Flutter运行报错Expected a class member. :19 问题排查求解

• 语法错误出现在Scaffold组件的参数配置段：你提前闭合了AppBar构造方法的括号，将本属于AppBar的title参数直接暴露在Scaffold的参数列表中。由于Scaffold本身没有title这个合法参数，Dart语法解析时无法识别这个游离的属性，就抛出了「Expected a class member. :19」的报错。

将title属性移动到AppBar的构造方法内部，删除AppBar()后面多余的闭合括号即可，修复后的完整代码如下：

import 'package:flutter/material.dart';

// 已同步将类名调整为Dart规范要求的大驼峰格式，避免后续规范警告
class LoginScreen extends StatelessWidget {
  const LoginScreen({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      bottomSheet: const Text(
        'Hello',
      ),
      appBar: AppBar(
        title: const Text(
          'Hello',
        ),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children:
          [
            Row(
              children:
              [
                Column(
                  mainAxisSize: MainAxisSize.max,
                  mainAxisAlignment: MainAxisAlignment.center,
                  children:
                  const [
                   Text(
                     'Hello AbdelAzim',
                     style: TextStyle(
                       fontWeight: FontWeight.bold,
                       fontSize: 30,
                     ),
                   ),

                  ],
                ),
              ],
            ),
          ],
        ),
      ),

      );
  }
}

内容的提问来源于stack exchange，提问作者Abdelazim Showman