Flutter: Firebase Realtime Remove object from a li

I am consulting all the clubs registered in the database. And for every club I add it to a list of objects.

When the person deletes the club deletes the club from the database, but in the list of items is not deleted, I have tried to do the following:

My NotClub-Player.dart class

// FIREBASE CLUBS
List<Club> items = List();
Club item;
DatabaseReference itemRef;

@override
void initState() {
   super.initState();
   item = Club("","","",0,"","","","",0,0,false,"","","","","",false,"","","","","","","","","","","");
   final FirebaseDatabase database = FirebaseDatabase.instance;
   itemRef = database.reference().child(player.player_game_platform).child("CLUB");
   itemRef.onChildAdded.listen(_onEntryAdded);
   itemRef.onChildRemoved.listen(_onEntryRemoved);
   itemRef.onChildChanged.listen(_onEntryChanged);
}

// CLUBS LISTENERS
_onEntryAdded(Event event) {
 setState(() {
   items.add(Club.fromSnapshot(event.snapshot));
 });
}

_onEntryRemoved(Event event) {
 setState(() {
   items.remove(Club.fromSnapshot(event.snapshot));
 });
}

_onEntryChanged(Event event) {
 var old = items.singleWhere((entry) {
   return entry.key == event.snapshot.key;
 });
 setState(() {
   items[items.indexOf(old)] = Club.fromSnapshot(event.snapshot);
 });
}

My problem: In _onEntryRemoved there is an event. In that event, it returns the item that has been deleted. But it does not delete the corresponding item from the list.

In the database, it has been successfully deleted. But the list containing the object has not deleted it.

This is my query

rnew Flexible(
            child: new FirebaseAnimatedList(
              query: FirebaseDatabase.instance.reference().child(player.player_game_platform).child("CLUB").orderByChild("club_name"),
              itemBuilder: (BuildContext context, DataSnapshot snapshot,
                  Animation<double> animation, int index) {
                return new Column(
                  children: <Widget>[
                    new Container(
                      decoration: new BoxDecoration(
                        color: Colors.grey[300],
                      ),
                      child: new ListTile(
                        leading: new CachedNetworkImage(imageUrl: items[index].club_logo, width: 60.0),
                        title: new Text(items[index].club_name, style: new TextStyle(color: Colors.black)),
                        subtitle: new Text("CAPTAIN: "+items[index].club_captain, style: new TextStyle(color: Colors.black)),
                        trailing: new RaisedButton(
                            color: Colors.lightBlue[500],
                            child: new Text("JOIN", style: new TextStyle(color: Colors.white)),
                            onPressed: (){

                            }
                        ),
                      ),
                    ),
                    new Divider(
                      color: Colors.grey[700],
                      height: 0.0,
                    ),
                  ],
                );
              },
            ),
          ),

Here what I get in the _onEntryRemoved - It returns the correct removal, But removing the list does not apply to me.

E/flutter (15214): [ERROR:topaz/lib/tonic/logging/dart_error.cc(16)] Unhandled exception:
E/flutter (15214): setState() called after dispose(): _join_clubState#a99f1(lifecycle state: defunct, not mounted)
E/flutter (15214): This error happens if you call setState() on a State object for a widget that no longer appears in the widget tree (e.g., whose parent widget no longer includes the widget in its build). This error can occur when code calls setState() from a timer or an animation callback. The preferred solution is to cancel the timer or stop listening to the animation in the dispose() callback. Another solution is to check the "mounted" property of this object before calling setState() to ensure the object is still in the tree.
E/flutter (15214): This error might indicate a memory leak if setState() is being called because another object is retaining a reference to this State object after it has been removed from the tree. To avoid memory leaks, consider breaking the reference to this object during dispose().
E/flutter (15214): #0      State.setState.<anonymous closure> (package:flutter/src/widgets/framework.dart:1098:9)
E/flutter (15214): #1      State.setState (package:flutter/src/widgets/framework.dart:1124:6)
E/flutter (15214): #2      _join_clubState._onEntryRemoved (package:proclubscommunity/Club-Player.dart:807:5)
E/flutter (15214): #3      _RootZone.runUnaryGuarded (dart:async/zone.dart:1316:10)
E/flutter (15214): #4      _BufferingStreamSubscription._sendData (dart:async/stream_impl.dart:330:11)
E/flutter (15214): #5      _DelayedData.perform (dart:async/stream_impl.dart:578:14)
E/flutter (15214): #6      _StreamImplEvents.handleNext (dart:async/stream_impl.dart:694:11)
E/flutter (15214): #7      _PendingEvents.schedule.<anonymous closure> (dart:async/stream_impl.dart:654:7)
E/flutter (15214): #8      _microtaskLoop (dart:async/schedule_microtask.dart:41:21)
E/flutter (15214): #9      _startMicrotaskLoop (dart:async/schedule_microtask.dart:50:5)
I/flutter (15214): {club_logo: url_image, club_note: , club_since: , club_three_position: , club_market: false, club_market_color: , club_six_position: , club_premium: false, club_twitter: https://www.twitter.com/, club_first_position: , club_category: 0, club_seven_position: , club_description: , club_copa: 0, club_country: ESPAÑA, club_liga: 0, club_four_position: , club_logo_file_name: club_logo.png, club_plataform: PS4, club_nine_position: , club_captain: RaiiLKilleR, club_name: Barcelona, club_five_position: , club_eight_position: , club_id: 1, club_second_position: , club_logo_folder_name: PS4_Barcelona, club_twitch: https://www.twitch.tv/, club_youtube: https://www.youtube.com/}

Adding key to the widget:

            return new Column(
              key: new ObjectKey(items[index].club_name),
              children: <Widget>[
                new Container(
                  decoration: new BoxDecoration(
                    color: Colors.grey[300],
                  ),
                  child: new ListTile(
                    leading: new CachedNetworkImage(imageUrl: items[index].club_logo, width: 60.0),
                    title: new Text(items[index].club_name, style: new TextStyle(color: Colors.black)),
                    subtitle: new Text("Captain: "+items[index].club_captain, style: new TextStyle(color: Colors.black)),
                    trailing: new RaisedButton(
                        color: Colors.lightBlue[500],
                        child: new Text("JOIN", style: new TextStyle(color: Colors.white)),
                        onPressed: (){

                        }
                    ),
                  ),
                ),
                new Divider(
                  color: Colors.grey[700],
                  height: 0.0,
                ),
              ],
            );

_onEntryRemoved()

  _onEntryRemoved(Event event) {
    setState(() {
      print(event.snapshot.value['club_name']);
      items.remove(event.snapshot.value['club_name']);
    });
  }

Your problem lies on Club.

When you create List<Club> items and later perform items.remove(clubInstance), internally the remove method will use the standard object equals method implementation, which is unaware of your key.

The same would happen if you try to use items.indexOf(clubInstance). It will never 'find' the item, always returning -1.

You can either change your implementation, iterating through the items to find out exactly which item you need to delete, and then remove it, OR you could implement == and hashCode in the Club class.

If you intend to use club_name as the key, adding these two lines will probably solve it.

class Club {
  Club({this.club_name});
  final String club_name;

  // this is what you would have to add to your class:
  bool operator ==(o) => o is Club && o.club_name == club_name;
  int get hashCode => club_name.hashCode;
}

Note: this is unrelated to flutter or firebase, this is just dart!