Recompose screen on coming back from an activity

What you need to do is change a state in your composable when you receive the answer from the activity... something like this:

First, make your activity (I'm assuming you already have one) return the data as of it would return to another activity, using setResult method.

class ResponseActivity : AppCompatActivity() {

    // Call this function to return a String to the caller
    private fun sendActivityResult(text: String) {
        val anInt = intent.getIntExtra(EXTRA_INT, -1)
        setResult(RESULT_OK, Intent().apply {
            putExtra(EXTRA_STRING, "$text: $anInt")
        })
        finish()
    }

    companion object {
        const val EXTRA_INT = "anInt"
        const val EXTRA_STRING = "anString"
    }
}

The activity above receives an Int as input param and returns a String to the caller.

The second thing you need is declare an ActivityResultContract.

class MyActivityResultContract : ActivityResultContract<Int, String>() {
    override fun createIntent(context: Context, input: Int): Intent {
        return Intent(context, ResponseActivity::class.java).apply {
            putExtra(EXTRA_INT, input)
        }
    }

    override fun parseResult(resultCode: Int, intent: Intent?): String {
        return if (resultCode == Activity.RESULT_OK) {
            return intent?.getStringExtra(EXTRA_STRING) ?: "Empty result"
        } else {
            "Nothing selected"
        }
    }
}

Finally, you can call the ResponseActivity from your composable using rememberLauncherForActivityResult function like below:

@Composable
fun GetActivityResultScreen() {
    var textResult by rememberSaveable { mutableStateOf("") }
    val launcher = rememberLauncherForActivityResult(MyActivityResultContract()) { text ->
        textResult = text
    }

    Column {
        Button(onClick = {
            launcher.launch(Random.nextInt(0, 100))
        }) {
            Text("Launch Activity")
        }
        Text(textResult)
    }
}

You can find the full source in my repository: ResponseActivity class and GetActivityResult and MyActivityResultContract composable.