Flutter移除列表项后ExpansionTile触发类型转换错误

移除列表项后抛出以下错误：

The following _CastError was thrown building SingleChildScrollView(dependencies:
[PrimaryScrollController]):
type 'bool' is not a subtype of type 'double?' in type cast

The relevant error-causing widget was: 
When the exception was thrown, this was the stack: 
#0      ScrollPosition.restoreScrollOffset (package:flutter/src/widgets/scroll_position.dart:420:103)
#1      new ScrollPosition (package:flutter/src/widgets/scroll_position.dart:105:7)
#2      new ScrollPositionWithSingleContext (package:flutter/src/widgets/scroll_position_with_single_context.dart:56:8)
#3      ScrollableState._updatePosition (package:flutter/src/widgets/scrollable.dart:406:10)
#4      ScrollableState.didChangeDependencies (package:flutter/src/widgets/scrollable.dart:431:5)

相关代码 #

列表定义：

List<dynamic> RefrigCarNo = [];

ListView构建代码：

ListView.builder(
        shrinkWrap: true,
        itemCount: RefrigCarNo.length,
        itemBuilder: (BuildContext context, int index) {
          return Card(
            color: getColor(context, index),
            key: new PageStorageKey(RefrigCarNo[0].elementAt(index)), // 此处key设置存在问题
            child: ExpansionTile(
              maintainState: CollapseState,
              title: RichText(
                  textDirection: TextDirection.rtl,
                  text: TextSpan(
                      style: label_A,
                      children: [
                        TextSpan(text: 'refrigCar'),
                        TextSpan(text: ' ${RefrigCarNo[index][1].toString()} ')
                      ]
                  )
              ),
              children: [
                Row(
              mainAxisAlignment: MainAxisAlignment.center,
              children: [
                Container(
                  margin: EdgeInsets.fromLTRB(0, 10, 0, 3),
                  width: PageWidth * 0.4,
                  color: Colors.white,
                  child: Column(
                    children: [
                      Text('Kg Of Material', style: label_A,),
                      AppTextField1(
                        MyController: Weight,
                        MyValidation: false,
                        typeOfInput: TextInputType.number,
                        myReadOnly: readOnlyChange,
                      ),
                    ],
                  ),
                ),
                Container(
                  margin: EdgeInsets.fromLTRB(0, 10, 0, 3),
                  width: PageWidth * 0.3,
                  color: Colors.white,
                  child: Column(
                    children: [
                      Text('Total Net', style: label_A,),
                      AppTextField1(
                        MyController: NetCalcWeight,
                        MyValidation: false,
                        typeOfInput: TextInputType.number,
                        myReadOnly: readOnlyChange,
                      ),
                    ],
                  ),
                ),
              ],
            ),
              ],
            ),
          );
        }),

删除列表项函数：

void onDeleteVar(int _index) async{ 
 setState(() {
  RefrigCarNo.removeAt(_index);
  });
}

解决方案 #

错误根源是PageStorageKey重复/冲突，导致滚动偏移量的存储被ExpansionTile的bool类型展开状态覆盖，进而触发类型转换错误。按以下步骤修复：

1. 保证PageStorageKey的唯一性
   给Card和ExpansionTile分别设置独立的唯一key，避免键冲突：

   return Card(
     color: getColor(context, index),
     key: PageStorageKey('card_refrig_car_${RefrigCarNo[index][1]}'),
     child: ExpansionTile(
       key: PageStorageKey('expansion_refrig_car_${RefrigCarNo[index][1]}'),
       maintainState: CollapseState,
       // ...其他原有代码
     ),
   );
   

2. 为每个列表项单独维护TextField控制器
   当前所有项复用同一个Weight和NetCalcWeight控制器，会导致状态混乱。修改列表结构，让每个元素自带专属控制器：

   // 添加新项的示例代码
   void addNewRefrigCar() {
     setState(() {
       RefrigCarNo.add({
         'carNo': '新车辆编号', // 替换为实际车辆标识
         'weightController': TextEditingController(),
         'netController': TextEditingController(),
       });
     });
   }
   

   然后在ListView中调用对应项的控制器：

   AppTextField1(
     MyController: RefrigCarNo[index]['weightController'],
     MyValidation: false,
     typeOfInput: TextInputType.number,
     myReadOnly: readOnlyChange,
   ),
   // ...
   AppTextField1(
     MyController: RefrigCarNo[index]['netController'],
     MyValidation: false,
     typeOfInput: TextInputType.number,
     myReadOnly: readOnlyChange,
   ),
   

3. 删除项时清理对应PageStorage数据
   删除列表项后，手动清理该项对应的PageStorage存储，并销毁控制器避免内存泄漏：

   void onDeleteVar(int _index) {
     final carId = RefrigCarNo[_index][1];
     // 清理Card和ExpansionTile的PageStorage数据
     PageStorage.of(context)?.writeState(context, null, identifier: PageStorageKey('card_refrig_car_$carId'));
     PageStorage.of(context)?.writeState(context, null, identifier: PageStorageKey('expansion_refrig_car_$carId'));
     // 销毁控制器
     RefrigCarNo[_index]['weightController'].dispose();
     RefrigCarNo[_index]['netController'].dispose();
     setState(() {
       RefrigCarNo.removeAt(_index);
     });
   }
   

内容的提问来源于stack exchange，提问作者Hamed Zahiri