Flutter调用showModalBottomSheet报错：Invalid constant value及Invalid function

错误原因 #

1. Invalid function 错误：onPressed回调里错误地把showModalBottomSheet函数调用的结果赋值给自身，这是语法错误——函数调用不需要赋值操作。
2. Invalid constant value 错误：FloatingActionButton未声明为const，但它的child属性使用了const Icon，常量修饰符不匹配导致冲突。

修复后的代码 #

import 'package:flutter/material.dart';
import 'package:todoey/screen/tasks_list.dart';

class TasksScreen extends StatelessWidget {
  Widget buildBottomSheet(BuildContext context) {
    return Container();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.lightBlueAccent,
      floatingActionButton: FloatingActionButton(
        backgroundColor: Colors.lightBlueAccent,
        child: Icon(Icons.add), // 移除const修饰符
        onPressed: () {
          // 直接调用showModalBottomSheet，无需赋值
          showModalBottomSheet(
            context: context,
            builder: buildBottomSheet,
          );
        },
      ),
      body: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: <Widget>[
          Container(
            padding: const EdgeInsets.only(
                top: 60.0, left: 30, right: 30, bottom: 30.0),
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.start,
              children: const <Widget>[
                CircleAvatar(
                  child: Icon(
                    Icons.list,
                    size: 30,
                    color: Colors.lightBlueAccent,
                  ),
                  backgroundColor: Colors.white,
                  radius: 30,
                ),
                SizedBox(height: 10),
                Text(
                  'Todoey',
                  style: TextStyle(
                    color: Colors.white,
                    fontSize: 50,
                    fontWeight: FontWeight.w700,
                  ),
                ),
                Text(
                  '12 task',
                  style: TextStyle(
                    color: Colors.white,
                  ),
                ),
              ],
            ),
          ),
          Expanded(
            child: Container(
              padding: const EdgeInsets.symmetric(horizontal: 20),
              decoration: const BoxDecoration(
                borderRadius: BorderRadius.only(
                    topLeft: Radius.circular(30.0),
                    topRight: Radius.circular(30)),
                color: Colors.white,
              ),
              child: const TasksList(),
            ),
          ),
        ],
      ),
    );
  }
}

额外提示 #

• 修正了原代码中buildButtomSheet的拼写错误（改为buildBottomSheet），属于代码规范优化。
• 如果需要处理底部弹窗关闭后的返回结果，可将onPressed改为异步回调：

  onPressed: () async {
    final result = await showModalBottomSheet(
      context: context,
      builder: buildBottomSheet,
    );
    // 在这里处理返回的result
  },
  

内容的提问来源于stack exchange，提问作者Jamiekazi