Flutter - Sorting Cloud Firestore

Question

I am trying to sort the listview that is coming in. Since this listview is images, I added a number to the firestore object so I can sort ascending.

I cannot seem to get the items to sort, and I am sure its how I built the app.

I tried to add the .orderBy() to the collection, however its says Query is not a type of CollectionReference.

Here is my page

import 'package:flutter/material.dart';
import 'dart:async';
import 'package:cloud_firestore/cloud_firestore.dart';

class Events extends StatefulWidget {
  @override
  _EventsState createState() => _EventsState();
}

class _EventsState extends State<Events> {
  StreamSubscription<QuerySnapshot> subscription;

  List<DocumentSnapshot> snapshot;

  CollectionReference collectionReference =
  Firestore.instance.collection("Events");


  @override

  void initState() {
    subscription = collectionReference.snapshots().listen((datasnapshot) {
      setState(() {
        snapshot = datasnapshot.documents;
      });
    });
    super.initState();
  }

//  passData(DocumentSnapshot snap) {
//    Navigator.of(context).push(
//        MaterialPageRoute(builder: (context) => EventPage(snapshot: snap,)));
//  }

  Widget build(BuildContext context) {
    return Scaffold(
         backgroundColor: Colors.white,
      body: Column(
        children: <Widget>[
          Container(
            width: MediaQuery.of(context).size.width,
            height: 200,
            decoration: BoxDecoration(
              image: DecorationImage(
                fit: BoxFit.fill,
                image: AssetImage("assets/images/events.jpg"),
              ),
            ),
          ),
          Divider(
            color: Colors.black,
          ),
          Expanded(
            child: ListView.separated(separatorBuilder: (context, index) => Divider(color: Colors.black12,
    ), itemCount: snapshot.length,
    itemBuilder: (context, index){
              return Card(
                child: Container(
                  width: MediaQuery.of(context).size.width,
                  height: 210,
                  decoration: BoxDecoration(
                    image: DecorationImage(
                      fit: BoxFit.fill,
                      image: NetworkImage(snapshot[index].data["image"]),
                    ),
                  ),
                ),

              );
    }

          ))
        ],
      ),
    );
  }
}

I really would like to sort these images by predetermined numbers in teh database.

Daniel V. · Accepted Answer · 2019-06-01 10:45:59Z

26

I think it's just a type error you introduces by a simple oversight. (Please, next time append the error case for you app, I am guessing here.)

You have:

CollectionReference collectionReference = Firestore.instance.collection("Events");

With orderBy, you should have:

Query collectionReference = Firestore.instance.collection("Events").orderBy('field');

orderBy should returns a Query, you can no longer store it as a CollectionReference.

answered Jun 1, 2019 at 10:45

Daniel V.

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4 Comments

Robert Williams Over a year ago

How can we get last 10 events instead of getting all of them?

Faaatman Over a year ago

@RobertWilliams you can use .limit(//numberOfEvents) after ordering them.

Faaatman Over a year ago

Yeah reverse the ordering method and limit them and then reverse the list.

Fethi Over a year ago

how to order the element with "timeStamp' ?

Cuong Pham · Accepted Answer · 2021-03-29 03:09:58Z

0

To use orderBy query, you might need to create indexes for your database. Otherwise, it doesn't work. Check the log if it doesn't work, you will see the link to create indexes.

Something similar to this:

W/Firestore( 3895): string_value: "7358efd28f0211eb97f404d3b0f4ef56" order by pageName, name);limitType=LIMIT_TO_FIRST) failed: Status{code=FAILED_PRECONDITION, description=The query requires an index. You can create it here: https://console.firebase.google.com/v1/r/project/myProject/firestore/indexes?create_composite=Ckxwcm9qZWN0cy90aWVuZy12aWV0LWRlcC9kYXRhYmFzZXMvKGRlZmF1bHQpL2NvbGxlY3Rpb25Hcm91cHMvcGFnZXMvaW5kZXhlcy9fEAEaCgoGYm9va0lkEAEaDAoIcGFnZU5hbWUQARoMCghfX25hbWVfXxAB, cause=null}

answered Mar 29, 2021 at 3:09

Cuong Pham

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