flutter navigate to new page without ROUTE code example

Example 1: Flutter Navigator to new page

// Within the `FirstRoute` widget
onPressed: () {
  Navigator.push(
    context,
    MaterialPageRoute(builder: (context) => SecondRoute()),
  );
}

Example 2: im going from first screen to second and from there to third but dont want to go back in flutter

Navigator.pushAndRemoveUntil(
  context,
  MaterialPageRoute(builder: (context) => MainPage()),
  (Route<dynamic> route) => false,
);