kotlinx.coroutines
Library support for Kotlin coroutines with multiplatform support.
This is a companion version for Kotlin 1.4.0
release.
suspend fun main() = coroutineScope {
launch {
delay(1000)
println("Kotlin Coroutines World!")
}
println("Hello")
}
Play with coroutines online here
Modules
- core — common coroutines across all platforms:
- launch and async coroutine builders returning Job and Deferred light-weight futures with cancellation support;
- Dispatchers object with Main dispatcher for Android/Swing/JavaFx, and Default dispatcher for background coroutines;
- delay and yield top-level suspending functions;
- Flow — cold asynchronous stream with flow builder and comprehensive operator set (filter, map, etc);
- Channel, Mutex, and Semaphore communication and synchronization primitives;
- coroutineScope, supervisorScope, withContext, and withTimeout scope builders;
- MainScope() for Android and UI applications;
- SupervisorJob() and CoroutineExceptionHandler for supervision of coroutines hierarchies;
- select expression support and more.
- core/jvm — additional core features available on Kotlin/JVM:
- Dispatchers.IO dispatcher for blocking coroutines;
- Executor.asCoroutineDispatcher extension, custom thread pools, and more.
- core/js — additional core features available on Kotlin/JS:
- Integration with
Promise
via Promise.await and promise builder; - Integration with
Window
via Window.asCoroutineDispatcher, etc.
- Integration with
- test — test utilities for coroutines:
- Dispatchers.setMain to override Dispatchers.Main in tests;
- TestCoroutineScope to test suspending functions and coroutines.
- debug — debug utilities for coroutines:
- DebugProbes API to probe, keep track of, print and dump active coroutines;
- CoroutinesTimeout test rule to automatically dump coroutines on test timeout.
- reactive — modules that provide builders and iteration support for various reactive streams libraries:
- Reactive Streams (Publisher.collect, Publisher.awaitSingle, kotlinx.coroutines.reactive.publish, etc),
- Flow (JDK 9) (the same interface as for Reactive Streams),
- RxJava 2.x (rxFlowable, rxSingle, etc), and
- RxJava 3.x (rxFlowable, rxSingle, etc), and
- Project Reactor (flux, mono, etc).
- ui — modules that provide coroutine dispatchers for various single-threaded UI libraries:
- Android, JavaFX, and Swing.
- integration — modules that provide integration with various asynchronous callback- and future-based libraries:
- JDK8 CompletionStage.await, Guava ListenableFuture.await, and Google Play Services Task.await;
- SLF4J MDC integration via MDCContext.
Documentation
- Presentations and videos:
- Introduction to Coroutines (Roman Elizarov at KotlinConf 2017, slides)
- Deep dive into Coroutines (Roman Elizarov at KotlinConf 2017, slides)
- Kotlin Coroutines in Practice (Roman Elizarov at KotlinConf 2018, slides)
- Guides and manuals:
- Compatibility policy and experimental annotations
- Change log for kotlinx.coroutines
- Coroutines design document (KEEP)
- Full kotlinx.coroutines API reference
Using in your projects
The libraries are published to kotlinx bintray repository, linked to JCenter and pushed to Maven Central.
Maven
Add dependencies (you can also add other modules that you need):
<dependency>
<groupId>org.jetbrains.kotlinx</groupId>
<artifactId>kotlinx-coroutines-core</artifactId>
<version>1.4.2</version>
</dependency>
And make sure that you use the latest Kotlin version:
<properties>
<kotlin.version>1.4.0</kotlin.version>
</properties>
Gradle
Add dependencies (you can also add other modules that you need):
dependencies {
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.4.2'
}
And make sure that you use the latest Kotlin version:
buildscript {
ext.kotlin_version = '1.4.0'
}
Make sure that you have either jcenter()
or mavenCentral()
in the list of repositories:
repository {
jcenter()
}
Gradle Kotlin DSL
Add dependencies (you can also add other modules that you need):
dependencies {
implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.4.2")
}
And make sure that you use the latest Kotlin version:
plugins {
kotlin("jvm") version "1.4.0"
}
Make sure that you have either jcenter()
or mavenCentral()
in the list of repositories.
Multiplatform
Core modules of kotlinx.coroutines
are also available for
Kotlin/JS and Kotlin/Native.
In common code that should get compiled for different platforms, you can add dependency to kotlinx-coroutines-core
right to the commonMain
source set:
commonMain {
dependencies {
implementation("org.jetbrains.kotlinx:kotlinx-coroutines-core:1.4.2")
}
}
Android
Add kotlinx-coroutines-android
module as dependency when using kotlinx.coroutines
on Android:
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.4.2'
This gives you access to Android Dispatchers.Main coroutine dispatcher and also makes sure that in case of crashed coroutine with unhandled exception this exception is logged before crashing Android application, similarly to the way uncaught exceptions in threads are handled by Android runtime.
R8 and ProGuard
R8 and ProGuard rules are bundled into the kotlinx-coroutines-android
module.
For more details see "Optimization" section for Android.
Avoiding including the debug infrastructure in the resulting APK
The kotlinx-coroutines-core
artifact contains a resource file that is not required for the coroutines to operate
normally and is only used by the debugger. To exclude it at no loss of functionality, add the following snippet to the
android
block in your gradle file for the application subproject:
packagingOptions {
exclude "DebugProbesKt.bin"
}
JS
Kotlin/JS version of kotlinx.coroutines
is published as
kotlinx-coroutines-core-js
(follow the link to get the dependency declaration snippet).
You can also use kotlinx-coroutines-core
package via NPM.
Native
Kotlin/Native version of kotlinx.coroutines
is published as
kotlinx-coroutines-core-native
(follow the link to get the dependency declaration snippet).
Only single-threaded code (JS-style) on Kotlin/Native is currently supported.
Kotlin/Native supports only Gradle version 4.10 and you need to enable Gradle metadata in your
settings.gradle
file:
enableFeaturePreview('GRADLE_METADATA')
Since Kotlin/Native does not generally provide binary compatibility between versions,
you should use the same version of Kotlin/Native compiler as was used to build kotlinx.coroutines
.