Answers for "what is a snackbar in flutter"

flutter snackbar

ScaffoldMessenger.of(context).showSnackBar(SnackBar(
                content: Text("Your Text"),
                duration: Duration(milliseconds: 300),
              ));

snackbar in flutter

final snackBar = SnackBar(content: Text('Yay! A SnackBar!'));

// Find the ScaffoldMessenger in the widget tree
// and use it to show a SnackBar.
ScaffoldMessenger.of(context).showSnackBar(snackBar);

snackbar in flutter

final snackBar = SnackBar(
  content: Text('Yay! A SnackBar!'),
  action: SnackBarAction(
    label: 'Undo',
    onPressed: () {
      // Some code to undo the change.
    },
  ),
);

Flutter snackbar top

RaisedButton(
  child: Text('Show Top Snackbar'),
  onPressed: () {
    Flushbar(
      flushbarPosition: FlushbarPosition.TOP,
    )
      ..title = "Hey Ninja"
      ..message = "Lorem Ipsum is simply dummy text of the printing and typesetting industry"
      ..duration = Duration(seconds: 3)
      ..show(context);
  },
),