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[英]I'm getting a "1 positional argument(s) expected, but 0 found." error in Flutter using Dart with Cloud Firestore?
[英]Error: “1 positional argument(s) expected, but 0 found” flutter dart error
我正在尝试使用一些图表构建一个应用程序,我从这个示例开始,但它没有启动应用程序的第一部分,所以我尝试添加:
void main() {
runApp(SimpleTimeSeriesChart());
}
但我明白了
应有 1 个位置参数,但找到了 0 个。 尝试添加缺少的 arguments。
在第二行。 我不知道我做错了什么。 谁能帮我解释我做错了什么以及解决方案是什么? 信息很清楚,但我不知道我需要添加哪个参数。 另外,任何人都可以向我指出有关此特定问题的一些文档吗? 谢谢!
import 'package:flutter/material.dart'; import 'package:charts_flutter/flutter.dart' as charts; void main() { runApp(SimpleTimeSeriesChart()); } class SimpleTimeSeriesChart extends StatelessWidget { final List < charts.Series > seriesList; final bool animate; SimpleTimeSeriesChart(this.seriesList, { this.animate }); /// Creates a [TimeSeriesChart] with sample data and no transition. factory SimpleTimeSeriesChart.withSampleData() { return new SimpleTimeSeriesChart( _createSampleData(), // Disable animations for image tests. animate: false, ); } @override Widget build(BuildContext context) { return new charts.TimeSeriesChart( seriesList, animate: animate, // Optionally pass in a [DateTimeFactory] used by the chart. The factory // should create the same type of [DateTime] as the data provided. If none // specified, the default creates local date time. dateTimeFactory: const charts.LocalDateTimeFactory(), ); } /// Create one series with sample hard coded data. static List < charts.Series < TimeSeriesSales, DateTime >> _createSampleData() { final data = [ new TimeSeriesSales(new DateTime(2017, 9, 19), 5), new TimeSeriesSales(new DateTime(2017, 9, 26), 25), new TimeSeriesSales(new DateTime(2017, 10, 3), 100), new TimeSeriesSales(new DateTime(2017, 10, 10), 75), ]; return [ new charts.Series < TimeSeriesSales, DateTime > ( id: 'Sales', colorFn: (_, __) => charts.MaterialPalette.blue.shadeDefault, domainFn: (TimeSeriesSales sales, _) => sales.time, measureFn: (TimeSeriesSales sales, _) => sales.sales, data: data, ) ]; } } /// Sample time series data type. class TimeSeriesSales { final DateTime time; final int sales; TimeSeriesSales(this.time, this.sales); }
SimpleTimeSeriesChart(this.seriesList
void main() {
runApp(SimpleTimeSeriesChart([]));
}
您可以在此处阅读有关 Dart 参数的更多信息
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