Kotlin-ize your Android Development

Introduction to Kotlin for Android, it's features, issues and some amazing stuff.

Transcript

1. Kotlin-ize your Android Development
2. Akshay Chordiya +AkshayChordiya • Indie Android Developer • Graduated in 2016 Who am I?
3. • Why another language? • Problems with Java - Android • What’s Kotlin • Features • Issues • And finally… questions Agenda
4. Why another language?
5. “Java is old, too much verbose and don’t forget the infamous NullPointerException“
6. Problems with Java -- Android • Stuck at Java 6-7 • Restrictions to add functionality to Platform APIs • Android loves Inheritance • Lots of boilerplate • Ceremony of APIs • Android loves to throw nulls • Need of Modern coding style • And so much more….
7. What’s otlin?
8. “Kotlin is a new programming language targeting JVM, Android and even JavaScript.”
9. Kotlin • Modern & Statically typed • Targets JVM, Android and JavaScript • Works everywhere where Java works • 100% interoperable with Java™ • Combines Object Oriented and Functional features • Made by good folks at JetBrains • Open source
10. Big Players using Kotlin
11. Little bit about the Syntax
12. // String (Implicitly inferred) val spell = "Lumos" // Int val number = 74 // Explicit type var spells: List<String> = ArrayList() Variables // String (Implicitly inferred) val spell = "Lumos" // Int val number = 74 // Explicit type var spells: List<String> = new ArrayList()
13. “Use val for a value that won’t change” - Immutable val vs var “Use var for something that will vary with time.” - Mutable
14. fun add(a: Int, b: Int): Int { return a + b } Functions fun add(a: Int, b: Int) = a + b fun add(a: Int = 0, b: Int = 0) = a + b
15. Features
16. Null Safety
17. // Compile time error val spell: String = null // OK val spell: String? = null Declaring null variables
18. // Compile time error var spell: String = "Lumos" spell = null // OK var spell: String? = "Lumos" spell = null Even...
19. // Compile time error val spell: String? = null val length = spell.length // OK val spell: String? = null if (spell != null) { // Smart cast val length = spell.length } Null Safety
20. // Safe val spell: String? = null val length = spell?.length // Safe with else val length = spell?.length ?: -1 Kotlin-ized way
21. String interpolation
22. String interpolation fun sayHello(message: String) { println("Welcome $message") } fun sayTime() { println("Time: ${System.currentTimeMillis()}") }
23. Lambda Expressions
24. mButton.setOnClickListener { // Your logic } Lambda Expressions mButton.setOnClickListener { // Using the view parameter v -> v.visibility = GONE }
25. fun consume(f: () -> Unit): Boolean { f() return true } Higher Order Functions inline fun consume(f: () -> Unit): Boolean { f() return true }
26. Extension functions
27. fun View.visible() { visibility = VISIBLE } fun View.visible() { visibility = VISIBLE } fun String.isEmail(): Boolean { return Patterns.EMAIL_ADDRESS.matcher(this).matches() } fun String.isEmail(): Boolean { return Patterns.EMAIL_ADDRESS.matcher(this).matches() } Example: Extension functions
28. val email = "go.kotlin@android.com" if (email.isEmail()) { // Do login } Usage: Extension Function textView.visible()
29. inline fun SharedPreferences. edit(func: SharedPreferences.Editor.() -> Unit) { val editor = edit() editor.func() editor.apply() } inline fun SharedPreferences. edit(func: SharedPreferences.Editor.() -> Unit) { val editor = edit() editor.func() editor.apply() } Extension + Higher Order functions // Usage val pref = PreferenceManager.getDefaultSharedPreferences(context) pref.edit{ putString("first_name", "Akshay") putString("last_name", "Chordiya") remove("last_name") }
30. Smart Cast // Java way if (view instanceof TextView) { ((TextView) view).setText("Avifors"); } // Kotlin way if (view is TextView) { // Smart casting view.text = "Avifors" }
31. Ninja functions
32. let block textView?.let { textView.visible() }
33. apply block textView?.apply { visible() }
34. with function with(textView) { text = "Accio" visible() } val textView = with(TextView(this)) { text = "Accio" visible() this }
35. when expression override fun onOptionsItemSelected (item: MenuItem) = when (item.itemId) { R.id.action_about -> consume { startActivity(Intent( baseContext, AboutActivity:: class.java)) } else -> super.onOptionsItemSelected(item) }
36. Issues
37. Issues • Slightly increased build time • Adds Dex Count (6K) to your app • No static methods and variables. The same functionality can be achieved using companion objects • Difficulty in coding in functional paradigm
38. Conclusion
39. “With Kotlin our code base is shrinked down.”
40. “Plenty of app crashes are cut down”
41. ”Kotlin makes Android development a lot more fun again”
42. What’s next?
43. Questions?
44. References • All the images and logos used are trademarks of respective companies. • Kotlin Official Website • Why Kotlin-ize your Android Development Medium - Akshay Chordiya • Antonio Leiva Blog • Why You Should Start Using Kotlin to Supercharge Your Android Development in 2017 • Android Development with Kotlin — Jake Wharton • Kotlin - Android document by Square • Droidcon NYC 2016 - Kotlin in Production • Being more productive with Kotlin
45. Thank you #HappyCoding