Toasts
Toasts are Banners that are dismissable and transient to the View. They may contain an action button.
Guidelines
Use a toast for messages in the context of a View in an app. Typical usage is for giving feedback to a user action. For example, after doing a destructive action, a toast showing an undo sentence and button.
Toasts are transient so they're best suited for informing the user of events, as opposed to ongoing states. For the latter, use Banners.
Toasts are only useful while the app is being focused. For messaging the user while the app is unfocused, consider using a Notification.
Each Toast should have a clear, simple and concise title.
Toasts should only include a button when necessary.
Toast titles should use Informal Heading style.