SnackBar({Key key, Widget content, Color backgroundColor, SnackBarAction action, Duration duration: _kSnackBarDisplayDuration, Animation<double> animation })

Creates a snack bar.

The content argument must be non-null.

Source 

SnackBar({
  Key key,
  this.content,
  this.backgroundColor,
  this.action,
  this.duration: _kSnackBarDisplayDuration,
  this.animation
}) : super(key: key) {
  assert(content != null);
}