How to catch all the exceptions possibly thrown by multiple

Question

How to catch all the exceptions possibly thrown by multiple jobs launched in same scope SupevisorScope Currently I m doing something like this but no exceptions are getting caught

Erik · Answer

I think a coroutine exception handler only works if installed in the uppermost context Are you using the handler in a scope within the context of another

Kshitij Patil · Answer

You mean `GlobalScope` I read about that and also found all examples of exception handling shown either in `GlobalScope` or `runBlocking` block I also think the same but am looking for any other ways to handle my usecase

Erik · Answer

No I mean where you have a coroutine scope i e one that already has a context and exception handler but you try to switch context exception handler is a coroutine context in a coroutine inside that scope I think that s not possible you d have to create a scope and put your exception handler there

Kshitij Patil · Answer

The parent scope in my case is `lifecycleScope` of `Fragment` Idk if it has an exception handler but as you said I ve to create a scope and put exception Handler there is exactly what I ve done FYI I also tried to pass exceptionHandler to `launch` amp `async` but nothing worked

Erik · Answer

From this article <https medium com androiddevelopers exceptions in coroutines ce8da1ec060c> see the following code ```val handler = CoroutineExceptionHandler context exception gt println Caught $exception val scope = CoroutineScope Job scope launch handler launch throw Exception Failed coroutine ``` In the above code the exception will be handled by `handler` However the following code will not handle your exception in `handler` because the handler is not installed in the outer coroutine ```val scope = CoroutineScope Job scope launch launch handler throw Exception Failed coroutine ``` Quote from the article gt The inner launch will propagate the exception up to the parent as soon as it happens since the parent doesn t know anything about the handler the exception will be thrown

Erik · Answer

A few examples handler handles exception handler handles exception handler does not handle exception

Erik · Answer

<https pl kotl in cWBqHpTOr> handler in the scope instead of the outer coroutine

Erik · Answer

So in your fragment you should be able to `lifecycleScope launch handler Do exceptional stuff ` or just create your own `CoroutineScope handler ` but don t forget to cancel the scope on fragment destroy stop pause depending on when you create the scope and when stuff needs to cancel

Kshitij Patil · Answer

But what s wrong with the snippet that I shared Why it s not working As I said I ve tried to launch jobs using `scope launch handler ` But this doesn t work I ll share a playground link with the code that doesn t work

Kshitij Patil · Answer

Also I believe in playground we re much closer to `GlobalScope` whereas Fragment have `lifecycleScope` and I m trying to create custom scope out of it which I believe won t be able to handle exceptions I ll give a shot to `lifecycleScope launch handler ` as that seems promising but my purpose was to have a `supervisorScope` i e failing any child coroutine should not cause others to fail and neither cause any Runtime Exception I m launching independent network calls which might fail and I ve a code associated with it to reflect those errors on UI the problem is handling exceptions seperately for each job gives me the desired effect but I lose the ability to get to know whether all the jobs are successful so that I can show Success Toast Snackbar at the very end

Erik · Answer

You might be able to use `async ` for that do many calls in parallel and then `await ` all `Deferred lt T gt ` awaiting rethrows exceptions that happened in the block which you can simply `try` `catch` If anything you expect is caught you can show your UI notice

Kshitij Patil · Answer

Yes It works that way I was just concerned why it doesn t work with `exceptionHandler`