How Does Cancellation Work?
Learn how cancellation works.
We'll cover the following...
When a job is canceled, it changes its state to “Canceling.” Then, at the first suspension point, a CancellationException is thrown. We can catch this exception using a try-catch, but it’s recommended to rethrow it.
package kotlinx.coroutines.app
import kotlinx.coroutines.*
suspend fun main(): Unit = coroutineScope {
val job = Job()
launch(job) {
try {
repeat(1_000) { i ->
delay(200)
println("Printing $i")
}
} catch (e: CancellationException) {
println(e)
throw e
}
}
delay(1100)
job.cancelAndJoin()
println("Canceled successfully")
delay(1000)
}Catching exception using try-catch
Remember that a canceled coroutine is not just stopped—it’s canceled internally using an exception. Therefore, we can freely clean up everything inside the finally block. For instance, we can use a finally block to close a file or a database connection. Since most resource-closing mechanisms rely on the finally block (for example, if we read a file using useLines), we don’t need to ...