"type 'double' is not a subtype of type 'int' in type cast" error in flutter. What should i do?

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I am doing a simple Curves Animation in flutter, but i am always getting an error like this "type 'double' is not a subtype of type 'int' in type cast" , what error i have made here?

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage>
    with SingleTickerProviderStateMixin {
  Animation animation;
  AnimationController animationController;
  @override
  void initState() {
    super.initState();
    animationController =
        AnimationController(duration: Duration(seconds: 3), vsync: this);
    animation = Tween(begin: -1, end: 0).animate(CurvedAnimation(
        curve: Curves.fastOutSlowIn, parent: animationController));
  }
  @override
  Widget build(BuildContext context) {
    final double width = MediaQuery.of(context).size.width;
    animationController.forward();
    return AnimatedBuilder(
        animation: animationController,
        builder: (BuildContext context, Widget child) {
          return Scaffold(
            body: Transform(
              transform:
                  Matrix4.translationValues(animation.value * width, 0, 0),
              child: Center(
                child: Text(
                  "Welcome",
                  style: TextStyle(fontWeight: FontWeight.bold, fontSize: 50),
                ),
              ),
            ),
          );
        });
  }
}