我试图从火堆获取数据，但在 Flutter 上显示此错误"The instance member 'mapRecords' can't be accessed in an initializer

Question

我试图从firestore获取数据，但显示了此错误"无法在初始值设定项中访问实例成员"mapRecords"Flutter上。

错误的屏幕截图

https://drive.google.com/drive/folders/1toBdn9h4-LgBLl5ybG63brgXmk5G0h3F?usp=sharing

我的代码

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:hexcolor/hexcolor.dart';
import 'package:kathana/utils/config.dart';
import '../screens/wordsBefore18/database/words12model.dart';
class uitry5 extends StatefulWidget {
const uitry5({Key? key}) : super(key: key);
@override
State<uitry5> createState() => _uitry5State();
}
class _uitry5State extends State<uitry5> {
List<String> wordList = [];
Future _fetch = Future(() async {
var records = await FirebaseFirestore.instance.collection('12words').get();
return mapRecords(records);
});
List<Words12> mapRecords(QuerySnapshot<Map<String, dynamic>> records) {
var wordList = records.docs
.map(
(words12) {
print(words12);
return
Words12(
id: words12.id,
wordName: words12['wordName'],
categoryName: words12['categoryName']
);}
.toList();
return wordList;
}
@override
void initState() {
super.initState();
print(wordList);
}
List<String> selectedWord = [];
List<String>? deSelectedWord = [];
@override
Widget build(BuildContext context) {
double height = MediaQuery.of(context).size.height;
double width = MediaQuery.of(context).size.width;
return Scaffold(
body: Container(
decoration: const BoxDecoration(
image: DecorationImage(
image: AssetImage(Config.app_background4), fit: BoxFit.fill),
),
child: SafeArea(
child: Center(
child: Column(
children: <Widget>[
Padding(
padding: const EdgeInsets.only(top: 14, right: 0),
child: Column(
children: [
SizedBox(
width: width * 0.94,
height: height * 0.30,
child: Column(
children: <Widget>[
const SizedBox(height: 16),
Wrap(
children: wordList.map(
(word) {
bool isSelected = false;
if (selectedWord!.contains(word)) {
isSelected = true;
}
return GestureDetector(
onTap: () {
if (!selectedWord!.contains(word)) {
if (selectedWord!.length < 50) {
selectedWord!.add(word);
deSelectedWord!.removeWhere(
(element) => element == word);
setState(() {});
print(selectedWord);
}
} else {
selectedWord!.removeWhere(
(element) => element == word);
deSelectedWord!.add(word);
setState(() {
// selectedHobby.remove(hobby);
});
print(selectedWord);
print(deSelectedWord);
}
},
child: Container(
margin: const EdgeInsets.symmetric(
horizontal: 5, vertical: 4),
child: Container(
padding: const EdgeInsets.symmetric(
vertical: 5, horizontal: 12),
decoration: BoxDecoration(
color: isSelected
? HexColor('#0000FF')
: HexColor('#D9D9D9'),
borderRadius:
BorderRadius.circular(18),
border: Border.all(
color: isSelected
? HexColor('#0000FF')
: HexColor('#D9D9D9'),
width: 2)),
child: Text(
word,
style: TextStyle(
color: isSelected
? Colors.black
: Colors.black,
fontSize: 14,
fontWeight: FontWeight.w600),
),
),
),
);
},
).toList(),
),

],
),
),
],
),
),
],
))),
),
);
}
}

型号

import 'dart:convert';
Words12 words12FromJson(String str) => Words12.fromJson(json.decode(str));
String words12ToJson(Words12 data) => json.encode(data.toJson());
class Words12 {
Words12({
required this.id,
required this.wordName,
required this.categoryName,
});
String id;
String wordName;
String categoryName;
factory Words12.fromJson(Map<String, dynamic> json) => Words12(
id: json["id"],
wordName: json["wordName"],
categoryName: json["categoryName"],
);
Map<String, dynamic> toJson() => {
"id": id,
"wordName": wordName,
"categoryName": categoryName,
};
}

如何解决此问题并从数据库中获取数据

Answer 1

您可以在future之前使用late。

late Future _fetch = ...

此外，我更喜欢将来在_fetch和FutureBuilder之前移动mapRecords。