Cancelling a Coroutine

Call job.cancel() to stop a coroutine. Cancellation is delivered as a CancellationException thrown at the next suspension point (delay, yield, withContext, a channel call...).

import kotlinx.coroutines.*

fun main() = runBlocking {
    val job = launch {
        repeat(10) { i ->
            println("Syncing chunk $i")
            delay(100)
        }
    }
    delay(250)
    println("User pressed Cancel")
    job.cancelAndJoin()
    println("Sync stopped. Cancelled = ${job.isCancelled}")
}

Syncing chunk 0
Syncing chunk 1
Syncing chunk 2
User pressed Cancel
Sync stopped. Cancelled = true

• Screen closed: viewModelScope / lifecycleScope cancels automatically.
• User action: you keep the Job and call cancel() (e.g. a new search replaces the old one).
• Timeout: withTimeout cancels the block when time runs out.
• Failure: a failing sibling in coroutineScope.