我如何从firebase中检索数据，而无需刷新

Question

我在Firebase实时数据库中具有布尔值，我需要一个更新的值，而无需屏幕刷新。 我希望它可以在颤抖上进行更新

Answer 1

处理您的问题的一种简单方法是使用“ Cloud_firestore”软件包。
我将在下面制作UA示例代码。

注意：使用Firestore之前，您必须首先确保您已经初始化了Flutterfire！请点击此链接： https://firebase.flutter.flutter.docs.docs.docs/docs/overview/overveive/view/view/view/#初始化flutterfire

import 'package:flutter/material.dart';


class TestWidget extends StatefulWidget {
  const TestWidget({Key? key}) : super(key: key);

  @override
  _TestWidgetState createState() => _TestWidgetState();
}

class _TestWidgetState extends State<TestWidget> {
  final Stream<QuerySnapshot> _usersStream =
      Firebas`eFirestore.instance.collection('your collection name in database here').snapshots();`

  @override
  Widget build(BuildContext context) {
    return StreamBuilder<QuerySnapshot>(
      stream: _usersStream,
      builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
        if (snapshot.hasError) {
          return const Text('Something went wrong');
        }

    if (snapshot.connectionState == ConnectionState.waiting) {
      return const LinearProgressIndicator();
    }


//this way you can extract your data from DB

//Of course it totally depend on if your data in Db is nested or not. just adjust it with your needs
    return ListView(
      children: snapshot.data!.docs.map((DocumentSnapshot document) {
        Map<String, dynamic> data =
            document.data()! as Map<String, dynamic>;
        return Column(children: [
          PassDataToAnotherWidget(data),
        ]);
      }).toList(),
    );
  },
);
  }
}

Answer 2

如果您在firebase实时数据库中有数据，则可以通过其 onvalue stream 。您可以使用streamBuilder：

@override
Widget build(BuildContext context) {
  var ref = FirebaseDatabase.instance.ref('path_to_value');
  return Scaffold(
    StreamBuilder(
      stream: ref.onValue,
      builder: (context, snapshot) {
        if (snapshot.hasData) return Text(snapshot.data!.snapshot.value);
        if (!snapshot.hasData) return CircularProgressIndicator();
        if (snapshot.hasError) return Text(snapshot.error);
      }
    )
  )

我建议观看此出色的Code-Along视频： firebase实时数据库和扑朔迷离-Firecasts