Show only one snackbar on screen at a time.
Snackbars appear above most elements on screen, and they are equal in elevation to the floating action button. However, they are lower in elevation than dialogs, bottom sheets, and navigation drawers.
Upon entrance, snackbars animate upwards from the bottom edge of the screen. When they appear, they do not block input.
They exit by being swiped off-screen or automatically disappear after a timeout or user interaction elsewhere (such as summoning a new surface or activity).