我正在尝试建立一个列表视图，以显示与他们各自的用户有关的一些事件，但是列表是在方法完成之前构建的，然后导致一个空列表...
我尝试过，但是问题仍然存在：
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:project/Methods.dart';
import 'package:project/Views/CadastroUsuario.dart';
import 'package:project/classes/eventos.dart';
class ListagemEventos extends StatefulWidget {
@override
ListagemEventosState createState() => new ListagemEventosState();
}
class ListagemEventosState extends State<ListagemEventos> {
@override
void initState() {
super.initState();
}
Future<List<Event>> getEvents() async {
CollectionReference eventsDoc = Firestore.instance.collection("events");
return await eventsDoc.getDocuments().then((snapshot) {
List<Event> events = new List<Event>();
snapshot.documents.forEach((doc) async {
Event event = new Event();
String id;
event.description = doc["description"];
event.city = doc["city"];
event.state = doc["state"];
event.location = doc["location"];
event.date = doc["date"];
event.placesAvailable = doc["placesAvailable"];
event.totalPlaces = doc["placesTotal"];
id = doc["userId"];
event.owner = new UserOwner();
CollectionReference eventsDoc = Firestore.instance.collection("users");
event.owner = await eventsDoc.document(id).get().then((doc) {
UserOwner userOwner = new UserOwner();
userOwner.userid = id;
userOwner.name = doc["name"];
userOwner.phone = doc["phone"];
userOwner.email = doc["email"];
userOwner.city = doc["city"];
userOwner.state = doc["state"];
userOwner.photo = doc["photo"];
event.owner = userOwner;
return userOwner;
});
events.add(event);
});
return events;
});
}
Widget createListView(BuildContext context, AsyncSnapshot snapshot) {
List<Event> events = snapshot.data;
return new ListView.builder(
itemCount: events.length,
itemBuilder: (BuildContext context, int index){
return item(events[index]);
},
);
}
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text('Eventos'),
),
body: new FutureBuilder(
future: getEvents(),
builder: (BuildContext context, AsyncSnapshot snapshot){
switch (snapshot.connectionState) {
case ConnectionState.waiting: return new Text("Loading...");
default:
if(snapshot.hasError)
return new Text("Erro: ${snapshot.error}");
else
return createListView(context, snapshot);
}
},
),
floatingActionButton: new FloatingActionButton(
tooltip: 'Novo',
child: new Icon(Icons.add),
onPressed: () async {
Navigation navigation = new Navigation();
navigation.navigaTo(context, CadastroUsuario());
},
),
);
}
Widget item(Event event) {
return new Card(
elevation: 4.0,
child: new Column(
children: <Widget>[
new Row(
children: <Widget>[
new Column(
children: <Widget>[
new Text(event.owner.name.toString(),
style: TextStyle(fontSize: 20.0),
overflow: TextOverflow.ellipsis,),
],
),
new Column(
children: <Widget>[
],
)
],
),
new Container(
color: Colors.blue,
height: 150.0,
),
new Row(
children: <Widget>[
new Row(
children: <Widget>[
new Text(event.description.toString(),
style: TextStyle(fontSize: 20.0),
overflow: TextOverflow.ellipsis,),
],
),
new Row(
children: <Widget>[
new Text(event.location.toString(),
style: TextStyle(color: Colors.grey[350]),
overflow: TextOverflow.ellipsis,),
],
),
new Row(
children: <Widget>[
new Text(event.city.toString() +' - '+ event.state.toString(),
style: TextStyle(color: Colors.grey[350]),
overflow: TextOverflow.ellipsis,),
],
)
]
)
],
)
);
}
}
我该如何解决？
有其他方法可以做到吗？
PS：如果您能给我一个例子，我将不胜感激
答案 0 :(得分：1)
由于我的代码还具有其他依赖性，因此我无法运行您的代码，因此，我将在不进行测试的情况下尽力帮助您。
关于颤动要记住的一件事（这使我更容易理解），除非调用此方法，否则视图永远不会刷新。
this.setState(() {});
因此，当您100％确定数据已加载时，请调用该函数。那将重建您的视图并再次调用build函数，这将刷新您的视图。希望对您有帮助。
知道了这一点，您可以使代码更加容易。您可以简单地创建一个变量，其子视图为子视图。将该变量填充到异步函数中，然后再次调用setState。这将填充列表视图。
答案 1 :(得分：0)
最后我找到了办法...
我正在initState中初始化一个侦听器，当我的Firestore发生更改时，我使用setState来重建我的普通列表视图
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:project/Methods.dart';
import 'package:project/Views/CadastroUsuario.dart';
import 'package:project/classes/eventos.dart';
class ListagemEventos extends StatefulWidget {
@override
ListagemEventosState createState() => new ListagemEventosState();
}
class ListagemEventosState extends State<ListagemEventos> {
List<Event> _events;
@override
void initState() {
super.initState();
_events = new List<Event>();
Firestore.instance.collection("events").snapshots().listen((snapshot){
getEvents(snapshot);
});
}
void getEvents(QuerySnapshot eventsDoc) {
List<Event> events = new List<Event>();
eventsDoc.documents.forEach((doc) async {
Event event = new Event();
String id;
event.description = doc["description"];
event.city = doc["city"];
event.state = doc["state"];
event.location = doc["location"];
event.date = doc["date"];
event.placesAvailable = doc["placesAvailable"];
event.totalPlaces = doc["placesTotal"];
id = doc["userId"];
event.owner = new UserOwner();
CollectionReference eventsDoc = Firestore.instance.collection("users");
event.owner = await eventsDoc.document(id).get().then((doc) {
UserOwner userOwner = new UserOwner();
userOwner.userid = id;
userOwner.name = doc["name"];
userOwner.phone = doc["phone"];
userOwner.email = doc["email"];
userOwner.city = doc["city"];
userOwner.state = doc["state"];
userOwner.photo = doc["photo"];
event.owner = userOwner;
return userOwner;
});
events.add(event);
setState(() {
_events = events;
});
});
}
@override
Widget build(BuildContext context) {
return new Scaffold(
appBar: new AppBar(
title: new Text('Eventos'),
),
body:
_events.length == 0
?
new Center(child: new CircularProgressIndicator())
:
new ListView.builder(
itemCount: _events.length,
itemBuilder: (BuildContext context, int index){
return item(_events[index]);
}
)
,floatingActionButton: new FloatingActionButton(
tooltip: 'Novo',
child: new Icon(Icons.add),
onPressed: () async {
Navigation navigation = new Navigation();
navigation.navigaTo(context, CadastroUsuario());
},
),
);
}
Widget item(Event event) {
return new Card(
elevation: 4.0,
child: new Column(
children: <Widget>[
new Row(
children: <Widget>[
new Column(
children: <Widget>[
new Text(event.owner.name.toString(),
style: TextStyle(fontSize: 20.0),
overflow: TextOverflow.ellipsis,),
],
),
new Column(
children: <Widget>[
],
)
],
),
new Container(
color: Colors.blue,
height: 150.0,
),
new Row(
children: <Widget>[
new Row(
children: <Widget>[
new Text(event.description.toString(),
style: TextStyle(fontSize: 20.0),
overflow: TextOverflow.ellipsis,),
],
),
new Row(
children: <Widget>[
new Text(event.location.toString(),
style: TextStyle(color: Colors.grey[350]),
overflow: TextOverflow.ellipsis,),
],
),
new Row(
children: <Widget>[
new Text(event.city.toString() +' - '+ event.state.toString(),
style: TextStyle(color: Colors.grey[350]),
overflow: TextOverflow.ellipsis,),
],
)
]
)
],
)
);
}
}