请问我在这里做错了什么。我试图在扩展面板列表中有一个列表视图，如果我只渲染两个扩展列表，则代码运行不会出现错误。但如果我渲染了两个以上，并且我尝试展开任何其他面板列表，它会返回以下错误： RangeError (RangeError (index): Invalid value: Not in Included range 0..1: 2.
\n下面是我的代码示例。谢谢你们。
\n ExpansionPanelList(\n children: [\n ExpansionPanel(\n isExpanded: _isOpen[0],\n headerBuilder: (context, isOpen) {\n return Row(\n children: [\n SizedBox(width: 10.w),\n Center(\n child: Text(\n "Ball Games \xe2\x9a\xbd ",\n style: TextStyle(\n fontSize: 17.sp,\n fontWeight: FontWeight.w400,\n color: Color(0xff333333)),\n ),\n ),\n ],\n );\n },\n body: SingleChildScrollView(\n child: Column(\n mainAxisSize: MainAxisSize.min,\n children: [\n _myListView(),\n // _myListView(),\n ],\n ),\n ),\n ),\n ExpansionPanel(\n isExpanded: _isOpen[1],\n headerBuilder: (context, isOpen) {\n return Row(\n children: [\n SizedBox(width: 10.w),\n Center(\n …参数类型“void Function(String)”无法分配给参数类型“void Function(String?)?”。dartargument_type_not_assignable String newValue。你好，我在尝试在 flutter 中实现下拉列表菜单时遇到上述错误
下面是我的代码。拜托，我是颤振的新手
class _CreateAccountState extends State<CreateAccount> {
String dropdownvalue = 'Apple';
var items = ['Apple','Banana','Grapes','Orange','watermelon','Pineapple'];
@override
Widget build(BuildContext context) {
double h = MediaQuery.of(context).size.height;
double w = MediaQuery.of(context).size.width;
return Scaffold( ....
child: DropdownButton(
value: dropdownvalue,
icon: Icon(Icons.keyboard_arrow_down),
items:items.map((String items) {
return DropdownMenuItem(
value: items,
child: Text(items)
);
}
).toList(),
onChanged: (String newValue){
setState(() {
dropdownvalue = newValue;
});
},
),
谢谢你们。