build method Null safety

Implementation

@override
Widget build(BuildContext context) {
  final AppLocalizations appLocalizations = AppLocalizations.of(context);
  final Size screenSize = MediaQuery.of(context).size;
  return Stack(
    children: <Widget>[
      Container(
        color: const Color.fromARGB(255, 225, 208, 208),
        height: screenSize.height,
      ),
      Column(
        children: <Widget>[
          Flexible(
            flex: 8,
            child: Stack(
              children: <Widget>[
                Positioned(
                  top: -screenSize.height / 8,
                  left: screenSize.width / 16,
                  child: Transform.rotate(
                    // We rotate the container with this angle in order to
                    // correctly align the rotation to the svg.
                    angle: -0.22828907, // 13.08 degrees
                    child: Container(
                      color: const Color.fromARGB(255, 3, 129, 65),
                      width: screenSize.width,
                      height: screenSize.height / 2,
                    ),
                  ),
                ),
                Positioned(
                  top: screenSize.height / 8,
                  left: screenSize.width / 8,
                  child: SvgPicture.asset(
                    'assets/onboarding/scan_example.svg',
                    width: screenSize.width / 2,
                    height: screenSize.height / 4,
                  ),
                ),
              ],
            ),
          ),
          Flexible(
            flex: 3,
            child: Padding(
              padding: EdgeInsets.only(
                  left: screenSize.width / 10, right: MEDIUM_SPACE),
              child: AutoSizeText(
                appLocalizations.offUtility,
                maxLines: 2,
                style: Theme.of(context)
                    .textTheme
                    .headline1!
                    .apply(color: const Color.fromARGB(255, 51, 51, 51)),
              ),
            ),
          ),
          const Spacer(flex: 1),
          Flexible(
            flex: 1,
            child: Padding(
              padding:
                  EdgeInsets.symmetric(horizontal: screenSize.width / 10),
              child: Row(
                mainAxisAlignment: MainAxisAlignment.spaceBetween,
                children: <Widget>[
                  SvgPicture.asset(
                    'assets/onboarding/nutriscore-a-no-bg.svg',
                    width: 80,
                  ),
                  SvgPicture.asset(
                    'assets/onboarding/ecoscore-a-no-bg.svg',
                    width: 80,
                  ),
                ],
              ),
            ),
          ),
          const Spacer(flex: 2),
        ],
      ),
      const Positioned(
        child: Align(
          alignment: Alignment.bottomCenter,
          child: NextButton(OnboardingPage.SCAN_EXAMPLE),
        ),
      ),
    ],
  );
}