Level 8

Side Effects

LaunchedEffect & Side Effects

Running code that isn't UI (timers, analytics, snackbars) inside Composable functions safely.

📚 Explanation

`LaunchedEffect` runs side effects (like API calls, timers) when a Composable enters composition or when keys change. `rememberCoroutineScope` provides a coroutine scope tied to the composition lifecycle for launching coroutines from callbacks.

Note: Code execution is not available for Android/Kotlin in the browser. Use Android Studio to run and test the app.

kotlin

@Composable
fun AutoSaveScreen(onSave: () -> Unit) {
    // launchedEffect runs ONCE when the component enters the screen
    // or when 'key1' changes.
    LaunchedEffect(Unit) {
        delay(5000) // Wait 5 seconds
        onSave()
    }

    // rememberCoroutineScope allows launching coroutines from callbacks (like onClick)
    val scope = rememberCoroutineScope()
    val snackbarHostState = remember { SnackbarHostState() }

    Button(onClick = {
        scope.launch {
            snackbarHostState.showSnackbar("Saved!")
        }
    }) {
        Text("Manual Save")
    }
}

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