如何在 IntroductionScreen 小部件 Flutter 中制作全屏渐变色

我是Flutter 翼新手.我想用IntroductionScreen小工具来制作全屏渐变背景色.然而，当我在盒子装饰中使用渐变 colored颜色 时，底部有白色的盒子空间.我不希望这种事发生.这是我的代码

return IntroductionScreen(
  pages: [
    PageViewModel(
      title: "Hallo1",
      body:
          "Instead of having to buy an entire share, invest any amount you want.",
      image: buildImage('assets/onboard1bg.png'),
      decoration: buildDecoration(),
    ),
    PageViewModel(
      title: "Hallo2",
      body:
          "Instead of having to buy an entire share, invest any amount you want.",
      image: buildImage('assets/onboard2bg.png'),
      decoration: buildDecoration(),
    ),
  ],
  showNextButton: false,
  showDoneButton: false,
  showSkipButton: false,
  dotsDecorator: getDotDecoration(),
  globalFooter: Padding(
    padding: const EdgeInsets.symmetric(horizontal: 20),
    child: Column(
      children: [
        ElevatedButton(
          child: Text(
            'Login',
            style: TextStyle(color: Colors.white),
          ),
          onPressed: () {
            CupertinoModalBottom(context, "Login", SignIn(), true);
          },
          style: ElevatedButton.styleFrom(
            minimumSize: const Size.fromHeight(50),
            primary: Colors.orange,
            shape: RoundedRectangleBorder(
              borderRadius: BorderRadius.circular(12),
            ),
          ),
        ),
      ],
    ),
  ),
);
  }

  DotsDecorator getDotDecoration() => DotsDecorator(
        color: Colors.grey,
        size: Size(15, 8),
        activeColor: Colors.white,
        activeSize: Size(25, 8),
        activeShape: RoundedRectangleBorder(
          borderRadius: BorderRadius.circular(24),
        ),
        shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.circular(24),
        ),
      );

  Widget buildImage(String path) => Center(child: Image.asset(path));

  PageDecoration buildDecoration() => PageDecoration(
        imagePadding: EdgeInsets.all(0),
        boxDecoration: BoxDecoration(
          gradient: LinearGradient(
            begin: Alignment.topLeft,
            end: Alignment.bottomRight,
            colors: [
              Color.fromRGBO(205, 193, 255, 1.0),
              Color.fromARGB(255, 255, 79, 10),
              Color.fromARGB(255, 255, 31, 31),
            ],
          ),
        ),
      );
}

这就是它看起来的样子，我想做渐变色全屏.但是，并没有奏效