Brief description into Kotlin Coroutines on GoNative Tech conference in Yerevan

1. KOTLIN
COROUTINES
in Android

2. 2018 / KOTLIN COROUTINES IN ANDROID
COROUTINES
Async
easy
Coroutines provide a way to
avoid blocking a thread and
simplify asynchronous
programming
SLIDE HEADLINE / Kotlin Coroutines in Android

3. COROUTINES
SLIDE HEADLINE / Kotlin Coroutines in Android
Blocking vs
Suspending
Coroutines are computations
that can be suspended without
blocking a thread
Suspending
2018 / KOTLIN COROUTINES IN ANDROID

4. COROUTINES
SLIDE HEADLINE / Kotlin Coroutines in Android
Launch
launch { … } is a Kotlin regular
function, which takes
suspending block and returns a
Job instance
Suspending
Launch
2018 / KOTLIN COROUTINES IN ANDROID

5. COROUTINES
SLIDE HEADLINE / Kotlin Coroutines in Android
Async
Await
async { … } in Kotlin is regular
function with suspending
parameter
await() is a method to get value
from suspending function done
asynchronous
Suspending
Launch
Async / await
2018 / KOTLIN COROUTINES IN ANDROID

6. Network
request
We want to send a request to
get some information …
fun getLocation(): Location {
/// gets current location
return location
}
2018 / KOTLIN COROUTINES IN ANDROID

7. Network
request
… and some more information
based on previous ...
fun getLocation(): Location { … }
fun getWeather(location: Location): Weather {
/// gets weather for current location
return weather
}
2018 / KOTLIN COROUTINES IN ANDROID

8. Network
request
… and show the result
fun getLocation(): Location { … }
fun getWeather(location: Location): Weather { … }
fun showWeather(weather: Weather) {
/// shows weather on the screen
}
2018 / KOTLIN COROUTINES IN ANDROID

9. fun getLocationAsync(cb: (Location) -> Unit) {
/// gets current location and returns it
/// with callback when done
}
Callbacks
We can do same with callbacks
2018 / KOTLIN COROUTINES IN ANDROID

10. fun getLocationAsync(cb: (Location) -> Unit) { … }
fun getWeatherAsync(location: Location,
cb: (Weather) -> Unit) {
/// gets weather for current location async
}
Callbacks
We can do same with callbacks
2018 / KOTLIN COROUTINES IN ANDROID

11. fun getLocationAsync(cb: (Location) -> Unit) { … }
fun getWeatherAsync(location: Location,
cb: (Weather) -> Unit) { … }
fun showWeather(weather: Weather) {
/// shows weather on the screen
}
Callbacks
We can do same with callbacks
2018 / KOTLIN COROUTINES IN ANDROID

12. fun getLocationAsync(cb: (Location) -> Unit) { … }
fun getWeatherAsync(location: Location,
cb: (Weather) -> Unit) { … }
fun showWeather(weather: Weather) { … }
fun processWeather() {
getLocationAsync { location ->
getWeatherAsync { weather ->
showWeather(weather)
}
}
}
Callbacks
We can do same with callbacks
2018 / KOTLIN COROUTINES IN ANDROID

13. Suspending
function
Suspending function suspends
the coroutine, without blocking
the thread
suspend fun getLocation(): Location {
/// gets current location & suspends
return location
}
2018 / KOTLIN COROUTINES IN ANDROID

14. Suspending
function
Suspending function suspends
the coroutine, without blocking
the thread
suspend fun getLocation(): Location { … }
suspend fun getWeather(location: Location): Weather {
/// gets weather for current location &
/// suspends
return weather
}
2018 / KOTLIN COROUTINES IN ANDROID

15. Suspending
function
Suspending function suspends
the coroutine, without blocking
the thread
2018 / KOTLIN COROUTINES IN ANDROID
suspend fun getLocation(): Location { … }
suspend fun getWeather(location: Location)
: Weather { … }
fun showWeather(weather: Weather) {
/// shows weather on the screen
}
suspend fun processWeather() {
val location = getLocation()
val weather = getWeather(location)
showWeather(weather)
}

16. 2018 / KOTLIN COROUTINES IN ANDROID

17. Launch
coroutine
/** Simple countdown with coroutines */
fun countdown(start: Int) {
launch(UI) {
for (i in start downTo 0) {
/// show time
delay(1000)
}
}
}
2018 / KOTLIN COROUTINES IN ANDROID

18. Place your screenshot
here
2018 / KOTLIN COROUTINES IN ANDROID

19. Thanks!
Any questions?
You can find me at
me@robertlevonyan.com
Or tweet
@robertlevonyan