kotlinx.coroutines

Library support for Kotlin coroutines with multiplatform support. This is a companion version for Kotlin 1.2.70 release.

NOTE: This is the latest experimental release. See COMPATIBILITY.md for details on migration.

GlobalScope.launch {
    delay(1000)
    println("Hello from Kotlin Coroutines!")
}

Modules

• common — common coroutines across all backends:
  • launch and async coroutine builders;
  • Job and Deferred light-weight future with cancellation support; * Dispatchers.Main for UI dispatcher for Android, Swing and JavaFx;
  • delay and yield top-level suspending functions;
  • Channel and Mutex communication and synchronization primitives;
  • produce and actor coroutine builders;
  • coroutineScope and supervisorScope scope builders;
  • SupervisorJob for supervision of coroutines hierarchies;
  • select expression support and more.
• core — Kotlin/JVM implementation of common coroutines with additional features:
  • Dispatchers.IO dispatcher for blocking coroutines.
• js — Kotlin/JS implementation of common coroutines with Promise support.
• native — Kotlin/Native implementation of common coroutines with runBlocking single-threaded event loop.
• reactive — modules that provide builders and iteration support for various reactive streams libraries:
  • Reactive Streams, RxJava 1.x and 2.x and Project Reactor.
• 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 CompletableFuture, Guava ListenableFuture, and synchronous networking/IO.

Documentation

• Presentations and videos:
  • Introduction to Coroutines (Roman Elizarov at KotlinConf 2017, slides)
  • Deep dive into Coroutines (Roman Elizarov at KotlinConf 2017, slides)
• Guides and manuals:
  • Guide to kotlinx.coroutines by example (read it first)
  • Guide to UI programming with coroutines
  • Guide to reactive streams with coroutines
• Change log for kotlinx.coroutines
• Coroutines design document (KEEP)
• Full kotlinx.coroutines API reference

Using in your projects

Note that these libraries are experimental and are subject to change.

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>0.30.1</version>
</dependency>

And make sure that you use the latest Kotlin version:

<properties>
    <kotlin.version>1.2.70</kotlin.version>
</properties>

Gradle

Add dependencies (you can also add other modules that you need):

implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:0.30.1'

And make sure that you use the latest Kotlin version:

buildscript {
    ext.kotlin_version = '1.2.70'
}

Make sure that you have either jcenter() or mavenCentral() in the list of repositories:

repository {
    jcenter()
}

Multiplatform

Core modules of kotlinx.coroutines are also available for Kotlin/JS and Kotlin/Native. If you write a common code that should get compiled or different platforms, add org.jetbrains.kotlinx:kotlinx-coroutines-core-common:<version> to your common code dependencies.

Android

Add kotlinx-coroutines-android module as dependency when using kotlinx.coroutines on Android:

implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:0.30.1'

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.

ProGuard

In obfuscated code, fields with different types can have the same names, and AtomicReferenceFieldUpdater may be unable to find the correct ones. To avoid field overloading by type during obfuscation, add this to your config:

-keepclassmembernames class kotlinx.** {
    volatile <fields>;
}

Building

This library is built with Gradle. To build it, use ./gradlew build. You can import this project into IDEA, but you have to delegate build actions to Gradle (in Preferences -> Build, Execution, Deployment -> Build Tools -> Gradle -> Runner)

Requirements

• JDK >= 1.8 referred to by the JAVA_HOME environment variable.
• JDK 1.6 referred to by the JDK_16 environment variable.

Contributions and releases

All development (both new features and bug fixes) is performed in develop branch. This way master sources always contain sources of the most recently released version. Please send PRs with bug fixes to develop branch. Fixes to documentation in markdown files are an exception to this rule. They are updated directly in master.

The develop branch is pushed to master during release.

• Full release procedure checklist is here.
• Steps for contributing new integration modules are explained here.