如何解决这个错误？ 'List<Word?>' 不是 'val'E/flutter (29035) 的 'List<Word>' 类型的子类型：#0 RxObjectMixin
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【中文标题】如何解决这个错误？ \'List<Word?>\' 不是 \'val\'E/flutter (29035) 的 \'List<Word>\' 类型的子类型：#0 RxObjectMixin.value=【英文标题】：How to solve this error? 'List<Word?>' is not a subtype of type 'List<Word>' of 'val'E/flutter (29035): #0 RxObjectMixin.value=如何解决这个错误？ 'List<Word?>' 不是 'val'E/flutter (29035) 的 'List<Word>' 类型的子类型：#0 RxObjectMixin.value= 【发布时间】：2021-11-14 00:09:02 【问题描述】：我在 Controller 类中定义了一个名为 data 的变量。我在 fillWordlist 方法中收到了上面提到的错误。我在视图类的 historyWordList 方法中创建了 listview.builder。但列表没有出现在屏幕上，我收到此错误。 'List
控制器类
class WordController extends GetxController
TextEditingController controllerInput1 = TextEditingController();
TextEditingController controllerInput2 = TextEditingController();
RxBool active2 = false.obs;
final translator = GoogleTranslator();
RxList data = <Word>[].obs;
@override
void onInit()
fillWordList();
super.onInit();
onClickIconButtonFavori()
if (controllerInput1.text.isNotEmpty && controllerInput2.text.isNotEmpty)
addNote();
clear();
showText()
if (active2.value == true)
return;
active2.toggle();
ekle(Word word) async
var val = await WordRepo().add(word);
showDilog("Kayıt Başarılı");
update();
return val;
updateWord(Word word) async
var val = await WordRepo().update(word);
showDilog("Kayıt Başarılı");
return val;
deleteWord(int? id) async
var val = await WordRepo().deleteById(id!);
return val;
fillWordList() async
data.value = await WordRepo().getAll();
translateLanguage(String newValue) async
if (newValue == null || newValue.length == 0)
return;
List list = ["I", "i"];
if (newValue.length == 1 && !list.contains(newValue))
return;
var translate = await translator.translate(newValue, from: 'en', to: 'tr');
controllerInput2.text = translate.toString();
return translate;
showDilog(String message)
Get.defaultDialog(title: "Bilgi", middleText: message);
addNote() async
var word =
Word(wordEn: controllerInput1.text, wordTr: controllerInput2.text);
await ekle(word);
fillWordList();
clear()
controllerInput2.clear();
controllerInput1.clear();
updateNote() async
var word =
Word(wordEn: controllerInput1.text, wordTr: controllerInput2.text);
await updateWord(word);
await fillWordList();
update();
查看类：Main_page.dart
class MainPage extends StatelessWidget
String _firstLanguage = "English";
String _secondLanguage = "Turkish";
WordController controller = Get.put(WordController());
final _formKey = GlobalKey<FormState>();
@override
Widget build(BuildContext context)
return Scaffold(
drawer: _drawer,
backgroundColor: Colors.grey.shade300,
appBar: _appbar,
body: _bodyScaffold,
floatingActionButton: _floattingActionButton,
);
SingleChildScrollView get _bodyScaffold
return SingleChildScrollView(
child: Column(
children: [
chooseLanguage,
translateTextView,
//futureBuilder,
],
),
);
AppBar get _appbar
return AppBar(
backgroundColor: Colors.blueAccent,
centerTitle: true,
title: Text("TRANSLATE"),
elevation: 0.0,
);
get chooseLanguage => Container(
height: Get.height / 12.0,
decoration: buildBoxDecoration,
child: Row(
mainAxisAlignment: MainAxisAlignment.start,
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
firstChooseLanguage,
changeLanguageButton,
secondChooseLanguage,
],
),
);
get buildBoxDecoration
return BoxDecoration(
color: Colors.white,
border: Border(
bottom: BorderSide(
width: 3.5,
color: Colors.grey,
),
),
);
get translateTextView => Column(
children: [
Card(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(8.0)),
),
margin: EdgeInsets.only(left: 2.0, right: 2.0, top: 2.0),
child: _formTextField,
),
Obx(
() => Container(
height: controller.active2 == true
? Get.height / 2.3
: Get.height / 1.6,
child: historyWordList,
),
)
],
);
Widget get historyWordList
return ListView.builder(
itemCount: controller.data.length,
itemBuilder: (context, index)
return Card(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(5.0)),
),
margin: EdgeInsets.only(left: 8.0, right: 8.0, top: 0.8),
child: Container(
color: Colors.white30,
padding: EdgeInsets.only(left: 8.0, top: 8.0, bottom: 8.0),
child: Row(
crossAxisAlignment: CrossAxisAlignment.start,
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
Obx(()=>Column(
crossAxisAlignment: CrossAxisAlignment.start,
mainAxisAlignment: MainAxisAlignment.spaceAround,
children: [
firstText(controller.data[index].value),
secondText(controller.data[index].value),
],
)),
historyIconbutton,
],
),
),
);
,
);
get _formTextField
return Form(
key: _formKey,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Container(
color: Colors.white30,
height: Get.height / 6.0,
padding: EdgeInsets.only(left: 16.0, top: 8.0, bottom: 8.0),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
textFormFieldEntr, //one textfield
favoriIconButton,
],
),
),
textFormField, //burası kapandı // second
],
),
);
get textFormFieldEntr
return Flexible(
child: Container(
height: Get.height / 5.2,
child: TextFormField(
readOnly: true, //sadece okuma
onTap: ()
showMaterialBanner();
,
controller: controller.controllerInput1,
onChanged: (text)
if (text.isEmpty)
controller.active2(false);
else
controller.active2(true);
,
maxLines: 6,
decoration: InputDecoration(
hintText: "Enter",
contentPadding: const EdgeInsets.symmetric(vertical: 5.0),
),
),
),
);
void showMaterialBanner()
ScaffoldMessenger.of(Get.context!).showMaterialBanner(MaterialBanner(
backgroundColor: Colors.white,
content: Padding(
padding: const EdgeInsets.only(top: 40.0),
child: Column(
children: [
TextFormField(
controller: controller.controllerInput1,
maxLines: 7,
onChanged: (text)
controller.translateLanguage(text);
if (text.isNotEmpty)
controller.showText();
// controller.showText();
,
decoration: InputDecoration(
suffixIcon: IconButton(
onPressed: ()
if (controller.controllerInput1.text.length > 0)
controller.clear();
else
controller.clear();
closeBanner();
,
icon: Icon(Icons.clear),
),
contentPadding: const EdgeInsets.symmetric(vertical: 5.0),
),
),
SizedBox(height: Get.height / 6.0),
TextFormField(
controller: controller.controllerInput2,
maxLines: 7,
onTap: ()
if (controller.controllerInput1.text.isEmpty)
controller.clear();
else
controller.addNote();
closeBanner();
,
decoration: InputDecoration(
contentPadding: const EdgeInsets.symmetric(vertical: 5.0),
),
),
],
),
),
actions: [
IconButton(
onPressed: ()
closeBanner();
,
icon: Icon(null),
),
]));
void closeBanner()
ScaffoldMessenger.of(Get.context!).hideCurrentMaterialBanner();
get textFormField
return Obx(()
return Container(
child: Visibility(
visible: controller.active2.value, //false
child: Container(
color: Colors.white30,
height: Get.height / 5.2,
padding:
EdgeInsets.only(left: 16.0, right: 42.0, top: 8.0, bottom: 8.0),
child: TextFormField(
readOnly: true,
controller: controller.controllerInput2,
maxLines: 6,
decoration: InputDecoration(
contentPadding: const EdgeInsets.symmetric(vertical: 5.0),
),
),
),
),
);
);
IconButton get historyIconbutton
return IconButton(
onPressed: () ,
icon: Icon(Icons.history),
iconSize: 30.0,
);
Text firstText(Word word)
return Text(
"İngilizce: $word.wordEn ?? """,
style: TextStyle(
fontWeight: FontWeight.w600,
),
maxLines: 1,
overflow: TextOverflow.ellipsis,
);
get changeLanguageButton
return Material(
color: Colors.white,
child: IconButton(
icon: Icon(
Icons.wifi_protected_setup_rounded,
color: Colors.indigo,
size: 30.0,
),
onPressed: () ,
),
);
get secondChooseLanguage
return Expanded(
child: Material(
color: Colors.white,
child: InkWell(
onTap: () ,
child: Center(
child: Text(
this._secondLanguage,
style: TextStyle(
color: Colors.blue[600],
fontSize: 22.0,
),
),
),
),
),
);
get firstChooseLanguage
return Expanded(
child: Material(
color: Colors.white,
child: InkWell(
onTap: () ,
child: Center(
child: Text(
this._firstLanguage,
style: TextStyle(
color: Colors.blue[600],
fontSize: 22.0,
),
),
),
),
),
);
Text secondText(Word word)
return Text(
"Türkçe: $word.wordTr ?? """,
style: TextStyle(
fontWeight: FontWeight.w400,
),
maxLines: 1,
overflow: TextOverflow.ellipsis,
);
get favoriIconButton
return IconButton(
alignment: Alignment.topRight,
onPressed: controller.onClickIconButtonFavori,
icon: Icon(
Icons.forward,
color: Colors.blueAccent,
size: 28.0,
),
);
FloatingActionButton get _floattingActionButton
return FloatingActionButton(
onPressed: ()
Get.to(WordListPage());
,
child: Icon(
Icons.app_registration,
size: 30,
),
);
Drawer get _drawer
return Drawer(
child: ListView(
// Important: Remove any padding from the ListView.
padding: EdgeInsets.zero,
children: <Widget>[
userAccountsDrawerHeader,
drawerFavorilerim,
drawersettings,
drawerContacts,
],
),
);
ListTile get drawerContacts
return ListTile(
leading: Icon(Icons.contacts),
title: Text("Contact Us"),
onTap: ()
Get.back();
,
);
ListTile get drawersettings
return ListTile(
leading: Icon(Icons.settings),
title: Text("Settings"),
onTap: ()
Get.back();
,
);
ListTile get drawerFavorilerim
return ListTile(
leading: Icon(
Icons.star,
color: Colors.yellow,
),
title: Text("Favorilerim"),
onTap: ()
Get.to(FavoriListPage());
,
);
UserAccountsDrawerHeader get userAccountsDrawerHeader
return UserAccountsDrawerHeader(
accountName: Text("UserName"),
accountEmail: Text("E-mail"),
currentAccountPicture: CircleAvatar(
backgroundColor: Colors.grey,
child: Text(
"",
style: TextStyle(fontSize: 40.0),
),
),
);
【问题讨论】：
【参考方案1】：此错误是由于 null 安全性造成的。尝试在您在函数中传递的每个单词实例之后添加!
【讨论】：
它不工作。 你能在我的代码中发送示例代码吗？ 你可以尝试转换 RxList 数据 =以上是关于如何解决这个错误？ 'List<Word?>' 不是 'val'E/flutter (29035) 的 'List<Word>' 类型的子类型：#0 RxObjectMixin的主要内容，如果未能解决你的问题，请参考以下文章
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