kotlin coroutines code example

Example 1: coroutines kotlin android dependency

dependencies {
    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.7'
}

Example 2: kotlin coroutine scope

CoroutineScope
To start coroutine scope you can:
Use GlobalScope that has empty coroutine context.
Implement CoroutineScope interface.
Create a scope from a context:
with(CoroutineScope(context = context)) { ... }

Example 3: coroutines dependency

implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.9'

Example 4: kotlin coroutines

import kotlinx.coroutines.*
// Asynchronous execution
fun main() {
  GlobalScope.launch { 	// creates a new coroutine and continues
    doWorld()			// suspending function
  }
  println("World !") 	// execution continues even while coroutine waits
  runBlocking { 		// block main thread for 4 s (waits for 1rst coroutine)
  	delay(4000L) 		
  }
}
suspend fun doWorld() {
  delay(2000L) 		// non-blocking delay for 2000 milliseconds
  println("Hello")	// printed after "World !"
}

Example 5: kotlin coroutine builders

launch - Launches new coroutine without blocking
current thread and returns a reference to the coroutine
as a Job.
runBlocking - Runs new coroutine and blocks current
thread interruptible until its completion.
async - Creates new coroutine and returns its future
result as an implementation of Deferred.
withContext - Change a coroutine context for some
block.

Example 6: kotlin coroutine channel

Channels
fun CoroutineScope.produceSquares():
 ReceiveChannel<Int> = produce {
 for (x in 1..5) send(x * x)
 }
val squares = produceSquares()
repeat(5) { println(squares.receive()) } // 1, 4, 9, 16, 25
val squares2 = produceSquares()
for(square in squares2) print(square) // 1, 4, 9, 16, 25