); } else if (object instanceof Integer){ System.out.print(((Integer) object).intValue()); } else if (object instanceof Boolean){ System.out.print(((Boolean) object).booleanValue()); } }
44. fun printTypeProperty(any: Any) { if (any is String) { println(any.length) } else if (any is Int) { println(any.plus(1)) } else if (any is Boolean) { println(any.not()) } } Smart Casts public void printTypeProperty(Object object) { if (object instanceof String) { System.out.print(((String) object).isEmpty()); } else if (object instanceof Integer){ System.out.print(((Integer) object).intValue()); } else if (object instanceof Boolean){ System.out.print(((Boolean) object).booleanValue()); } }
45. sealed class Expr data class Const(val number: Double) : Expr() data class Sum(val e1: Expr, val e2: Expr) : Expr() object NotANumber : Expr() Sealed Classes
46. sealed class Expr data class Const(val number: Double) : Expr() data class Sum(val e1: Expr, val e2: Expr) : Expr() object NotANumber : Expr() Sealed Classes
47. sealed class Expr data class Const(val number: Double) : Expr() data class Sum(val e1: Expr, val e2: Expr) : Expr() object NotANumber : Expr() Sealed Classes
48. sealed class Expr data class Const(val number: Double) : Expr() data class Sum(val e1: Expr, val e2: Expr) : Expr() object NotANumber : Expr() fun eval(expr: Expr): Double = when(expr) { is Const -> expr.number is Sum -> eval(expr.e1) + eval(expr.e2) NotANumber -> Double.NaN } Sealed Classes
49. sealed class Expr data class Const(val number: Double) : Expr() data class Sum(val e1: Expr, val e2: Expr) : Expr() object NotANumber : Expr() fun eval(expr: Expr): Double = when(expr) { is Const -> expr.number is Sum -> eval(expr.e1) + eval(expr.e2) NotANumber -> Double.NaN } Sealed Classes
50. sealed class Expr data class Const(val number: Double) : Expr() data class Sum(val e1: Expr, val e2: Expr) : Expr() object NotANumber : Expr() fun eval(expr: Expr): Double = when(expr) { is Const -> expr.number is Sum -> eval(expr.e1) + eval(expr.e2) NotANumber -> Double.NaN } Sealed Classes
51. Interfaces class SimpleClass : SimpleInterface
52. interface SimpleInterface { fun doSomething() } Interfaces class SimpleClass : SimpleInterface
53. interface SimpleInterface { fun doSomething() } interface SimpleInterface { fun doSomething() fun doAnotherThing() = println("default") } Interfaces class SimpleClass : SimpleInterface
54. int strLen(String s){ return s.length(); } Nullability
55. fun strLen(s: String) = s.length int strLen(String s){ return s.length(); } Nullability
56. fun strLen(s: String) = s.length int strLen(String s){ return s.length(); } fun strLen(s: String?) = … Nullability
57. fun strLen(s: String) = s.length int strLen(String s){ return s.length(); } fun strLen(s: String?) = … fun strLen(s: String?): Int = if (s != null) s.length else 0 Nullability
58. fun toUpperCase(s: String?): String? Nullability
59. fun toUpperCase(s: String?): String? fun toUpperCase(s: String?): String? = s?.toUpperCase() Nullability
60. fun toUpperCase(s: String?): String? fun toUpperCase(s: String?): String? = s?.toUpperCase() Nullability
61. fun toUpperCase(s: String?): String? fun toUpperCase(s: String?): String? = s?.toUpperCase() fun length(s: String?): Int Nullability
62. fun toUpperCase(s: String?): String? fun toUpperCase(s: String?): String? = s?.toUpperCase() fun length(s: String?): Int fun length(s: String?): Int = s?.length ?: 0 Nullability
63. fun toUpperCase(s: String?): String? fun toUpperCase(s: String?): String? = s?.toUpperCase() fun length(s: String?): Int fun length(s: String?): Int = s?.length ?: 0 Nullability
64. fun toUpperCase(s: String?): String? fun toUpperCase(s: String?): String? = s?.toUpperCase() fun length(s: String?): Int fun length(s: String?): Int = s?.length ?: 0 Nullability
65. this as? PageObjectKt Nullability
66. this as? PageObjectKt Nullability email?.let { email -> sendEmailTo()}
67. fun max(a: Int, b: Int): Int { return if (a > b) a else b } Functions
68. fun max(a: Int, b: Int): Int { return if (a > b) a else b } Functions
69. fun max(a: Int, b: Int): Int { return if (a > b) a else b } Functions
70. fun max(a: Int, b: Int): Int { return if (a > b) a else b } Functions
71. fun createPlayer(name: String, lastName: String, nickName: String?, city: String?) { Functions - Named Arguments
72. fun createPlayer(name: String, lastName: String, nickName: String?, city: String?) { createPlayer("Inaki", "Villar", null, null) Functions - Named Arguments
73. fun createPlayer(name: String, lastName: String, nickName: String?, city: String?) { createPlayer("Inaki", "Villar", null, null) createPlayer("Inaki", "Villar", nickName = null, city = null) Functions - Named Arguments
74. fun createPlayer(name: String, lastName: String, nickName: String = “", city: String = "Cebu") Functions - Default Arguments
75. fun createPlayer(name: String, lastName: String, nickName: String = “", city: String = "Cebu") createPlayer("Inaki", "Villar") Functions - Default Arguments createPlayer("Inaki", "Villar", "Nine")
76. fun lengthIsGreaterThanFive(s : String) = s.length > 5 val va = "myVeryLongString" val isGreaterThanFive = lengthIsGreaterThanFive(va) Extension Functions
77. fun lengthIsGreaterThanFive(s : String) = s.length > 5 val va = "myVeryLongString" val isGreaterThanFive = lengthIsGreaterThanFive(va) Extension Functions fun String.lengthIsGreaterThanFive() = this.length > 5
78. fun lengthIsGreaterThanFive(s : String) = s.length > 5 val va = "myVeryLongString" val isGreaterThanFive = lengthIsGreaterThanFive(va) Extension Functions fun String.lengthIsGreaterThanFive() = this.length > 5
79. fun lengthIsGreaterThanFive(s : String) = s.length > 5 val va = "myVeryLongString" val isGreaterThanFive = lengthIsGreaterThanFive(va) val va = "myVeryLongString" val isGreaterThanFive = va.lengthIsGreaterThanFive() Extension Functions fun String.lengthIsGreaterThanFive() = this.length > 5
80. Infix Functions infix fun Int.minus(value: Int) = this - value
81. Infix Functions infix fun Int.minus(value: Int) = this - value
82. Infix Functions infix fun Int.minus(value: Int) = this - value val result = 4 minus 2
83. Infix Functions infix fun Int.minus(value: Int) = this - value val result = 4 minus 2
84. Infix Functions infix fun Int.minus(value: Int) = this - value val result = 4 minus 2 4.minus(2)
85. Infix Functions infix fun Int.minus(value: Int) = this - value val result = 4 minus 2 infix fun String.repeat(times: Int) = { var result = "" for (i in 1..times) { result += this } }
86. Infix Functions infix fun Int.minus(value: Int) = this - value val result = 4 minus 2 infix fun String.repeat(times: Int) = { var result = "" for (i in 1..times) { result += this } }
87. Infix Functions infix fun Int.minus(value: Int) = this - value val result = 4 minus 2 infix fun String.repeat(times: Int) = { var result = "" for (i in 1..times) { result += this } } val multipleA = "a" repeat 10
88. Lambdas
89. buttonSend.setOnClickListener(new View.OnClickListener(){ @Override public void onClick(View v){ send(); } }); Lambdas
90. buttonSend.setOnClickListener(new View.OnClickListener(){ @Override public void onClick(View v){ send(); } }); buttonSend.setOnClickListener(object :OnClickListener{ override fun onClick(view : View){ send(); } }) Lambdas
91. buttonSend.setOnClickListener(new View.OnClickListener(){ @Override public void onClick(View v){ send(); } }); buttonSend.setOnClickListener(object :OnClickListener{ override fun onClick(view : View){ send(); } }) buttonSend.setOnClickListener(View.OnClickListener { view : View -> doSomething() }) Lambdas
92. { x : Int, y: Int -> x + y } Lambdas
93. { x : Int, y: Int -> x + y } Lambdas
94. { x : Int, y: Int -> x + y } Lambdas
95. data class Team (val name : String, val goals : Int) val myLeague = listOf(Team("Sakuvic", 12), Team("Rivaldo",10)) Lambdas
96. data class Team (val name : String, val goals : Int) val myLeague = listOf(Team("Sakuvic", 12), Team("Rivaldo",10)) myLeague.maxBy({ p: Team -> p.goals }) Lambdas
97. data class Team (val name : String, val goals : Int) val myLeague = listOf(Team("Sakuvic", 12), Team("Rivaldo",10)) myLeague.maxBy({ p: Team -> p.goals }) myLeague.maxBy { p: Team -> p.goals } Lambdas
98. myLeague.maxBy { it.goals } data class Team (val name : String, val goals : Int) val myLeague = listOf(Team("Sakuvic", 12), Team("Rivaldo",10)) myLeague.maxBy({ p: Team -> p.goals }) myLeague.maxBy { p: Team -> p.goals } Lambdas
100. private val mOnNavigationItemSelectedListener = BottomNavigationView.OnNavigationItemSelectedListener { item -> when (item.itemId) { R.id.navigation_home -> { message.setText(R.string.title_home) return@OnNavigationItemSelectedListener true } R.id.navigation_dashboard -> { message.setText(R.string.title_dashboard) return@OnNavigationItemSelectedListener true } R.id.navigation_notifications -> { message.setText(R.string.title_notifications) return@OnNavigationItemSelectedListener true } } false Future is here
101. Much more Type System Delegation High Order Functions & FP Operator Generics DSL
103. inaki.seri@gmail.com @inyaki_mwc Thanks