Develop a weather app with Kotlin (DevoxxFR 17)

Hands-on DevoxxFR 2017

Transcript

1. #DevoxxFR 2 Develop a weather app with K
2. #DevoxxFR 1 Grab your stuff ! https://github.com/Ekito/2017-handson-kotlinAndroid Develop a weather app with WIFI : devoxxfr-hol / hola#4321
3. #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
4. #DevoxxFR 4 @Baresse Work @ ekito Developer & Geek Fullstack & Mobile Laurent BARESSE @arnogiu Work @ ekito Core & Gear Maker Mobile & Cloud Arnaud GIULIANI
5. #DevoxxFR Join the team ! 5 https://www.ekito.fr/careers
6. #DevoxxFR 6 Mind your vote
7. #DevoxxFR 7 Intro to part 1
8. #DevoxxFR 8 « production ready » 15.02.2016
9. #DevoxxFR 9 Kotlin 1.1.1 @ 15.03.2017
10. #DevoxxFR 10 Yet another JVM Language ?
11. #DevoxxFR 11 The new « Swift » for Android ?
12. #DevoxxFR 12
13. #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
14. #DevoxxFR 14 - Conciseness & Smarter API - Null Safety & Immutability protection - Type Inference, Static Typing & Smart Casts - Open programming styles - Java Interop Why Kotlin ?
15. #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 ?
16. #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 ?
17. #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
18. #DevoxxFR 18 is Kotlin Android friendly ? https://github.com/SidneyXu/AndroidDemoIn4Languages Method counts by Language
19. #DevoxxFR 19 KOTLIN is not just about writing your app with lesser lines. It’s all about writing SAFER & BETTER APPS !
20. #DevoxxFR 20 Let’s Go !
21. #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 !
22. #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
23. #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 !!.
24. #DevoxxFR 24 Example Working with optional values
25. #DevoxxFR 25 Example Null check safety & Smart cast Securing with default values
26. #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
27. #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
28. #DevoxxFR 28 Pojo ? Kotlin Java
29. #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 …
30. #DevoxxFR 30 Object Component // singleton
 object Resource {
 val name = "Name"
 } class StringCalculator{ // class helper
 companion object{
 val operators = arrayOf("+","-","x","/")
 }
 } Singleton Class Companion Object
31. #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
32. #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 …
33. #DevoxxFR 33 Example
34. #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 …
35. #DevoxxFR 35 Example Kotlin Collection Java 7 Collection
36. #DevoxxFR 36 InterOp Kotlin/Java Java Kotlin
37. #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)
38. #DevoxxFR 38 Project presentation & setup
39. #DevoxxFR 39 My Weather app
40. #DevoxxFR 40 MainApplication MainActivity DailyForecastModel DialogHelper WeatherSDKUtil WeatherSDK
41. #DevoxxFR 41 Get the project https://github.com/Ekito/2017-handson-kotlinAndroid
42. #DevoxxFR 42 Create your branch https://github.com/Ekito/2017-handson-kotlinAndroid/blob/master/README.pdf
43. #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+ !
44. #DevoxxFR 44 Hands-on part 1
45. #DevoxxFR 45 9:30 - Introduction 9:35 - Intro to Kotlin part 1 9:55 - Project presentation & setup 10:05 - Hands-on part 1 (55 minutes) 11:00 - Coffee break 11:15 - Intro to Kotlin part 2 11:30 - Hands-on part 2 (55 minutes) 12:25 - Final Part Hands-on !
46. #DevoxxFR 46 9:30 - Introduction 9:35 - Intro to Kotlin part 1 9:55 - Project presentation & setup 10:05 - Hands-on part 1 (55 minutes) 11:00 - Coffee break 11:15 - Intro to Kotlin part 2 11:30 - Hands-on part 2 (55 minutes) 12:25 - Final Part Coffee Break !
47. #DevoxxFR 47 Intro to part 2
48. #DevoxxFR 48 Sweet stuffs for
49. #DevoxxFR 49 Kotlin’s Android Extensions apply plugin: 'com.android.application' apply plugin: ‘kotlin-android’ apply plugin: ‘kotlin-android-extensions’ // if use extensions
50. #DevoxxFR 50 Kotlin Java * In Fragment : onViewCreated()
51. #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
52. #DevoxxFR 52 Functions Extensions Declaration Usage
53. #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
54. #DevoxxFR 54 Reactive Programming
55. #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
56. #DevoxxFR 56 Example - Rx/Retrofit Kotlin Java
57. #DevoxxFR 57 Hands-on part 2
58. #DevoxxFR 58 9:30 - Introduction 9:35 - Intro to Kotlin part 1 9:55 - Project presentation & setup 10:05 - Hands-on part 1 (55 minutes) 11:00 - Coffee break 11:15 - Intro to Kotlin part 2 11:30 - Hands-on part 2 (55 minutes) 12:25 - Final Part Hands-on !
59. #DevoxxFR 59 Final Part
60. #DevoxxFR 60 Time is over !
61. #DevoxxFR 61 Smarter development for the JVM Kotlin
62. #DevoxxFR 62 Mind your vote
63. #DevoxxFR Thank you for coming 63