[对不起我的英语不好]
在这个项目中，我正在查看来自JSON API的某些页面中的事件列表，在 CloudEvents页面中，我正在查看来自Firebase Database的另一个列表，使用事件模型......
现在，当我运行CloudEvents页面时，我得到 null
itemsEvent[i].startDate出现此错误：
A non-null String must be provided to a Text widget.我将此方法用于我的模型
这是我的事件模型
class Event {
String key;
String sectionID;
String sectionTitle;
String title;
String startDate;
String endDate;
String startDateAr;
String endDateAr;
String city;
String detail;
String location;
String more;
String link;
// for generalevent.json
String eventDate;
String eventDateAr;
Event(
{this.sectionID,
this.sectionTitle,
this.title,
this.startDate,
this.endDate,
this.startDateAr,
this.endDateAr,
this.city,
this.detail,
this.location,
this.more,
this.link,
this.eventDate,
this.eventDateAr});
factory Event.fromJson(Map<String, dynamic> json) {
return Event(
sectionID: json['section-id'],
sectionTitle: json['section-title'],
title: json['title'],
startDate: json['start-event-date'],
endDate: json['end-event-date'],
startDateAr: json['start-event-date-ar'],
endDateAr: json['end-event-date-ar'],
city: json['city'],
detail: json['detail'],
location: json['location'],
more: json['more'],
link: json['link'],
// for generalevent.json
eventDate: json['event-date'],
eventDateAr: json['event-date-ar'],
);
}
Event.fromSnapshot(DataSnapshot snapshot)
: key = snapshot.key,
title = snapshot.value['title'],
startDate = snapshot.value['startDate'];
toJson() {
return {
"title": title,
"startDate": startDate,
};
}
}
这是我的CloudEvents页面
import 'package:events/UI/styleguide.dart';
import 'package:events/models/event.dart' as e;
import 'package:events/pages/account.dart';
import 'package:firebase_auth/firebase_auth.dart';
import 'package:firebase_database/firebase_database.dart';
import 'package:firebase_database/ui/firebase_animated_list.dart';
import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'package:intl/intl.dart' as intl;
final FirebaseAuth mAuth = FirebaseAuth.instance;
final db = FirebaseDatabase.instance.reference();
FirebaseUser mCurrentUser;
List<e.Event> itemsEvent = List();
e.Event itemEvent;
DatabaseReference dbEvent;
class CloudEvents extends StatefulWidget {
final GlobalKey<ScaffoldState> scaffoldKey;
const CloudEvents({Key key, @required this.scaffoldKey}) : super(key: key);
@override
_CloudEventsState createState() => _CloudEventsState();
}
class _CloudEventsState extends State<CloudEvents> {
ScrollController _hideButtonController;
var _isVisible;
@override
initState() {
super.initState();
...
itemEvent = e.Event();
final FirebaseDatabase database = FirebaseDatabase.instance;
dbEvent = database.reference().child('events');
dbEvent.onChildAdded.listen(_onEntryAddedEvent);
dbEvent.onChildChanged.listen(_onEntryChangedEvent);
...
}
_onEntryAddedEvent(Event event) {
setState(() {
itemsEvent.add(e.Event.fromSnapshot(event.snapshot));
});
}
_onEntryChangedEvent(Event event) {
var old = itemsEvent.singleWhere((entry) {
return entry.key == event.snapshot.key;
});
setState(() {
itemsEvent[e.Event.indexOf(old)] = e.Event.fromSnapshot(event.snapshot);
});
}
@override
Widget build(BuildContext context) {
return showEvents();
}
Widget showEvents(BuildContext context) {
return Container(
height: MediaQuery.of(context).size.height,
child: Stack(
children: <Widget>[
FirebaseAnimatedList(
query: dbEvent.child(mCurrentUser.uid),
itemBuilder: (_, DataSnapshot snapshot,
Animation<double> animation, int i) {
return new ListTile(
title: new Text(snapshot.value['title']), //snapshot works well
subtitle: new Text(itemsEvent[i].startDate), // this returns null
);
}),
...
],
),
);
}
...
}