animated_transform.dart

class AnimatedTransform extends ImplicitlyAnimatedWidget {
  const AnimatedTransform({
    Key key,
    @required this.transform,
    this.alignment = Alignment.center,
    this.child,
    Curve curve = Curves.linear,
    @required Duration duration,
    VoidCallback onEnd,
  }) : assert(transform != null), assert(alignment != null),
       super(key: key, curve: curve, duration: duration, onEnd: onEnd);

  final Matrix4 transform;
  final AlignmentGeometry alignment;
  final Widget child;

  @override
  _AnimatedTransformState createState() => _AnimatedTransformState();

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    super.debugFillProperties(properties);
    properties.add(DiagnosticsProperty<Matrix4>('transform', transform));
    properties.add(DiagnosticsProperty<AlignmentGeometry>('alignment', alignment));
  }
}

class _AnimatedTransformState extends AnimatedWidgetBaseState<AnimatedTransform> {
  AlignmentGeometryTween _alignment;
  Matrix4Tween _transform;

  @override
  void forEachTween(TweenVisitor<dynamic> visitor) {
    _transform = visitor(_transform, widget.transform, (dynamic value) => Matrix4Tween(begin: value as Matrix4)) as Matrix4Tween;
    _alignment = visitor(_alignment, widget.alignment, (dynamic value) => AlignmentGeometryTween(begin: value as AlignmentGeometry)) as AlignmentGeometryTween;
  }

  @override
  Widget build(BuildContext context) {
    return Transform(
      transform: _transform.evaluate(animation),
      alignment: _alignment.evaluate(animation),
      child: widget.child,
    );
  }

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder description) {
    super.debugFillProperties(description);
    description.add(DiagnosticsProperty<Matrix4Tween>('transform', _transform, defaultValue: null));
    description.add(DiagnosticsProperty<AlignmentGeometryTween>('alignment', _alignment, defaultValue: null));
  }
}