This document summarizes a presentation about Kotlin features for Android development. It discusses Kotlin's concise syntax, null safety, lambdas, extension functions, and higher-order functions. It also covers Kotlin collections, coroutines, Anko for layouts and SQLite, and migrating existing Android projects to Kotlin. The presentation provides code examples for many of these features and recommends additional Kotlin learning resources.

1. Fall in love with Kotlin
#Kotlin #Android
Hari Vignesh Jayapalan
Android | UX Engineer

2. Now Official for Android
#Kotlin #Android

3. Kotlin is a statically typed
programming language for the JVM,
Android and the browser.
#Kotlin #Android

4. Session : Today
● Kotlin Features
● Advanced Core Features
● Anko for Android
● Migrating to Kotlin
● Drawbacks of Kotlin
#Kotlin #Android

5. Kotlin Features
#Kotlin #Android

6. #Kotlin #Android
#1 Concise
Reduced Boilerplate Code

7. Example : Concise
public class Event { //Java
private long id;
private String name;
private String url;
public long getId() {...}
public String getName() {...}
public String getUrl() {...}
public void setId(long id) {...}
public void setName(String name) {...}
public void setUrl(String url) {...}
@override public String toString(){...}
}
//Kotlin
data class Event(
var id: Long,
var name: String,
var url: String)
#Kotlin #Android

8. #Kotlin #Android
#2 Safe
Avoid Null-Pointer Exceptions

9. Example : Safe
//Won’t Compile //Compiles
#Kotlin #Android
var notNullEvent: Event = null var event: Event? = null

10. Example : Safe
#Kotlin #Android
//Null validation Java
if (text != null) {
int length = text.length();
}
//Null validation kotlin
text?.let {
val length = text.length
}
//or simply
val length = text?.length

11. Example : Safe
#Kotlin #Android
//Elvis Operator
val name = event?.name ?: "empty”
// !! Operator
val l = b!!.length

12. #Kotlin #Android
#3 Lambdas
Functional Support

13. Example : Lambdas
//Java
view.setOnClickListener( new
View.OnClickListener() {
@Override
public void onClick(View v) {
System.out.println("Button Clicked");
}
});
//Kotlin
view.setOnClickListener {
println("Hello world!")
}
#Kotlin #Android

14. #Kotlin #Android
#4 Extension Functions
Add new functions to any Class

15. Example : Extension Functions
//Normal Kotlin Function
fun triple(): Int {
return this * 3
}
//Extension Kotlin Function
fun Int.triple(): Int {
return this * 3
}
//Using Extension Function
var result = 3.triple()
#Kotlin #Android

16. Example : Extension Functions
//Extension Function for Glide
fun ImageView.loadImage(url: String) {
Glide.with(context).load(url).into(this)
}
//Usage
imageView.loadImage(url)
#Kotlin #Android

17. #Kotlin #Android
#5 Higher Order Functions
Return functions & functions as parameters

18. Example : Higher Order Functions
//Takes body() as parameter and returns T
fun <T> lock(lock: Lock, body: () -> T): T {
lock.lock()
try {
return body()
}
finally {
lock.unlock()
}
}
#Kotlin #Android

19. Core Features
#Kotlin #Android

20. //Kotlin collections
val list = listOf(1, 2, 3, 4, 5, 6)
println(list.filter{it%2==0})
Example : Collections
//Java
int[] list={1,2,3,4,5,6};
ArrayList<Integer> list2=new ArrayList<>();
for(int it:list){
if(it%2==0){
list2.add(it);
}
}
#Kotlin #Android

21. Collections
#Kotlin #Android

22. Coroutines
#Kotlin #Android

23. //Coroutine
Threads vs Coroutines
//Threads
#Kotlin #Android
Stacks
Thread 2
Thread 3Thread 1
Thread 1
Coroutine
1
Coroutine
2
Coroutine
3

24. Coroutines
● Light-weight threads
● Stackless coroutine - No mapping on main thread
● No context switching on processor
● Multitasking and managed by user
#Kotlin #Android

25. Definition : Coroutines
One can think of a coroutine as a light-weight thread. Like threads,
coroutines can run in parallel, wait for each other and communicate.
The biggest difference is that coroutines are very cheap, almost free:
we can create thousands of them, and pay very little in terms of
performance. True threads, on the other hand, are expensive to start
and keep around. A thousand threads can be a serious challenge for a
modern machine.
- kotlinlang.org
#Kotlin #Android

26. Example : Launch
//Coroutine Launch
fun main(args: Array<String>) {
println("Kotlin Start")
launch(CommonPool) {
delay(2000)
println("Kotlin Inside")
}
println("Kotlin End")
}
// The output will be
// Kotlin Start
// Kotlin End
// Kotlin Inside
#Kotlin #Android

27. Example : Async
// Parallel execution
private fun doWorksInParallel() {
val one = async(CommonPool) {
doWorkFor1Seconds() }
val two = async(CommonPool) {
doWorkFor2Seconds()}
launch(CommonPool) {
val combined = one.await() + "_" + two.await()
println("Kotlin Combined : " + combined)
}
}
suspend fun doWorkFor1Seconds(): String {
delay(1000)
return “doWorkFor1Seconds” }
suspend fun doWorkFor2Seconds(): String {
delay(2000)
return “doWorkFor2Seconds” }
#Kotlin #Android
// The output is
// Kotlin Combined :
//doWorkFor1Seconds_doWorkFor2Seconds

28. Anko for Android
#Kotlin #Android

29. Anko
● Commons: a lightweight library full of helpers for intents, dialogs, logging etc.
● Layouts: a fast and type-safe way to write dynamic Android layouts
● SQLite: a query DSL and parser collection for Android SQLite
● Coroutines: utilities based on the kotlinx.coroutines library
#Kotlin #Android

30. Anko Commons
● Intents
● Dialogs and toasts
● Logging
● Resources and dimensions
#Kotlin #Android

31. Example : Commons
//Calling Intent using Kotlin
val intent = Intent(this,
SomeOtherActivity::class.java)
intent.putExtra("id", 5)
intent.setFlag(Intent.FLAG_ACTIVITY_SINGLE_
TOP)
startActivity(intent)
//Calling Intent using Anko Commons
startActivity(intentFor<SomeOtherActivity>("id"
to 5).singleTop())
//Calling Intent using Anko Commons
startActivity(intentFor<SomeOtherActivity>("id"
to 5,"name" to "Hari"))
#Kotlin #Android

32. Example : Layouts
//using Anko to create layouts
verticalLayout {
val name = editText()
button("Say Hello") {
onClick { toast("Hello, ${name.text}!") }
}
}
//Output
#Kotlin #Android

33. Example : SQLite
//using Anko to create table
database.use {
createTable("User", true,
"id" to INTEGER + PRIMARY_KEY,
"name" to TEXT,
"photo" to BLOB)
}
//using Anko to query
db.select("User", "name")
.whereArgs("(_id > {userId}) and (name =
{userName})",
"userName" to "John",
"userId" to 42)
#Kotlin #Android

34. Example : Coroutines
//using Anko to create async task
fun authorizeUser(username: String, password: String) {
doAsync {
val authorized = signInBL.checkUserCredentials(
AuthCredentials(username = username, password = password))
activityUiThread {
if (authorized) {
toast("Signed!!!")
} else {
view.showAccessDeniedAlertDialog()
}
}
}
#Kotlin #Android

35. Lot More
#Kotlin #Android

36. Migrating to Kotlin
#Kotlin #Android

37. Drawbacks of Kotlin
#Kotlin #Android

38. Other Resources
● Mindorks - http://blog.mindorks.com/
● Kotlin Official - https://kotlinlang.org
● Kotlin for Android Developers - https://antonioleiva.com
● Kotlin Weekly - http://www.kotlinweekly.net
● PacktPub - https://www.packtpub.com/books/content/what-kotlin
● Kotlin Koans - https://kotlinlang.org/docs/tutorials/koans.html
#Kotlin #Android

39. #Kotlin #Android
Let’s stay in touch
Google “Hari Vignesh Jayapalan”
Thank you!

40. Content Credits
● Mindorks - http://blog.mindorks.com/
● Kotlin Official - https://kotlinlang.org
● Word Cloud - https://worditout.com/
● Kotlin for Android Developers - https://antonioleiva.com
#Kotlin #Android