Make a weather app with Kotlin (Handson) - DevoxxFR 2017

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#DevoxxFR 1 Grab your stuﬀ ! https://github.com/Ekito/2017-handson-kotlinAndroid Develop a weather app with WIFI : devoxxfr-hol / hola#4321

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#DevoxxFR 2 Develop a weather app with K

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#DevoxxFR Roadmap 3 9:00 - Introduction 9:05 - Intro to Kotlin part 1 9:25 - Project presentation & setup 9:35 - Hands-on part 1 (55 minutes) 10:30 - Coﬀee break 10:45 - Intro to Kotlin part 2 11:00 - Hands-on part 2 (55 minutes) 11:55 - Final Part

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#DevoxxFR 4 @Baresse Work @ ekito Developer & Geek Fullstack & Mobile Laurent BARESSE @arnogiu Work @ ekito Core & Gear Maker Mobile & Cloud Arnaud GIULIANI

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#DevoxxFR Join the team ! 5 https://www.ekito.fr/careers

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#DevoxxFR 6 Mind your vote

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#DevoxxFR 7 Intro to part 1

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#DevoxxFR 8 « production ready » 15.02.2016

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#DevoxxFR 9 Kotlin 1.1.1 @ 15.03.2017

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#DevoxxFR 10 Yet another JVM Language ?

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#DevoxxFR 11 The new « Swift » for Android ?

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#DevoxxFR 12

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#DevoxxFR 13 Kotlin clearly considered by the Java community ! https://spring.io/blog/2017/01/04/introducing-kotlin-support-in-spring-framework-5-0 http://www.javamagazine.mozaicreader.com/ #&pageSet=5&page=0&contentItem=0 (March/April 2017) https://www.thoughtworks.com/radar/languages-and-frameworks/kotlin

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#DevoxxFR 14 - Conciseness & Smarter API - Null Safety & Immutability protection - Type Inference, Static Typing & Smart Casts - Open programming styles - Java Interop Why Kotlin ?

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#DevoxxFR 15 - Fully open source (built by Jetbrains) - Run on Java 6+ - Static typing & type inference - Modern language features - 1st grade tooling What’s Kotlin ?

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#DevoxxFR 16 - String templates - Properties - Lambdas - Data class - Smart cast - Null safety - Lazy property - Default values for function parameters - Extension Functions - No more ; - Single-expression functions - When expression - let, apply, use, with - Collections - Android Extensions Plugin What’s inside Kotlin ?

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#DevoxxFR 17 Compare with Same conciseness and expressive code, but Kotlin static typing and null-safety make a big difference. "Some people say Kotlin has 80% the power of Scala, with 20% of the features" *   "Kotlin is a software engineering language in contrast to Scala which is a computing science language." * Swift and Kotlin are VERY similar. Swift is LLVM based and has C interop while Kotlin is JVM based and has Java interop. * Quotes from Kotlin: The Ying and Yang of Programming Languages @ sdeleuze

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#DevoxxFR 18 is Kotlin Android friendly ? https://github.com/SidneyXu/AndroidDemoIn4Languages Method counts by Language

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#DevoxxFR 19 KOTLIN is not just about writing your app with lesser lines. It’s all about writing SAFER & BETTER APPS !

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#DevoxxFR 20 Let’s Go !

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#DevoxxFR 21 Typing & Inference val a: Int = 1  val b = 1 // `Int` type is inferred var x = 5 // `Int` type is inferred  x += 1 Inferred values Mutable values val : constant value - IMMUTABLE var : variable value - MUTABLE USE VAL AS MUCH AS POSSIBLE !

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#DevoxxFR 22 Safety with Optionals var stringA: String = "foo"  stringA = null //Compilation error - stringA is a String (non optional)    var stringB: String? = "bar" // stringB is an Optional String  stringB = null //ok Optional value

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#DevoxxFR 23 Late initialization, Lazy, Delegates … // set length default value manually  val length = if (stringB != null) stringB.length else -1  //or with the Elvis operator  val length = stringB?.length ?: -1 Default Value & Elvis Operator ?: val length = stringB.length // Compilation error - stringB can be null !  // use ? the safe call operator  val length = stringB?.length //Value or null - length is type Int? val length = stringB!!.length // Value or explicit throw NPE - length is type Int Safe call with ?. or Explicit call with !!.

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#DevoxxFR 24 Example Working with optional values

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#DevoxxFR 25 Example Null check safety & Smart cast Securing with default values

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#DevoxxFR 26 Class class User (  val userName: String,  val ﬁrstName: String,  val lastName: String,  var location: Point? = null  ) POJO + - Getter - Setter - Constructors public / closed by default optional Body

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#DevoxxFR 27 Data Class data class User (  val userName: String,  val ﬁrstName: String,  val lastName: String,  var location: Point? = null  ) POJO + - Getter - Setter - Constructors - toString - hashcode - equals - copy

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#DevoxxFR 28 Pojo ? Kotlin Java

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#DevoxxFR 29 Properties // readonly property  val isEmpty: Boolean  get() = this.size == 0 Properties can be declared in constructor or in class You can also handle getter & setter // customer getter & setter  var stringRepresentation: String set(value) {  … } class ApiKey(var weatherKey: String, var geocodeKey: String){  var debug : Boolean = false  } * Lateinit, Lazy, Delegates …

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#DevoxxFR 30 Object Component // singleton  object Resource {  val name = "Name"  } class StringCalculator{ // class helper  companion object{  val operators = arrayOf("+","-","x","/")  }  } Singleton Class Companion Object

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#DevoxxFR 31 Example data class User(val name: String = "", val age: Int = 0) val jack = User(name = "Jack", age = 1) //no new keyword  val anotherJack = jack.copy(age = 2) Data Class usage A simple GSon Class

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#DevoxxFR 32 When when (s) {  1 -> print("x == 1")  2 -> print("x == 2")  else -> { // Note the block  print("x is neither 1 nor 2")  }  } Flow Control (replace your old if blocks) when (x) {  in 1..10 -> print("x is in the range")  in validNumbers -> print("x is valid")  !in 10..20 -> print("x is outside the range")  else -> print("none of the above")  } Pattern Matching * can match with operators : in, as, is, range …

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#DevoxxFR 33 Example

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#DevoxxFR 34 Collections // immutable map  val map = mapOf("a" to 1, "b" to 2, "c" to 3)  for ((k, v) in map) {  println("$k -> $v")  }   map2["a"] = "my value" // direct map access with array style // range  for (i in 1..100) { //... } // immutable list  val list = listOf("a", "b", "c","aa")  list.ﬁlter { it.startsWith("a") } * collections operators : map, filter, take, flatMap, forEach, firstOrNull, last …

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#DevoxxFR 35 Example Kotlin Collection Java 7 Collection

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#DevoxxFR 36 InterOp Kotlin/Java Java Kotlin

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#DevoxxFR 37 InterOp Java/Kotlin object UserSingleton{  fun stringify(user : User) : String{  // …  }  } fun WhatIsyourAge(user : User){  println("Your age is ${user.age}")  } data class User (val name: String, val age : Int){  companion object{  fun sayHello(user : User){ //…  }  }  } User u = new User("toto",42);  User.Companion.sayHello(u); UserUtilsKt.WhatIsyourAge(u); UserSingleton.INSTANCE.stringify(u)

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#DevoxxFR 38 Project presentation & setup

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#DevoxxFR 39 My Weather app

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#DevoxxFR 40 MainApplication MainActivity DailyForecastModel DialogHelper WeatherSDKUtil WeatherSDK

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#DevoxxFR 41 Get the project https://github.com/Ekito/2017-handson-kotlinAndroid

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#DevoxxFR 42 Create your branch https://github.com/Ekito/2017-handson-kotlinAndroid/blob/master/README.pdf

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#DevoxxFR 43 Adapt the config In app & weathersdk modules: -Android.BuildToolsVersion ~ 24.0.3 -com.android.support ~ 24.1.1 In root build.gradle: -kotlin_version : 1.0.6+ (1.1.1) -retroﬁt_version : 2.1.0+ -okhttp_version : 3.3.1+ In weathersdk module: -rxjava : 1.2.0+ (2.0.5) -rxandroid : 1.1.5 (2.0.1) In root build.gradle: -com.android.tools.build:gradle: 2.2.3 Do not upgrade to Gradle 2.3+ !

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#DevoxxFR 44 Hands-on part 1

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#DevoxxFR 45 9:00 - Introduction 9:05 - Intro to Kotlin part 1 9:25 - Project presentation & setup 9:35 - Hands-on part 1 (55 minutes) 10:30 - Coﬀee break 10:45 - Intro to Kotlin part 2 11:00 - Hands-on part 2 (55 minutes) 11:55 - Final Part Hands-on !

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#DevoxxFR 46 9:00 - Introduction 9:05 - Intro to Kotlin part 1 9:25 - Project presentation & setup 9:35 - Hands-on part 1 (55 minutes) 10:30 - Coﬀee break 10:45 - Intro to Kotlin part 2 11:00 - Hands-on part 2 (55 minutes) 11:55 - Final Part Coffee Break !

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#DevoxxFR 47 Intro to part 2

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#DevoxxFR 48 Sweet stuffs for

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#DevoxxFR 49 Kotlin’s Android Extensions apply plugin: 'com.android.application' apply plugin: ‘kotlin-android’ apply plugin: ‘kotlin-android-extensions’ // if use extensions

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#DevoxxFR 50 Kotlin Java * In Fragment : onViewCreated()

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#DevoxxFR 51 Functions fun reformat(str: String,  normalizeCase: Boolean = true,  upperCaseFirstLetter: Boolean = true,  wordSeparator: Char = ' '): String {    } Named Parameters & default values reformat(str, true, true, '_') // old way to call  reformat(str, wordSeparator = '_') // using default values & named params

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#DevoxxFR 52 Functions Extensions Declaration Usage

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#DevoxxFR 53 Lambdas val fab = findViewById(R.id.fab) as FloatingActionButton  fab.setOnClickListener { view -> popLocationDialog(view) } A lambda expression or an anonymous function is a “function literal”, i.e. a function that is not declared, but passed immediately as an expression - A lambda expression is always surrounded by curly braces - Its parameters (if any) are declared before -> (parameter types may be omitted), - The body goes after -> (when present). myNumber.split("\n").flatMap { it.split(separator) }  .map(Integer::parseInt)  .map(::checkPositiveNumber)  .filter { it <= 1000 }  .sum() * Method references are not surrounded by curly braces

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#DevoxxFR 54 Reactive Programming

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#DevoxxFR 55 Lamba expressions Functional Programming Reactive Streams http://reactivex.io/documentation/operators.html http://www.reactive-streams.org/ https://spring.io/blog/2016/06/07/notes-on-reactive- programming-part-i-the-reactive-landscape

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#DevoxxFR 56 Example - Rx/Retrofit Kotlin Java

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#DevoxxFR 57 Hands-on part 2

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#DevoxxFR 58 9:00 - Introduction 9:05 - Intro to Kotlin part 1 9:25 - Project presentation & setup 9:35 - Hands-on part 1 (55 minutes) 10:30 - Coﬀee break 10:45 - Intro to Kotlin part 2 11:00 - Hands-on part 2 (55 minutes) 11:55 - Final Part Hands-on !