Kotlin for Android - A first approach

A first approach to Android Development using Kotlin as a main language. This presentation was part of the first Kotlin Night Meetup held in Vancouver, Canada - https://www.meetup.com/es-ES/VancouverKotlin/events/238810235/

Transcript

1. Kotlin for Android A first approach Carlos Daniel Munoz - Android Dev @cdmunozi cdmunoz@gmail.com Co-Founder & Co-Organizer @MedellinAndroid May 23 VANCOUVER’S KOTLIN NIGTH #1
2. Why Kotlin in Android?
3. 3 Java in Android
4. 4 Java in Android • Java 6.5 (Dic. 2006)
5. 5 Java in Android • Java 6.5 (Dic. 2006) • Some hard to avoid limitations: Compatibility with past versions of Android
6. 6 Java in Android • Java 6.5 (Dic. 2006) • Some hard to avoid limitations: Compatibility with past versions of Android • “Compatibility” with some Java 8 features ◦ Virtual Machine Java 6 :( ◦ Not ready to support Java 8
7. 7 Java in Android • Java 6.5 (Dic. 2006) • Some hard to avoid limitations: Compatibility with past versions of Android • “Compatibility” with some Java 8 features ◦ Virtual Machine Java 6 :( ◦ Not ready to support Java 8 • Java 8 is limited, compared to other modern languages
8. 8 Problems with Java • Are we safe with nulls? ◦ This compiles perfectly
9. 9 Problems with Java • Are we safe with nulls? ◦ This compiles perfectly
10. 10 Problems with Java • Immutability not well implemented
11. 11 Problems with Java • Immutability not well implemented ◦ Variables can be modified easily
12. 12 Problems with Java • Immutability not well implemented ◦ Variables can be modified easily ◦ “Race condition” → who is modifying my variable? testing?
13. 13 Problems with Java • Immutability not well implemented ◦ Variables can be modified easily ◦ “Race condition” → who is modifying my variable? testing? ◦ We can define everything “final”, but it’s hard to use.
14. 14 Problems with Java • Immutability not well implemented ◦ Variables can be modified easily ◦ “Race condition” → who is modifying my variable? testing? ◦ We can define everything “final”, but it’s hard to use. ◦ Java framework and libraries use to be mutable. (i.e: Collections and Collections Utils)
15. 15 Problems with Java • First class citizen functions
16. 16 Problems with Java • First class citizen functions ◦ Feature supported by Java 8, but in Java 7 there is no support for lambdas and functions as parameters or as a return type
17. 17 Problems with Java • First class citizen functions ◦ Feature supported by Java 8, but in Java 7 there is no support for lambdas and functions as parameters or as a return type ◦ Functional programming ◦ Listeners ◦ Callbacks
18. 18 Problems with Java • First class citizen functions ◦ Feature supported by Java 8, but in Java 7 there is no support for lambdas and functions as parameters or as a return type ◦ Functional programming ◦ Listeners ◦ Callbacks
19. 19 Problems with Java • First class citizen functions ◦ Feature supported by Java 8, but in Java 7 there is no support for lambdas and functions as parameters or as a return type ◦ Functional programming ◦ Listeners ◦ Callbacks
20. 20 Problems with Java • Data classes?
21. 21 Problems with Java • Data classes?
22. 22 Problems with Java • Data classes?
23. 23 Problems with Java • It’s complex to implement a safe singleton
24. 24 Problems with Java • It’s complex to implement a safe singleton • Object means, class with an unique implementation → Singleton
25. 25 Problems with Java • Is Java obsolete?
26. 26 Problems with Java • Is Java obsolete? ◦ Lambdas ◦ Functional programming ◦ Sealed classes
27. 27 Problems with Java • Is Java obsolete? ◦ Lambdas ◦ Functional programming ◦ Sealed classes • With Kotlin, can be used without third libraries and even using Java 6’s VM
28. 28 Problems with Java • Is Java obsolete? ◦ Lambdas ◦ Functional programming ◦ Sealed classes • With Kotlin, can be used without third libraries and even using Java 6’s VM • 100% interoperable with Java
29. 29 Problems with Java • Is Java obsolete? ◦ Lambdas ◦ Functional programming ◦ Sealed classes • With Kotlin, can be used without third libraries and even using Java 6’s VM • 100% interoperable with Java • Supported by Google for Android
30. Let’s use Kotlin!
31. 31 Using Kotlin • Android Studio
32. 32 Using Kotlin • Android Studio • Plugin Kotlin ◦ Projects from scratch ◦ Java projects with some Kotlin
33. 33 Using Kotlin • Android Studio • Plugin Kotlin ◦ Projects from scratch ◦ Java projects with some Kotlin • Lambda expressions
34. 34 Using Kotlin • Android Studio • Plugin Kotlin ◦ Projects from scratch ◦ Java projects with some Kotlin • Lambda expressions • Inline functions (A new object is not created, the code is replaced at runtime)
35. 35 Using Kotlin • Android Studio • Plugin Kotlin ◦ Projects from scratch ◦ Java projects with some Kotlin • Lambda expressions • Inline functions (A new object is not created, the code is replaced at runtime) • Null safety
36. 36 Using Kotlin • Android Studio • Plugin Kotlin ◦ Projects from scratch ◦ Java projects with some Kotlin • Lambda expressions • Inline functions (A new object is not created, the code is replaced at runtime) • Null safety • Smart cast
37. 37 Using Kotlin • Android Studio • Plugin Kotlin ◦ Projects from scratch ◦ Java projects with some Kotlin • Lambda expressions • Inline functions (A new object is not created, the code is replaced at runtime) • Null safety • Smart cast • String templates
38. 38 Using Kotlin • Android Studio • Plugin Kotlin ◦ Projects from scratch ◦ Java projects with some Kotlin • Lambda expressions • Inline functions (A new object is not created, the code is replaced at runtime) • Null safety • Smart cast • String templates • Primary constructors
39. 39 Using Kotlin • Interfaces with code
40. 40 Using Kotlin • Interfaces with code • Needless: ◦ Semicolon ◦ “new” ◦ Types definitions
41. 41 Kotlin Updates • Google IO 2017 → Google Supports Kotlin for Android Dev REFERENCES: • Android Developers: https://developer.android.com/kotlin/resources.html • Kotlin Online https://try.kotlinlang.org • Code Labs Google: https://codelabs.developers.google.com/?cat=Android
42. 42 Kotlin project in Android from scratch
43. 43 Kotlin project in Android step by step
44. 44 Kotlin project in Android step by step • Create project in the usual way
45. 45 Kotlin project in Android step by step • Create project in the usual way • Browse the plugins (Jetbrains) and install Kotlin plugin
46. 46 Kotlin project in Android step by step • Create project in the usual way • Browse the plugins (Jetbrains) and install Kotlin plugin • Restart the IDE
47. 47 Kotlin project in Android step by step • Create project in the usual way • Browse the plugins (Jetbrains) and install Kotlin plugin • Restart the IDE • Open the MainActivity ◦ Code - Convert Java File to Kotlin File ◦ Magic!
48. 48 Kotlin project in Android step by step • Create project in the usual way • Browse the plugins (Jetbrains) and install Kotlin plugin • Restart the IDE • Open the MainActivity ◦ Code - Convert Java File to Kotlin File ◦ Magic! • Tools → Kotlin → Configure Kotlin in project → Version ◦ Project full modified (including build.gradle - both, app and project)
49. 49 Kotlin project in Android step by step • Create project in the usual way • Browse the plugins (Jetbrains) and install Kotlin plugin • Restart the IDE • Open the MainActivity ◦ Code - Convert Java File to Kotlin File ◦ Magic! • Tools → Kotlin → Configure Kotlin in project → Version ◦ Project full modified (including build.gradle - both, app and project) • App build.gradle (add android extension sub-plugin): to access easily view’s elements from Activity ◦ apply plugin: ‘kotlin-android-extension’
50. 50 A Kotlin Activity • No public reserved word, in Kotlin everything is public • Inheritance • Override as a reserved word rather than an annotation • In function: first name, then the type • Null safety with “?”
51. 51 Activity and On-Click listener in Kotlin * Taken from https://developer.android.com/kotlin/get-started.html
52. 52 Item click listener in Kotlin * Taken from https://developer.android.com/kotlin/get-started.html
53. 53 A Kotlin Example • https://github.com/cdmunoz/KotlinTrainingApp
54. 54 Questions?