我正在学习抖动,我想构建一个简单的应用程序,该应用程序可以在按下按钮时更新当天的报价。
因此,我将自动创建的默认Flutter应用程序和我在网上找到的教程结合了起来。
在加载应用程序时会显示报价,但是我不确定在按下按钮时如何更新报价。
我尝试将这一行放在_incrementCounter函数中,但是会引发错误:
_saying = Quote();
不能将类型为'Quote'的值赋给类型变量 “字符串”。
当我按下按钮时,是否还有报价更新?
谢谢!
-主要
import 'dart:async';
import 'dart:convert';
import 'package:flutter/material.dart';
import 'package:http/http.dart' as http;
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
@override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
final String title;
@override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
String _saying = '';
String url = 'https://quotes.rest/qod.json';
void _incrementCounter() {
setState(() {
_counter++;
_saying = Quote();
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text("-- Quote of the Day --"),
Quote(),
Text(
'dYou have pushed the buttons this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.display1,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}
class Quote extends StatelessWidget {
@override
Widget build(BuildContext context) {
return FutureBuilder(
future: _getQuote(),
builder: (context, snapshot) {
return snapshot.connectionState == ConnectionState.done
? Center(
child: Text(
snapshot.data,
textAlign: TextAlign.center,
))
: Center(child: CircularProgressIndicator());
});
}
}
Future<String> _getQuote() async {
final res = await http.get('http://quotes.rest/qod.json');
return json.decode(res.body)['contents']['quotes'][0]['quote'];
}
答案 0 :(得分:2)
您不需要_saying,像这样更改_incrementCounter
void _incrementCounter() {
setState(() {
_counter++;
});
}
由于使用setState,因此build方法将再次调用,然后将重新创建Quote,从而再次获取数据。我建议您稍后阅读并尝试使用更好的状态管理系统,例如provider和bloc。希望对您有帮助。