Unresolved reference: launch

Question

Trying to run some examples for Kotlin coroutines, but can\'t build my project. I\'m using the latest gradle release - 4.1

Any suggestions what to check/fix?

Her

Answer 1

If you are using Coroutines 1.0+, the import is no longer

import kotlinx.coroutines.experimental.*

but

import kotlinx.coroutines.launch

You would need the following in the dependencies closure of your build.gradle (for Coroutines 1.0.1):

implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.0.1'
implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.0.1"

Answer 2

Try this way,

//add this lines to gradle

 implementation "org.jetbrains.kotlinx:kotlinx-coroutines-core:$rootProject.kotlinx_coroutines"
 implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:$rootProject.kotlinx_coroutines"


  class xyz{
     private val job = Job()
        private val coroutinesScope: CoroutineScope = CoroutineScope(job + Dispatchers.IO)

      ....
     . ...
       coroutinesScope.launch {
                       // task to do
                        Timber.d("Delete Firebase Instance ID")
                    }


    // clear the job
      job.cancel()

    }

Answer 3

Launch isn't used anymore directly. The Kotlin documentation suggests using:

fun main() { 
    GlobalScope.launch { // launch a new coroutine in background and continue
        delay(1000L)
        println("World!")
    }
    println("Hello,") // main thread continues here immediately
    runBlocking {     // but this expression blocks the main thread
        delay(2000L)  // ... while we delay for 2 seconds to keep JVM alive
    } 
}

Answer 4

Like already answered in the comments, the import is missing for the kotlinx.coroutines.experimental.* package. You can have a look at my examples at GitHub if you like.

import kotlinx.coroutines.experimental.*

fun main(args: Array<String>) {

    launch(CommonPool) {
        delay(1000)
        LOG.debug("Hello from coroutine")
    }

}