Flutter问题：ListWheelScrollView下StatefulWidget无法更新按钮显示月份

核心问题 #

你的代码存在两个关键问题导致按钮无法显示选中的月份：

1. ElevatedButton的Text内容为空：你直接写了Text('')，没有绑定需要展示的currentState变量。
2. currentState初始化索引错误：DateTime.now().month返回1-12的数值，直接作为列表索引会导致初始月份显示错误（列表索引范围是0-11）。

修正后的完整代码 #

import 'package:flutter/material.dart';
import 'year_month_picker/states_month.dart';
import 'year_month_picker/widgets/wheeltile.dart';

class MyMonthPickerr extends StatefulWidget {
  const MyMonthPickerr({Key? key}) : super(key: key);
  @override
  _MyMonthPickerrState createState() => _MyMonthPickerrState();
}

class _MyMonthPickerrState extends State<MyMonthPickerr> {
  List<States_Month> states_month = [];
  // 修正索引：month减1，匹配列表0-11的索引范围
  String currentState = [
    'January',
    'February',
    'March',
    'April',
    "May",
    "June",
    "July",
    'August',
    "September",
    "October",
    'November',
    'December'
  ][DateTime.now().month - 1];

  @override
  void initState() {
    super.initState();
    states_month = allStates();
  }

  @override
  Widget build(BuildContext context) {
    return Center(
      child: ElevatedButton(
        // 绑定currentState，让按钮实时显示选中月份
        child: Text(currentState),
        onPressed: () => showModalBottomSheet(
          context: context,
          builder: (BuildContext context) {
            // 同步初始选中索引，避免模态框和按钮状态错位
            int selectedIndex = states_month.indexWhere((state) => state.names == currentState);
            return Container(
              color: Colors.blueGrey.shade800,
              child: ListWheelScrollView.useDelegate(
                itemExtent: 50,
                controller: FixedExtentScrollController(
                  initialItem: selectedIndex,
                ),
                perspective: 0.001,
                diameterRatio: 1.6,
                physics: FixedExtentScrollPhysics(),
                squeeze: 1.0,
                overAndUnderCenterOpacity: 0.2,
                useMagnifier: true,
                magnification: 1.3,
                onSelectedItemChanged: (index) {
                  setState(() {
                    currentState = states_month[index].names!;
                  });
                },
                childDelegate: ListWheelChildBuilderDelegate(
                  childCount: states_month.length,
                  builder: (context, index) {
                    return WheelTile(
                      currentState == states_month[index].names
                          ? Colors.white
                          : Colors.white60,
                      states_month[index].names!,
                    );
                  },
                ),
              ),
            );
          },
        ),
      ),
    );
  }
}

额外优化说明 #

• 模态框初始化时，通过indexWhere获取当前currentState对应的索引，确保滚动轮初始位置和按钮显示的月份完全一致。
• 移除了冗余的括号和类型转换（((DateTime.now().month)).toInt()），DateTime.now().month本身就是int类型，无需额外转换。

内容的提问来源于stack exchange，提问作者Mathieu