问题
Using kotlinx.coroutines lib I can't catch an exception if it was thrown after coroutine is canceled. This leads to app crash.
fun foo() {
val job = launch(UI) {
try {
Log.d("TAG", "Start coroutine")
run(CommonPool) {
Log.d("TAG", "Start bg task")
// Intentionally make bg task running for a long time
SystemClock.sleep(2000)
Log.d("TAG", "Throw bg task exception")
throw RuntimeException("Bg task exception")
}
} catch (e: Exception) {
Log.e("TAG", "Handle coroutine exception", e)
}
}
launch(UI) {
delay(1000)
Log.d("TAG", "Cancel job = ${job.cancel()}")
}
}
Running this functions on Android produces the following log output
07-26 15:09:10.038 31518-31518/co.foo.bar D/MainActivity: Start coroutine
07-26 15:09:10.044 31518-31547/co.foo.bar D/MainActivity: Start bg task
07-26 15:09:11.046 31518-31518/co.foo.bar D/MainActivity: Cancel job = true
07-26 15:09:11.047 31518-31518/co.foo.bar E/MainActivity: Handled coroutine exception
java.util.concurrent.CancellationException: Job was cancelled
at kotlinx.coroutines.experimental.JobSupport$CompletedExceptionally.getException(Job.kt:921)
at kotlinx.coroutines.experimental.RunCompletion.afterCompletion(Builders.kt:198)
...
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
07-26 15:09:12.046 31518-31547/co.foo.bar D/MainActivity: Throwing bg task exception
--------- beginning of crash
07-26 15:09:12.046 31518-31547/co.foo.bar E/AndroidRuntime: FATAL EXCEPTION: ForkJoinPool.commonPool-worker-1
Process: co.foo.bar, PID: 31518
java.lang.RuntimeException: Bg task exception
at co.foo.barsample.MainActivity$onCreate$1$job$1$1.doResume(MainActivity.kt:36)
at kotlin.coroutines.experimental.jvm.internal.CoroutineImpl.resume(CoroutineImpl.kt:54)
at kotlinx.coroutines.experimental.DispatchTask.run(CoroutineDispatcher.kt:120)
at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1383)
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:256)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1123)
at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1961)
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1909)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:128)
07-26 15:09:12.050 1705-2190/system_process W/ActivityManager: Force finishing activity co.foo.bar/co.foo.barsample.MainActivity
Seems to be calling cancel()
throws CancellationException
which is caught successfully. But the subsequent RuntimeException
is not caught. I suppose the following exceptions after the job is canceled should be ignored by the lib? Or how I can cancel job silently without throwing a CancellationException
exception?
回答1:
Use CoroutineExceptionHandler as additinoal coroutine context to handle exceptions, for launch
or run
like
run(CommonPool + CoroutineExceptionHandler({ _, e ->
Log.e("TAG", "CoroutineExceptionHandler", e)
})) {
...
}
or
launch(UI + CoroutineExceptionHandler({ _, e ->
Log.e("TAG", "CoroutineExceptionHandler", e)
})) {
...
}
来源:https://stackoverflow.com/questions/45326818/cant-catch-exception-throwing-after-kotlin-coroutine-is-cancelled