Flutter setState导致无限循环

Question

我是 Flutter 的新手，我想从 Firebase 获取一次数据，但是当我在 setState 中使用 foreach 时，它会出现无限循环。我试过 initState 但我无法用 Future 弄明白。

这是我的代码：

class _AnasayfaScreenState extends State<AnasayfaScreen> {
   final databaseRef = FirebaseDatabase.instance.reference();
   ActivityModel activity = ActivityModel();
   List<Map<dynamic, dynamic>> lists = [];
 }

Future getActivity() async {
return await databaseRef
    .child('activities')
    .limitToLast(3)
    .once()
    .then((DataSnapshot dataSnapshot) {
  setState(() {
    Map<dynamic, dynamic> values = dataSnapshot.value;
    lists.clear();
    values.forEach((key, values) {
      lists.add(values);
    });
  });
});
}
@override
Widget build(BuildContext context) {
getActivity();
return Scaffold(
    appBar: AppBar(
    // some stuff
  title: Text("Title: " +lists[index]["title"] +"\nDate: " + lists[index]["date"] +"\nN:  Number of people"+lists[index]["maxPeople"] + "\nActivity Owner: " +lists[index]["ownername"]),

任何帮助对我来说都是很棒的，谢谢。

Answer 1

这是您可以执行的操作的一个非常基本的示例：


class _AnasayfaScreenState extends State<AnasayfaScreen> {
   final databaseRef = FirebaseDatabase.instance.reference();
   ActivityModel activity = ActivityModel();
  bool isLoading = true;
  List<Map<dynamic, dynamic>> lists = [];
  
  @override
  void initState(){
    super.initState();
    getActivity();
  }
  
  Future getActivity() async {
    await databaseRef
    .child('activities')
    .limitToLast(3)
    .once()
    .then((DataSnapshot dataSnapshot) {
    Map<dynamic, dynamic> values = dataSnapshot.value;
    lists.clear();
    values.forEach((key, values) {
      lists.add(values);
        });
      });
    setState(() {
      isLoading = false;
    });
  }


  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: isLoading ? Container() // Add your widget and work here instead of Container
            : CircularProgressIndicator(),
    );  
  }

Flutter setState导致无限循环

Flutter setState causes infinite loop

dart

firebase

firebase-realtime-database

flutter