使用ExpansionPanel小工具。
您需要创建一个变量并保持扩展面板索引的扩展状态。

expansionCallback: (int index, bool isExpanded) {
        setState(() {
          // when any of expansionPanel is Tapped
          // set all expansion to false
          for(int i = 0; i<_data.length; i++){
            _data[i].isExpanded = false;
          }
          // then set the tapped index to its state
          _data[index].isExpanded = !isExpanded;
        });
      },

Here is an live demo for expansion panel

试试这个：
创建变量：第一个月
和listview：

ListView.builder(
          itemCount: 10,
          shrinkWrap: true,
          itemBuilder: (BuildContext context, findex) {
            return ExpansionTile(
              initiallyExpanded: findex == selected,
              key: Key(selected.toString()),
              title: Text(userList[findex].parentdata[0].title,
                style: TextStyle(fontSize: 15.0, fontWeight: FontWeight.bold,color: Colors.black),
              ),
              onExpansionChanged: (newState) {
                setState(() {
                  selected = findex;
                });
              },
              children: [
                ListView.builder(
                  itemCount: 10,
                  shrinkWrap: true,
                  itemBuilder: (BuildContext context, sindex) {
                    return ListTile(
                      title: Text(
                        userList[findex].document[sindex].title,
                        style: TextStyle(fontSize: 15.0, fontWeight: FontWeight.bold,color: Colors.black),
                      ),
                      onTap: () {
                        print(userList[findex].document[sindex].title);
                      },
                    );
                  },
                ),
              ],
            );
          },
        ),

尝试以下代码
声明一个int变量

int selectedTile = -1;

您的小工具

ListView.builder(
  key: Key(selectedTile.toString()),
  itemCount: 5,
  itemBuilder: (context, index) {
    return ExpansionTile(
      key: Key(index.toString()),
      initiallyExpanded: index == selectedTile,
      title: Text('ExpansionTile $index'),
      subtitle: Text('Trailing expansion arrow icon'),
      children: [
        ListTile(
          title: Text('This is tile number $index'),
        ),
      ],
      onExpansionChanged: ((newState) {
        if (newState)
          setState(() {
            selectedTile = index;
          });
        else
          setState(() {
            selectedTile = -1;
          });
      }),
    );
  },
);

确保ExpansionTile位于有状态微件中

ListView.builder(
                        itemCount: 5,
                          shrinkWrap: true,
                          itemBuilder: (BuildContext context, index) {
                            return CustomExpansionTile(index: index);
                          },
                        ),

//扩展平铺窗口小部件

class CustomExpansionTile extends StatefulWidget {
              final int index;
            
              const CustomExpansionTile({Key? key, required this.index}) : super(key: key);
            
              @override
              State<CustomExpansionTile> createState() => _CustomExpansionTileState();
            }
            
            class _CustomExpansionTileState extends State<CustomExpansionTile> {
              int selectedIndexExpansionTile = -1;
            
              @override
              Widget build(BuildContext context) {
                return ExpansionTile(
                    initiallyExpanded: widget.index == selectedIndexExpansionTile,
                    key: Key(selectedIndexExpansionTile.toString()),
                    title: Text(
                      widget.index.toString(),
                    ),
                    onExpansionChanged: (newState) {
                 
                      if (newState) {
                        selectedIndexExpansionTile = widget.index;
                      } else {
                        selectedIndexExpansionTile = -1;
                      }
                      setState(() {});
                    },
                    children: [Text(widget.index.toString())]);
              }
            }