我想使用Parse_server_sdk查询数据，但收到此错误[错误：flutter/runtime/dart_vm_initializer. cc（41）]未处理的异常：延迟初始化错误：字段'_instance@597240915'尚未初始化。
它只发生在我调用initState（）的方法时，但如果我在elevatedButton中测试onPressed时，它可以被调用而没有错误。我不知道是什么问题，请有人帮助我。
这是调用查询的主屏幕代码：
import 'package:flutter/material.dart';
import 'package:flutter_simple_cms/api/parse_services.dart';
import 'package:flutter_simple_cms/screens/update_post_screen.dart';
import 'package:flutter_simple_cms/widgets/show_drawer.dart';
import 'package:flutter_simple_cms/widgets/show_snackbar.dart';
import 'package:parse_server_sdk_flutter/parse_server_sdk.dart';
class HomeScreen extends StatefulWidget {
const HomeScreen({super.key});
@override
State<HomeScreen> createState() => _HomeScreenState();
}
class _HomeScreenState extends State<HomeScreen> {
List<ParseObject> getPostList = [];
Future<List<ParseObject>>? testGetPost;
bool isDeleting = false;
@override
void initState() {
super.initState();
getDataTest();
}
void getDataTest() async {
testGetPost = ParseService().getPostsFuture();
print(testGetPost);
}
@override
Widget build(BuildContext context) {
return SafeArea(
child: Scaffold(
appBar: AppBar(
title: const Text('Home'),
),
drawer: showDrawer(context),
body: testBody(),
),
);
}
Widget testBody() {
return SizedBox(
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
child: Center(
child: ElevatedButton(
child: const Text('test'),
onPressed: () {
getDataTest();
},
),
),
);
}
Widget _body() {
return SizedBox(
height: MediaQuery.of(context).size.height,
width: MediaQuery.of(context).size.width,
child: StreamBuilder<List<ParseObject>>(
initialData: getPostList,
stream: ParseService().getPosts(),
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.waiting) {
return const Center(
child: SizedBox(
height: 75.0,
width: 75.0,
child: CircularProgressIndicator(),
),
);
} else if (snapshot.connectionState == ConnectionState.done) {
if (snapshot.hasError) {
return Center(
child: ElevatedButton(
child: const Text("Refresh"),
onPressed: () {
setState(() {});
},
));
}
if (snapshot.hasData) {
if (snapshot.data!.isEmpty) {
return const Center(
child: Text('NO DATA', style: TextStyle(fontSize: 36.0)),
);
}
return ListView.builder(
padding: const EdgeInsets.only(top: 10.0),
itemCount: snapshot.hasData ? snapshot.data!.length : 1,
itemBuilder: (BuildContext context, int index) {
if (snapshot.data!.isEmpty) {
return SizedBox(
width: MediaQuery.of(context).size.width,
height: MediaQuery.of(context).size.height,
child: const Center(
child: Text(
'Data is Empty!',
style: TextStyle(fontSize: 36.0),
),
),
);
}
final postData = snapshot.data![index];
ParseFile? postImageCover =
snapshot.data![index].get<ParseFile>('postImageCover');
final postTitle = postData.get<String>('postTitle')!;
final postContent = postData.get<String>('postContent')!;
return Card(
elevation: 7.0,
clipBehavior: Clip.hardEdge,
shape: RoundedRectangleBorder(
side: BorderSide(
color: Theme.of(context).colorScheme.primaryContainer,
width: 1.5,
),
borderRadius:
const BorderRadius.all(Radius.circular(15.0)),
),
child: Padding(
padding: const EdgeInsets.all(10.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Container(
alignment: Alignment.centerRight,
child: PopupMenuButton(
itemBuilder: (context) {
return [
PopupMenuItem(
value: 0,
child: Row(
children: const [
Icon(Icons.edit_note),
SizedBox(
// sized box with width 10
width: 10,
),
Text("Edit post")
],
),
),
PopupMenuItem(
value: 1,
child: Row(
children: const [
Icon(Icons.delete),
SizedBox(
// sized box with width 10
width: 10,
),
Text("Delete post")
],
),
),
];
},
onSelected: (value) {
if (value == 0) {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) =>
UpdatePost(postObject: postData),
),
);
} else {
isDeleting = true;
ParseService()
.deletePost(postData.objectId)
.then((response) {
if (response.success) {
setState(() => isDeleting = false);
showSnackbar(
context,
'Post Deleted!',
Colors.greenAccent,
Icons.check_circle_outline,
Colors.greenAccent,
);
} else {
isDeleting = false;
showSnackbar(
context,
response.error?.message,
Colors.red,
Icons.error_outline,
Colors.red,
);
}
});
}
},
),
),
addSpace(10.0),
Visibility(
visible: postImageCover != null,
child: SizedBox(
width: MediaQuery.of(context).size.width,
height: 300.0,
child: postImageCover == null
? null
: Image.network(
loadingBuilder:
(context, child, loadingProgress) {
if (loadingProgress == null) {
return child;
}
return const Center(
child: SizedBox(
height: 50.0,
width: 50.0,
child: CircularProgressIndicator(),
),
);
},
postImageCover.url!,
fit: BoxFit.cover,
),
),
),
addSpace(10.0),
Text(
postTitle,
textAlign: TextAlign.center,
style: const TextStyle(fontSize: 20.0),
),
addSpace(10.0),
Text(
postContent,
textAlign: TextAlign.center,
style: const TextStyle(fontSize: 16.0),
),
addSpace(5.0),
],
),
),
);
},
);
} else {
return const Center(
child: Text('NO DATA', style: TextStyle(fontSize: 36.0)),
);
}
} else {
return Text('State: ${snapshot.connectionState}');
}
},
),
);
}
Widget addSpace(double? heightVal) => SizedBox(height: heightVal);
}这是主屏幕调用的查询方法：
Future<List<ParseObject>> getPostsFuture() async {
QueryBuilder<ParseObject> queryPosts =
QueryBuilder<ParseObject>(ParseObject('PostList'));
final ParseResponse apiResponse = await queryPosts.query();
if (apiResponse.success && apiResponse.results != null) {
return Future.value(apiResponse.results as List<ParseObject>);
} else {
return [];
}
}我还尝试将其放在FutureBuilder上，认为查询无法在initState中调用，这很奇怪，因为很久以前，在flutter和Parse_server_sdk的旧版本上，当在initState中调用查询时，我的其他应用程序没有问题，但即使使用FutureBuilder，查询仍然无法在第一次构建时调用，它在snapshot.hasError.上卡住了。我将其更改为streamBuilder，但在第一次构建时也是如此，因此我只是放置了一个按钮来刷新，以获取第一次启动/构建时的数据
1条答案
按热度按时间z9smfwbn1#
我自己设法修好了，所以我会给任何遇到类似问题的人我的答案。首先，类ParseObject出现LateInitializationError的问题是因为Parse.initialize还没有完成，但类homescreen.dart立即被调用，可能是因为Parse.initialize在他自己的类上。所以对于像我一样的人，你可以把Parse.initialize放在它上面。如果你有同样的问题，这可能会有帮助。
所以为了解决这个问题，我首先将Parse.initialize打开的类改为Future，以返回Parse类的值。
就像这样：
然后在main.dart文件上修改void main（）中的Parse.initialize。
就像这样：
我希望我的回答能有所帮助