Listen to changes in android Lifecycle in Composable and set and clear secure flag in onStart / onStop.

SecureScreen.kt

import android.app.Activity
import android.content.Context
import android.content.ContextWrapper
import android.view.WindowManager.LayoutParams.FLAG_SECURE
import androidx.compose.foundation.background
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.fillMaxSize
import androidx.compose.material3.Text
import androidx.compose.runtime.Composable
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.platform.LocalContext
import androidx.lifecycle.Lifecycle
import androidx.lifecycle.lifecycleScope
import kotlinx.coroutines.delay
import kotlinx.coroutines.launch
import java.lang.IllegalStateException

@Composable
fun SecureScreen() {
    val context: Context = LocalContext.current
    val activity = context.findActivity()

    SecureScreenContent(modifier = Modifier.fillMaxSize())

    ComposableLifecycleListener { source, event ->
        when (event) {
            Lifecycle.Event.ON_START -> activity.window.setFlags(FLAG_SECURE, FLAG_SECURE)
            Lifecycle.Event.ON_STOP -> {
                source.lifecycleScope.launch {
                    /*
                    Add a small delay to ensure we have navigated away from the secure screen.
                    Otherwise, it will still be visible during screen recording.
                     */
                    delay(200)
                    activity.window.clearFlags(FLAG_SECURE)
                }
            }
            else -> Unit
        }
    }
}

@Composable
private fun SecureScreenContent(modifier: Modifier) {
    Box(
        modifier = modifier.background(color = Color.Red),
        contentAlignment = Alignment.Center
    ) {
        Text(text = "Secure Screen")
    }
}

fun Context.findActivity(): Activity {
    var context = this
    while (context is ContextWrapper) {
        if (context is Activity) return context
        context = context.baseContext
    }
    throw IllegalStateException("Activity not found")
}