我正在创建一个双重listView应用程序，到目前为止运行良好，但是遇到了我似乎无法解决的问题。
我遇到错误[dart] 2 required argument(s) expected, but 0 found.
在我看来，这应该很容易解决，我以为我只需要改变...
body: _cryptoWidget(),
到...
body: _cryptoWidget(currency, color),
这没有用，但我仍然收到上述错误。
这是我用来激发错误的代码；
import 'package:flutter/material.dart';
import 'background.dart';
import 'package:flutter/foundation.dart';
import 'package:cryptick_nice_ui/data/crypto_data.dart';
import 'package:cryptick_nice_ui/modules/crypto_presenter.dart';
class HomePage extends StatefulWidget {
@override
_HomePageState createState() => new _HomePageState();
}
class _HomePageState extends State<HomePage> implements CryptoListViewContract {
CryptoListPresenter _presenter;
List<Crypto> _currencies;
bool _isLoading;
final List<MaterialColor> _colors = [Colors.blue, Colors.indigo, Colors.red];
List<String> items = [
"Item 1",
"Item 2",
"Item 3",
"Item 4",
"Item 5",
"Item 6",
"Item 7",
"Item 8"
];
_HomePageState() {
_presenter = new CryptoListPresenter(this);
}
@override
void initState() {
super.initState();
_isLoading = true;
_presenter.loadCurrencies();
}
@override
Widget build(BuildContext context) {
return new Container(
decoration: new BoxDecoration(
color: const Color(0xFF273A48),
),
child: new Stack(
children: <Widget>[
new Scaffold(
appBar: new AppBar(
title: new Text("cryp"),
elevation: 0.0,
backgroundColor: Colors.transparent,
),
backgroundColor: Colors.transparent,
body: _cryptoWidget(),
)
],
),
);
}
Widget _cryptoWidget(Crypto currency, MaterialColor color) {
final _width = MediaQuery.of(context).size.width;
final _height = MediaQuery.of(context).size.height;
final headerList = new ListView.builder(
itemBuilder: (context, index) {
EdgeInsets padding = index == 0?const EdgeInsets.only(
left: 20.0, right: 10.0, top: 4.0, bottom: 30.0):const EdgeInsets.only(
left: 10.0, right: 10.0, top: 4.0, bottom: 30.0);
_getHtmlUI();
return new Padding(
padding: padding,
);
},
scrollDirection: Axis.horizontal,
itemCount: items.length,
);
new Scaffold(
appBar: new AppBar(
title: new Text('hello'),
elevation: 0.0,
backgroundColor: Colors.transparent,
),
backgroundColor: Colors.transparent,
body: new Container(
child: new Stack(
children: <Widget>[
new Padding(
padding: new EdgeInsets.only(top: 10.0),
child: new Column(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisSize: MainAxisSize.max,
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
new Align(
alignment: Alignment.centerLeft,
child: new Padding(
padding: new EdgeInsets.only(left: 8.0),
child: new Text(
'Your Feed',
style: new TextStyle(color: Colors.white70),
)),
),
new Container(
height: 300.0, width: _width, child: headerList),
new Expanded(child:
ListView.builder(
itemBuilder:
(context, index) {
_getCryptoUI(currency, color);
}
)
)
],
),
),
],
),
),
);
return new Container(
decoration: new BoxDecoration(
color: const Color(0xFF273A48),
),
child: new Stack(
children: <Widget>[
new CustomPaint(
size: new Size(_width, _height),
painter: new Background(),
),
],
),
);
}
Container _getHtmlUI() {
return new Container(
decoration: new BoxDecoration(
borderRadius: new BorderRadius.circular(10.0),
color: Colors.lightGreen,
boxShadow: [
new BoxShadow(
color: Colors.black.withAlpha(70),
offset: const Offset(3.0, 10.0),
blurRadius: 15.0)
],
image: new DecorationImage(
image: new ExactAssetImage(
'assets/img_0.jpg'),
fit: BoxFit.fitHeight,
),
),
// height: 200.0,
width: 200.0,
child: new Stack(
children: <Widget>[
new Align(
alignment: Alignment.bottomCenter,
child: new Container(
decoration: new BoxDecoration(
color: const Color(0xFF273A48),
borderRadius: new BorderRadius.only(
bottomLeft: new Radius.circular(10.0),
bottomRight: new Radius.circular(10.0))),
height: 30.0,
child: new Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
new Text(
'hello',
style: new TextStyle(color: Colors.white),
)
],
)),
)
],
),
);
}
ListTile _getCryptoUI(Crypto currency, MaterialColor color) {
return new ListTile(
title: new Column(
children: <Widget>[
new Row(
crossAxisAlignment: CrossAxisAlignment.start,
children: <Widget>[
new Container(
height: 72.0,
width: 72.0,
decoration: new BoxDecoration(
color: Colors.lightGreen,
boxShadow: [
new BoxShadow(
color:
Colors.black.withAlpha(70),
offset: const Offset(2.0, 2.0),
blurRadius: 2.0)
],
borderRadius: new BorderRadius.all(
new Radius.circular(12.0)),
image: new DecorationImage(
image: new ExactAssetImage(
"cryptoiconsBlack/"+currency.symbol.toLowerCase()+"@2x.png",
),
fit: BoxFit.cover,
)),
),
new SizedBox(
width: 8.0,
),
new Expanded(
child: new Column(
mainAxisAlignment:
MainAxisAlignment.start,
crossAxisAlignment:
CrossAxisAlignment.start,
children: <Widget>[
new Text(
currency.name,
style: new TextStyle(
fontSize: 14.0,
color: Colors.black87,
fontWeight: FontWeight.bold),
),
_getSubtitleText(currency.price_usd, currency.percent_change_1h),
],
)),
new Icon(
Icons.shopping_cart,
color: const Color(0xFF273A48),
)
],
),
new Divider(),
],
),
);
}
Widget _getSubtitleText(String priceUSD, String percentageChange) {
TextSpan priceTextWidget = new TextSpan(
text: "\$$priceUSD\n", style: new TextStyle(color: Colors.black));
String percentageChangeText = "1 hour: $percentageChange%";
TextSpan percentageChangeTextWidget;
if (double.parse(percentageChange) > 0) {
percentageChangeTextWidget = new TextSpan(
text: percentageChangeText,
style: new TextStyle(color: Colors.green));
} else {
percentageChangeTextWidget = new TextSpan(
text: percentageChangeText, style: new TextStyle(color: Colors.red));
}
return new RichText(
text: new TextSpan(
children: [priceTextWidget, percentageChangeTextWidget]));
}
@override
void onLoadCryptoComplete(List<Crypto> items) {
// TODO: implement onLoadCryptoComplete
setState(() {
_currencies = items;
_isLoading = false;
});
}
@override
void onLoadCryptoError() {
// TODO: implement onLoadCryptoError
}
}
有关我在此应用中使用的其他文件（例如crypto_data.dart）的更多信息，请参阅this GitHub repo，我正在使用该文件为代码的某些部分建模。
答案 0 :(得分：1)
您收到错误 [dart] 2 required argument(s) expected, but 0 found. 的原因是没有传递任何参数。您提供的另一个示例：_cryptoWidget(currency, color) - 您正在尝试传递一个与所需参数不匹配的列表。
正如评论中提到的，您在这里可以做的是为 List 定义索引以获取所需的值：_cryptoWidget(_currencies[index], _colors[index])