I had seen Jim once say about this ```val activity = LocalContext.current as Activity``` But I never...

# compose

[Rafiul Islam]

I had seen Jim once say about this

val activity = LocalContext.current as Activity

But I never found the answer.

[Adam Powell]

If you're writing platform dependent code that needs an activity you can't exactly just not use it, and laundering platform specific usage through other abstractions is sometimes useful, sometimes YAGNI.

[Adam Powell]

But it's worth noting that often the LocalContext is not an Activity, but instead it can be a chain of `ContextWrapper`s where the .baseContext leads to an Activity eventually

[Adam Powell]

this can often happen if a ContextThemeWrapper has been used to change the theme mid-view hierarchy. If you use the android:theme attribute in layout xml, one of these is created for you. If a ComposeView is placed as a child of such a subtree, LocalContext will be one of these wrappers.

[Adam Powell]

That said, depending on what you're doing with the activity you might find it more useful to pass a () -> Unit callback or similar to your composable and provide a lambda that makes the actual activity call. This can often aid in testability

[Adam Powell]

https://cs.android.com/androidx/platform/frameworks/support/+/androidx-main:activity[…]n/java/androidx/activity/compose/ActivityComposeUtils.kt;l=22 shows the unwrapping ContextWrappers approach and is used by the activity result API in the androidx.activity library

[Rafiul Islam]

Actually, I have been using a onFinish: () -> Unit callback for my code to finish the activity from composable functions for a while.

[Rafiul Islam]

I am a little bit confused just if you make it clear. So LocalContext will eventually get the activity, it might go through multiple loops. But it will return the activity right? Or is there any possibility it won't return the activity?

[Adam Powell]

If there is no activity to return then it won't return one. It's entirely possible to create a ContextThemeWrapper around a Service context, getSystemService to get the WindowManager, and add a ComposeView to it as a top-level window with the right lifecycle dependencies configured. At that point you have no activity, but you have a perfectly functional compose ui

[Adam Powell]

Android Auto projected mode operates more or less this way as well

[Rafiul Islam]

Yep, I got it. Thanks @Adam.