sdd_anim_02.dart

const _kDuration = const Duration(milliseconds: 2000);
const _kAnimInterval03 = const Interval(.00, .90);
...
  Widget _buildAnimation(BuildContext context, Widget child) {
    return Container(
      child: Container(
        width: _kActionSize * 4,
        height: 256.0,
        color: Colors.black87,
        child: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.start,
            children: List.generate(_kCount, (i) {
              return SlideTransition(
                position: dxPositions[2 - i],
                child: _buildWidget(context, 2 - i),
              );
            }),
          ),
        ),
      ),
    );
  }