您可以创建一个helper方法来代替StatelessWidget，因为如果所需的类型是TextButton?，那么使用StatelessWidget时，您应该扩展或实现TextButton类型：

class SnackbarTextButton extends TextButton {// ...}

但是这会给您的案例带来额外的不必要的工作，因为您可以简单地创建一个helper方法来返回您想要的TextButton小部件：

TextButton snackbarTextButton ({required this.text}) {
 return TextButton(
  style: ButtonStyle(
    overlayColor: MaterialStateColor.resolveWith((states) => Colors.transparent),
    splashFactory: NoSplash.splashFactory,
  ),
  onPressed: () {},
  child: Text(
    text,
    style: const TextStyle(
      fontSize: 12,
      color: Colors.white,
      fontWeight: FontWeight.bold,
    ),
  ),
);
 }

那么就这样命名它：

snackbarTextButton(text: "exampleText"), // this will be valid for TextButton type

我希望这个答案能解决你的错误这是你应该做的
用于main.dart

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return GetMaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Snackbar'),
    );
  }
}

您可以像这样使用Get.showSnackbar

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text(widget.title), actions: [
        TextButton(
            onPressed: () {
              Get.showSnackbar(const GetSnackBar(
                backgroundColor: Colors.blue,
                titleText: SnackbarTextButton(text: "SnackbarTextButton"),
                message: "Hello",
              ));
            },
            child: const Text(
              "Show snackBar",
              style: TextStyle(color: Colors.white),
            )),
      ]),
      body: Column(children: <Widget>[]),
    );
  }
}

文本按钮代码

class SnackbarTextButton extends StatelessWidget {
  final String text;

  const SnackbarTextButton({Key? key, required this.text}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Align(
      alignment: Alignment.centerLeft,
      child: TextButton(
        style: ButtonStyle(
          backgroundColor:
              MaterialStateColor.resolveWith((states) => Colors.red),
          overlayColor:
              MaterialStateColor.resolveWith((states) => Colors.transparent),
          splashFactory: NoSplash.splashFactory,
        ),
        onPressed: () {
          Get.back();
        },
        child: Text(
          text,
          style: const TextStyle(
            fontSize: 12,
            color: Colors.white,
            fontWeight: FontWeight.bold,
          ),
        ),
      ),
    );
  }
}

输出：