animated_rotation_button_state.dart

class _AnimatedRotationButtonState
    extends AnimatedWidgetBaseState<AnimatedRotationButton> {
  Tween<double> _angleTween;

  @override
  void forEachTween(visitor) {
    _angleTween = visitor(
      _angleTween,
      widget.angle,
      (value) => Tween<double>(begin: value),
    );
  }

  @override
  Widget build(BuildContext context) {
    return Transform.rotate(
      angle: _angleTween.evaluate(animation,
      child: RaisedButton(
        color: Colors.blue,
        child: widget.child,
        onPressed: widget.onPressed,
      ),
    );
  }
}