build method

@override Widget build(BuildContext context, Animation<double> primaryAnimation, Animation<double> secondaryAnimation, Widget child,)

Implementation

@override
Widget build(BuildContext context, Animation<double> primaryAnimation,
    Animation<double> secondaryAnimation, Widget child) {
  var exitAnimation = secondaryAnimation as ProxyAnimation;

  if (!exitAnimation.isDismissed) {
    var animation = CurvedAnimation(parent: secondaryAnimation, curve: curve);

    return Container(
        color: backgroundColor,
        child: Opacity(
          opacity: 1 - animation.value,
          child: Transform(
            alignment: Alignment.center,
            transform: Matrix4.identity()
              ..scale(1.0 - (1.0 - scale) * animation.value),
            child: child,
          ),
        ));
  } else {
    var animation = CurvedAnimation(parent: primaryAnimation, curve: curve);

    final double width = MediaQuery.of(context).size.width;
    // enter
    return Transform(
      transform: Matrix4.identity()
        ..translate(width * (1.0 - animation.value)),
      child: child,
    );
  }
}