Dart 在本地获取并存储json
我以前问过这个问题,但仍然没有取得多大进展。我试图从端点获取一个json格式的列表,并将其分配给一个实例,然后逐步执行Dart 在本地获取并存储json,dart,flutter,Dart,Flutter,我以前问过这个问题,但仍然没有取得多大进展。我试图从端点获取一个json格式的列表,并将其分配给一个实例,然后逐步执行 import 'package:flutter/material.dart'; import 'package:http/http.dart' as http; import 'dart:async'; import 'dart:convert'; import '../utils/quiz.dart'; import '../utils/question.dart'; Q
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
import 'dart:async';
import 'dart:convert';
import '../utils/quiz.dart';
import '../utils/question.dart';
Quiz quiz1 = Quiz([
Question(
question: 'What is 1x1',
option1: '2',
option2: '3',
option3: '4',
option4: '1',
answer: '1'),
Question(
question: 'What is 1x2',
option1: '2',
option2: '3',
option3: '4',
option4: '1',
answer: '1'),
Question(
question: 'What is 1x3',
option1: '2',
option2: '3',
option3: '4',
option4: '1',
answer: '1'),
Question(
question: 'What is 1x4',
option1: '2',
option2: '3',
option3: '4',
option4: '1',
answer: '1'),
Question(
question: 'What is 1x5',
option1: '5',
option2: '3',
option3: '4',
option4: '1',
answer: '1')
]);
class QuestionScreen extends StatefulWidget {
@override
_QuestionScreenState createState() => new _QuestionScreenState();
}
class _QuestionScreenState extends State<QuestionScreen> {
Quiz quiz;
Question currentQuestion;
String questionText;
int questionNumber;
bool isCorrect;
String option1;
String option2;
String option3;
String option4;
String answer;
int index;
int counter = 0;
int _selected;
String url = 'http://www.cloudace.io/questions';
void onChanged(int value) {
setState(() {
_selected = value;
});
}
List<Question> parseQuestions(String responseBody) {
final parsed = json.decode(responseBody).cast<Map<String, dynamic>>();
return parsed.map<Question>((json) => Question.fromJson(json)).toList();
}
Future<List<Question>> fetchQuestion(http.Client client) async {
final response = await client.get('http://www.cloudace.io/questions');
return parseQuestions(response.body);//return compute(parseQuestions, response.body);
}
Future assignQuiz() async {
quiz = Quiz(await fetchQuestion(http.Client()));
}
@override
void initState() {
super.initState();
assignQuiz();
print(quiz.toString());
}
@override
Widget build(BuildContext context) {
if (quiz != null) {
return Scaffold(
appBar: AppBar(
title: Text('Quiz'),
),
body: Container(
child: Column(
children: <Widget>[
Text(quiz.questions[counter].question),
RadioListTile(
value: 0,
groupValue: _selected,
onChanged: (int value) {
onChanged(value);
},
activeColor: Colors.red,
subtitle: Text(
quiz.questions[counter].option1,
)),
RadioListTile(
value: 1,
groupValue: _selected,
onChanged: (int value) {
onChanged(value);
},
activeColor: Colors.red,
subtitle: Text(
quiz.questions[counter].option2,
)),
RadioListTile(
value: 2,
groupValue: _selected,
onChanged: (int value) {
onChanged(value);
},
activeColor: Colors.red,
subtitle: Text(
quiz.questions[counter].option3,
)),
RadioListTile(
value: 3,
groupValue: _selected,
onChanged: (int value) {
onChanged(value);
},
activeColor: Colors.red,
subtitle: Text(
quiz.questions[counter].option4,
)),
RaisedButton(
child: Text('Press Me'),
onPressed: () {
print('counter is: $counter \n_selected is: $_selected');
setState(() {
onChanged(null);
if (counter < 5) {
counter++;
} else {
counter = 0;
}
});
})
],
),
),
);
} return Center(child: CircularProgressIndicator());}
}
导入“包装:颤振/材料.省道”;
将“package:http/http.dart”导入为http;
导入“dart:async”;
导入“dart:convert”;
导入“../utils/quick.dart”;
导入“../utils/question.dart”;
测验quiz1=测验([
问题:(
问题:“什么是1x1”,
选项1:“2”,
备选案文2:“3”,
选项3:“4”,
选项4:“1”,
答复:"一",,
问题:(
问题:“什么是1x2”,
选项1:“2”,
备选案文2:“3”,
选项3:“4”,
选项4:“1”,
答复:"一",,
问题:(
问题:“什么是1x3”,
选项1:“2”,
备选案文2:“3”,
选项3:“4”,
选项4:“1”,
答复:"一",,
问题:(
问题:“什么是1x4”,
选项1:“2”,
备选案文2:“3”,
选项3:“4”,
选项4:“1”,
答复:"一",,
问题:(
问题:“什么是1x5”,
选项1:“5”,
备选案文2:“3”,
选项3:“4”,
选项4:“1”,
答:"1")
]);
类QuestionScreen扩展StatefulWidget{
@凌驾
_QuestionScreenState createState()=>新建_QuestionScreenState();
}
类_QuestionScreenState扩展状态{
问答游戏;
问题-当前问题;
字符串文本;
整数;
布尔是正确的;
字符串选项1;
字符串选项2;
字符串选项3;
字符串选项4;
字符串回答;
整数指数;
int计数器=0;
int_选定;
字符串url='0http://www.cloudace.io/questions';
更改后的void(int值){
设置状态(){
_所选=值;
});
}
列出问题(字符串响应库){
final parsed=json.decode(responseBody.cast();
返回parsed.map((json)=>Question.fromJson(json)).toList();
}
将来的fetchQuestion(http.Client)异步{
最终响应=等待客户端。获取('http://www.cloudace.io/questions');
return parseQuestions(response.body);//return compute(parseQuestions,response.body);
}
Future assignquick()异步{
quick=quick(等待获取问题(http.Client());
}
@凌驾
void initState(){
super.initState();
分配测验();
打印(quick.toString());
}
@凌驾
小部件构建(构建上下文){
if(测验!=null){
返回脚手架(
appBar:appBar(
标题:文本(“测验”),
),
主体:容器(
子:列(
儿童:[
文本(测验.问题[计数器].问题),
放射科医师(
值:0,
groupValue:\u已选定,
onChanged:(int值){
一旦改变(价值);
},
activeColor:Colors.red,
字幕:文本(
测验。问题[柜台]。选项1,
)),
放射科医师(
价值:1,
groupValue:\u已选定,
onChanged:(int值){
一旦改变(价值);
},
activeColor:Colors.red,
字幕:文本(
测验。问题[柜台]。选项2,
)),
放射科医师(
价值:2,
groupValue:\u已选定,
onChanged:(int值){
一旦改变(价值);
},
activeColor:Colors.red,
字幕:文本(
测验。问题[柜台]。选项3,
)),
放射科医师(
价值:3,
groupValue:\u已选定,
onChanged:(int值){
一旦改变(价值);
},
activeColor:Colors.red,
字幕:文本(
测验。问题[柜台]。选项4,
)),
升起的按钮(
child:Text('Press Me'),
已按下:(){
打印('counter is:$counter\n\u selected is:$\u selected');
设置状态(){
onChanged(空);
如果(计数器<5){
计数器++;
}否则{
计数器=0;
}
});
})
],
),
),
);
}返回中心(子项:CircularProgressIndicator());}
}
如果我设置quick=quiz1,我将获得所需的行为,但使用future返回空值,那么在构建小部件之前,如何从json端点填充quick?使用initState似乎没有什么区别。将作业包装到
测验
中的设置状态
assignQuiz() async {
Quiz newQuiz = Quiz(await fetchQuestion(http.Client()));
setState(() {
quiz = newQuiz;
});
}
将作业包装到
测验
中的设置状态
assignQuiz() async {
Quiz newQuiz = Quiz(await fetchQuestion(http.Client()));
setState(() {
quiz = newQuiz;
});
}
谢谢这正是我想要的谢谢!这正是我想要的