Is `await`ing in fragment A for a computation done in another fragment B possible in anyway? I know ...

# android

[manlan]

Is `await`ing in fragment A for a computation done in another fragment B possible in anyway?
I know this is a dumb question, but I'm finding it hard to chain a sequence of asynchronous operations.

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[Casey Brooks]

I’m not entirely sure what you’re trying to do with captureLocation and capturePhoto, but doing it within the “scope” of the fragment is generally considered bad practice. But using ViewModels as a shared layer between those fragments is perfectly fine. The ViewModel can make those async calls and dispatch the results to the fragments as-needed

[brandonmcansh]

Are you trying to emulate an activity result via a fragment?

[Ian Lake]

This isn't a good idea, particularly when you take into account config changes and process death/recreation while on some other fragment

[Ian Lake]

You absolutely can wrap the Fragment Result API up in a channel/Flow, but you'll need to be collecting that as part of a lifecycle method vs just as a suspending function
https://developer.android.com/training/basics/fragments/pass-data-between

[manlan]

@Casey Brooks I'm requesting location via fusedlocationproivider in captureLocation() and going to a new fragment that handles face capture in capturePhoto(). I need to somehow wait for these two things to happen and proceed accordingly.

[manlan]

@Ian Lake So I can do this properly only via a callback based approach, and not via coroutines. Correct?

[Ian Lake]

Your coroutine context will not reliability survive through to completion

[manlan]

Got it, thanks @Ian Lake 🙂

[manlan]

One thing though..I didn't get how to exactly pop off the current fragment (in my case, the selfie fragment) after I set the result 😐

[Ian Lake]

You didn't include how you added the selfie fragment, but you'd want to do the opposite of that 🙃

[manlan]

🙂 findNavController().navigate(FragmentADirections.actionToFragmentB())

Also, what if I'm using an earlier stable version? How do I do this?

[Ian Lake]

Ah, then you navController.popBackStack() and can use Navigation's returning a result API, which is stable: https://developer.android.com/guide/navigation/navigation-programmatic#returning_a_result

[manlan]

Thanks, but now the fragment is not popping off.

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[manlan]

It keeps reappearing 😞

[Ian Lake]

Sounds like you're calling navigate within a LiveData observe block that is retriggering every time you go back to your other Fragment. LiveData isn't made for events

[manlan]

It's cool you guessed it right even without looking at the code. That's indeed the problem!
So LiveData is only about updating UI based on changes in data?
And normal method calls or callbacks are the only option in a case like mine?

[Ian Lake]

You can certainly warp LiveData in unnatural ways to handle events ala https://link.medium.com/jfSrjj6i38

[Ian Lake]

But yes, using something built for event streams like regular callbacks or Flow is perhaps the cleaner solution - kind of like using the right tool for the job

[manlan]

Thanks for the pointer to the article. Exactly covered my case 😄
Can you if possible point me to some guide about achieving the same using Flow ?