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;
  final double width = MediaQuery.of(context).size.width;

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

    return Container(
        color: backgroundColor,
        child: Transform(
          alignment: Alignment.bottomRight,
          transform: Matrix4.identity()
            ..rotateZ(angle * animation.value)
            ..leftTranslate(width * animation.value),
          child: child,
        ));
  } else {
    var animation = CurvedAnimation(parent: primaryAnimation, curve: curve);

    return Transform(
      alignment: Alignment.bottomLeft,
      transform: Matrix4.identity()
        ..rotateZ(-angle * (1.0 - animation.value))
        ..leftTranslate(-width * (1.0 - animation.value)),
      child: child,
    );
  }
}