保存从 Firestore 集合中的 JSON URL 获取的列表

Question

我的小应用程序，正在从 JSON 链接获取用户列表，然后将其存储在列表中，我想将此列表放入 usersCollectionfirestore 的集合参考

我的代码

import 'dart:convert';

import 'package:flutter/material.dart';
import 'package:fluttertoast/fluttertoast.dart';
import 'dart:async';
import 'package:http/http.dart' as http;
import 'package:yat_flutter_app/main.dart';
import 'usersList.dart';
import 'package:cloud_firestore/cloud_firestore.dart';

class MyApp extends StatefulWidget {

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

class _MyAppState extends State<MyApp> {

  CollectionReference usersCollection =
  FirebaseFirestore.instance.collection('users');

  Future<List<User>> getUsers() async {
    var data = await http
        .get("https://www.json-generator.com/api/json/get/bYKKPeXRcO?indent=2");
    var jasonData = json.decode(data.body);
    List<User> users = [];

    for (var i in jasonData) {
      User user = User(i["index"], i["about"], i["name"], i["picture"],
          i["company"], i["email"]);
      users.add(user);
    }

    return users;
  }


  @override
  Widget build(BuildContext context) {

    List<User> usersList = getUsers() as List<User>;


    return Container(

      child: Column(
        children: [
          FutureBuilder(
            future: getUsers(),
            builder: (BuildContext context, AsyncSnapshot asyncSnapshop) {
              if (asyncSnapshop.hasData) {
                return Expanded(
                  child: ListView.builder(
                      shrinkWrap: true,
                      itemCount: asyncSnapshop.data.length,
                      itemBuilder: (BuildContext context, int index) {
                        return Card(
                          elevation: 5,
                          color: Colors.cyan[50],
                          child: ListTile(
                            trailing: Icon(Icons.share),
                            title: Text(asyncSnapshop.data[index].name, style: TextStyle(fontFamily: 'Tahoma',fontSize: 20,fontWeight: FontWeight.bold),),
                            leading: CircleAvatar(
                              backgroundImage: NetworkImage(
                                  asyncSnapshop.data[index].picture +
                                      asyncSnapshop.data[index].index.toString() +
                                      ".jpg"),
                            ),
                            subtitle: Text(asyncSnapshop.data[index].email,style: TextStyle(fontFamily: 'Tahmoma',fontSize: 18),),
                            onTap: (){
                              Navigator.push(context, new MaterialPageRoute(builder: (context)=>
                                  detailsPage(asyncSnapshop.data[index])
                              ));
                            },

                            onLongPress: ()=>

                                Fluttertoast.showToast(
                                    msg: asyncSnapshop.data[index].name,
                                    toastLength: Toast.LENGTH_SHORT,
                                    gravity: ToastGravity.CENTER,
                                    timeInSecForIosWeb: 1,
                                    backgroundColor: Colors.green[900],
                                    textColor: Colors.white,
                                    fontSize: 16.0
                                ),

                          ),
                        );
                      }),
                );
              } else {
                return Text("Loading, please wait...");
              }
            },
          ),

          ElevatedButton(
              child: Text('Save data'),
              onPressed: () => {
                
      usersCollection.add(getUsers()); // here's I am trying to add the result of getUsers into usersCollection 

              }),
        ],

      ),
    );
  }
}

Answer 1

Firebase 实时数据库和 Firestore 不是 SQL 数据库，数据将存储在父子关系或树结构中。

为了存储数据列表，您可以将列表转换为地图 地图可以如下初始化

Map<String, String> toMap() {
  return {
    'Fruit': "Mango",
    'Flower': "Lotus",
    'Vegetable': "Potato",
  };
}

拥有 Map 后，您可以为 firestore 设置值。您可以使用以下代码设置值

Map<String, Object> city = new Map<>();
//Loop through your list and load Map (City) values
db.collection("cities").document("LA").set(city)
.addOnSuccessListener(new OnSuccessListener<Void>() {
    @Override
    public void onSuccess(Void aVoid) {
    Log.d(TAG, "DocumentSnapshot successfully written!");
    }
}).addOnFailureListener(new OnFailureListener() {
    @Override
    public void onFailure(@NonNull Exception e) {
    Log.w(TAG, "Error writing document", e);
    }
});

您可以使用此将项目列表转换为地图

Java: How to convert List to Map

Answer 2

要将此列表推送到 Firestore，您需要在模型类中使用 fromJson 和 toJson 方法

 factory User.fromJson(Map<String, dynamic> data){
    return User(
        index: data['index'] as int,
        about: data['about'] as String,
        name: data['name'] as String,
        picture: data['picture'] as String,
        company: data['company'] as String,
        email: data['email'] as String );
  }

  Map<String, dynamic> toJson(){

    return {
        "index": index,
        "about" : about,
        "name" : name,
        "picture" : picture,
        "company" : company,
        "email" : email,
    };
  }

我建议使用json_serializable 库

那么你需要像这样对你未来的方法做一些改变

getUsers().then((users) {
// add users to map
});

然后您可以使用 fromJson 方法将其推送到 firestore 数据库

Answer 3

要将对象推送到 Firestore，您需要将 object 转换为 map。
您可以将此功能添加到您的课程中：

  Map<String, dynamic> toMap() {
    return {
      'field1': value1,
      'field2': value1,
    };
  }

要推送一个 List ，你需要将所有对象转换为 map ，你可以使用以下方法：

  static List<Map> ConvertToMap({List myList }) {
    List<Map> steps = [];
    myList.forEach((var value) {
      Map step = value.toMap();
      steps.add(step);
    });
    return steps;
  }

或者简单地说，见 how to convert List to Map

希望对你有用