firebase - 如何使用Flutter从Firebase数据库查询中打印列表？

Question

我正在尝试从我的Firebase数据库中打印属性列表。当前数据库的结构如下:



我首先要在控制台上打印显示名称的列表，以便可以看到它的工作原理，然后再将其添加到ListView中。任何帮助表示赞赏!

import 'package:firebase_database/firebase_database.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';

// This is the model class
class Mod {
  final String name;
  final String nextEpisode;
  final String prevEpisode;

  Mod(this.name, this.nextEpisode, this.prevEpisode);

  Mod.fromJson(Map<String, dynamic> json)
    : name = json['name'],
      nextEpisode = json['nextEpisode'],
      prevEpisode = json['prevEpisode'];
}


// This is the screen class
class FTest2 extends StatefulWidget {
  @override
  _FTest2State createState() => _FTest2State();
}

class _FTest2State extends State<FTest2> {

  List<Mod> list = List();

  MakeCall() {
    final mainReference = FirebaseDatabase.instance.reference();
    mainReference.child('-M5Uol7Xldnc8wvNXnNg').once().then((DataSnapshot dataSnapshot){
      this.setState(() {
        for(var value in dataSnapshot.value){
          list.add(Mod.fromJson(value));
        }
      });
    });
    print(list);
  }

  void getData() {
    MakeCall();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(title: Text('This is App Bar for the FB Test')),
        body: Column(
          children: <Widget>[
            RaisedButton(
              child: Text('Press for data'),
              onPressed: () {
                getData();
              },
            ),
          ],
        ));
  }
}

Answer 1

您正在遍历一个特定节目的节点，这意味着value实际上是该节目下的子属性之一:name，nextEpisode和prevEpisode。您可能正在寻找的是听所有节目的onChildAdded，然后为每个节目获取name属性:

mainReference.child('shows')
  .onChildAdded
  .forEach((event) => {
    print(event.snapshot.key+": "+event.snapshot.value.toString());
    this.setState(() {
      list.add(Mod.fromJson(event.snapshot.value["name"]));
    });
  });

另请参见几周前的答复表: Flutter: Firebase Real-Time database orderByChild has no impact on query result