Flutter State Restoration of ListView or BLoC

Question

I'm trying to restore my listview widget after android kills my app from memory by using RootRestorationScope:

runApp(RootRestorationScope(
     child: MaterialApp(home: MyApp()),
     restorationId: "root",
  ));

and making my own restorable widget using extends RestorableValue:

class RestorableListBloc extends RestorableValue {
  @override
  ListBloc createDefaultValue() {
    return ListBloc(
      repository: Repository(),
    )..add(
        Fetch(),
      );
  }

  @override
  void didUpdateValue(ListBloc oldValue) {
    if (oldValue.state != value.state) {
      notifyListeners();
    }
  }

  @override
  ListBloc fromPrimitives(Object data) {
    print('data: ' + data);
    return ListBloc(repository: data);
  }

  @override
  Object toPrimitives() {
    return value.repository;
  }
}

Where ListBloc is a Bloc that controls what's in my listview widget (collection of timers right now in case anyone's curious).

I extend the class with the restoration mixing and call the bloc inside of a multibloc providers widget as follows:

class _MyAppState extends State with RestorationMixin {
  SpeedDialGenerator speedDial = SpeedDialGenerator();
  RestorableListBloc _test = RestorableListBloc();
  final assetsAudioPlayer = AssetsAudioPlayer();

  @override
  Widget build(BuildContext context) {
    return BlocProvider(
      create: (BuildContext context) => DrawerCubit(value: false),
      child: Scaffold(
        backgroundColor: Colors.blue[50],
        drawer: SafeArea(
          child: AppDrawer(),
        ),
        appBar: AppBar(
          backgroundColor: Colors.blue[900],
          title: Text('Myapp'),
          centerTitle: true,
          actions: [
            IconButton(
              icon: Image.asset('assets/images/myapp_white.png'),
              onPressed: () {},
            ),
          ],
        ),
        body: Stack(children: [
          HourglassBackground(),
          MultiBlocProvider(
              providers: [
                BlocProvider(
                  create: (context) => _test.value,
                ),
                BlocProvider(
                  create: (context) => AppStateCubit(),
                )
              ],
              child: BlocBuilder(
                builder: (context, state) {
                  if (state is Failure) {
                    return Center(
                      child: Text('Oops something went wrong!'),
                    );
                  }
                  if (state is Loaded) {
                    return Stack(children: [
                      HomePage(state: state, displayNotification: () => {}),
                      Padding(
                        padding: EdgeInsets.fromLTRB(0, 0, 10, 10),
                        child: BlocProvider(
                            create: (context) => TimerpopupCubit(),
                            child: speedDial.buildSpeedDial(context)),
                      ),
                    ]);
                  }
                  return Center(
                    child: CircularProgressIndicator(),
                  );
                },
              )),
        ]),
      ),
    );
  }

  @override
  String get restorationId => 'root';

  @override
  void restoreState(RestorationBucket oldBucket, bool initialRestore) {
    registerForRestoration(_test, restorationId);
  }

Unfortunately, everytime I run the app I get:

The following assertion was thrown building Builder:
'package:flutter/src/services/restoration.dart': Failed assertion: line 592 pos 12: 'debugIsSerializableForRestoration(value)': is not true.

There's not much documentation and I know this is a relatively new feature of flutter, but from what I gather this means that you can't currently restore a BLoC?

Is there a way around this or some other approach I should look at?

Thanks

Flutter State Restoration of ListView or BLoC

0 Answers