Snackbar와 SnackbarHostState

A Snackbar is a brief message that slides up at the bottom, like Message sent, then fades on its own. It informs without blocking the screen. 💬

A dialog demands a response; a Snackbar does not. Reach for it for quick confirmations, not for choices the user must make.

Showing a snackbar is driven by SnackbarHostState. This object holds the queue and gives you the function that triggers a message.

Wrap the state in remember so the same SnackbarHostState survives recomposition. A fresh one each frame would lose any pending message.

Tell Scaffold where snackbars appear by filling its snackbarHost slot with a SnackbarHost bound to your state.

The showSnackbar function suspends, because it waits while the message is visible. So you must call it from a coroutine, not directly in a click.

Grab a rememberCoroutineScope and launch showSnackbar inside it. That bridges a normal onClick to the suspend call safely.

Pass an actionLabel to add a button, such as Undo. The call returns a result telling you whether the user tapped that action.

Check the returned SnackbarResult. If it equals ActionPerformed, run your undo logic; otherwise the snackbar simply dismissed.

Set how long it lingers with SnackbarDuration: Short, Long, or Indefinite. Use Indefinite only when the message truly needs the user to act.

A single SnackbarHostState queues messages, showing them one at a time. So share one host per Scaffold rather than creating several.

Why must you launch showSnackbar inside a coroutine scope?

Remember a SnackbarHostState, wire it into Scaffold's snackbarHost, then launch showSnackbar from a scope. You can finish a polished app shell now. 🎉