Flutter ScrollablePositionedList无法跳转指定索引问题求助

核心问题1：跳转索引参数错误 #

点击按钮时调用controller.jumpTo(index: index)，但此处的index未定义——循环变量是i，应该传入i作为目标索引。

核心问题2：列表项数量配置错误 #

ScrollablePositionedList的itemCount写成了totalItems.length，但从循环逻辑看totalItems是一个整数（代表总条目数），而非列表，直接使用totalItems即可。

顶部按钮上滑隐藏的实现 #

要实现顶部数字列表上滑隐藏，需要将顶部区域与滚动列表结合，用NestedScrollView配合SliverAppBar来实现滚动时的隐藏效果。

修正后的完整代码 #

import 'dart:math';
import 'package:flutter/material.dart';
import 'package:flutter_widgets/flutter_widgets.dart';

class ScrollableListDemo extends StatelessWidget {
  final int totalItems = 20;
  final ItemScrollController controller = ItemScrollController();

  ScrollableListDemo({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: NestedScrollView(
        headerSliverBuilder: (context, innerBoxIsScrolled) {
          return [
            SliverAppBar(
              pinned: false,
              floating: false,
              expandedHeight: 100,
              flexibleSpace: FlexibleSpaceBar(
                centerTitle: true,
                title: const Text("Click the number below to jump to Index"),
                background: Wrap(
                  alignment: WrapAlignment.center,
                  children: [
                    for (int i = 0; i < totalItems; i++)
                      InkWell(
                        onTap: () {
                          controller.jumpTo(index: i);
                        },
                        child: Padding(
                          padding: const EdgeInsets.all(8.0),
                          child: Text(
                            (i).toString(),
                            style: const TextStyle(
                                fontSize: 18, fontWeight: FontWeight.bold),
                          ),
                        ),
                      )
                  ],
                ),
              ),
            )
          ];
        },
        body: ScrollablePositionedList.builder(
          itemScrollController: controller,
          itemCount: totalItems,
          itemBuilder: (context, index) {
            return ConstrainedBox(
              constraints: const BoxConstraints(minHeight: 50, maxHeight: 200),
              child: Container(
                color: Color.fromARGB(
                    255,
                    Random().nextInt(255),
                    Random().nextInt(255),
                    Random().nextInt(255)),
                height: 100.0 * index * 0.1,
                child: ListTile(
                  title: Text(
                    "Item $index",
                    style: const TextStyle(
                        fontSize: 24, fontWeight: FontWeight.bold),
                  ),
                ),
              ),
            );
          },
        ),
      ),
    );
  }
}

内容的提问来源于stack exchange，提问作者Joven Dev