print语句和它下面的任何语句都不会运行,错误消息会指向上面以var time
开头的最后一行.我还验证了earthquakes
是一个可增长的列表,这意味着earthquakes[0]
应该运行没有问题,但它不...我做错了什么?如果问题需要进一步澄清,请告诉我,我会提供.
我的代码中有问题的部分如下所示.第43行报告错误.
import 'package:flutter/material.dart';
import 'dart:async';
import 'dart:convert';
import 'package:http/http.dart' as http;
import 'package:intl/intl.dart';
class Quake extends StatefulWidget {
var _data;
Quake(this._data);
@override
State<StatefulWidget> createState() => new QuakeState(_data);
}
class QuakeState extends State<Quake> {
// https://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_day.geojson
// "https://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/all_day.geojson";
var _data;
QuakeState(this._data);
@override
Widget build(BuildContext context) {
// debugPrint(_data['features'].runtimeType.toString());
List earthquakes = _data['features'];
return new Scaffold(
appBar: new AppBar(
title: new Text("Quakes - USGS All Earthquakes"),
backgroundColor: Colors.red,
centerTitle: true,
),
body: new ListView.builder(
itemCount: earthquakes.length,
itemBuilder: (BuildContext context, int index) {
print("${earthquakes[index]}");
var earthquake = earthquakes[index];
var time = earthquake['properties']['time'];
time *= 1000;
//var dateTime = new DateTime.fromMillisecondsSinceEpoch(int.parse(time));
//time = new DateFormat.yMMMMd(dateTime).add_jm();
return new ListTile(
title: new Text(time ?? "Empty"),
);
}));
}
}
Future<Map> getJson(String url) async {
return await http.get(url).then((response) => json.decode(response.body));
}