A simple custom stream builder library based on BLOC pattern. Uses stream underneath.

Features

This allows easy adding of data from network and disposing of bloc

How To Use Custom Bloc

class Example extends StatefulWidget {
  const Example({Key? key}) : super(key: key);

  @override
  State<Example> createState() => _ExampleState();
}

class _ExampleState extends State<Example> {
  final counterBloc = CounterBloc();

  @override
  void dispose() {
    super.dispose();
    counterBloc.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: Column(
          children: [
            Expanded(
              child: CustomStreamBuilder<int, String>(
                stream: counterBloc.behaviorSubject,
                dataBuilder: (context, data) {
                  return ListView.separated(
                    itemCount: 1,
                    scrollDirection: Axis.horizontal,
                    padding:
                    const EdgeInsets.symmetric(horizontal: 4, vertical: 24),
                    itemBuilder: (context, index) {
                      return Padding(
                          padding: const EdgeInsets.symmetric(horizontal: 12),
                          child: Column(
                            crossAxisAlignment: CrossAxisAlignment.start,
                            children: [
                              Text(
                                'index: $index: data: $data',
                                style: const TextStyle(fontSize: 34),
                              ),
                            ],
                          ));
                    },
                    separatorBuilder: (context, index) {
                      return const Padding(
                        padding: EdgeInsets.symmetric(vertical: 10.0),
                        child: VerticalDivider(),
                      );
                    },
                  );
                },
                loadingBuilder: (context) => const Center(
                  child: CircularProgressIndicator(),
                ),
                errorBuilder: (context, error) => Text(
                  error,
                  style: const TextStyle(),
                ),
              ),
            ),
            const SizedBox(
              height: 34,
            ),
            Row(
              children: [
                TextButton(
                    onPressed: () {
                      counterBloc.fetchCurrent(false);
                    },
                    child: const Text(
                      'Add Value',
                      style: TextStyle(),
                    )),
                const SizedBox(
                  width: 34,
                ),
                TextButton(
                    onPressed: () {
                      counterBloc.resetData();
                    },
                    child: const Text(
                      'Set to no data',
                      style: TextStyle(),
                    )),
                const SizedBox(
                  width: 34,
                ),
                TextButton(
                    onPressed: () {
                      counterBloc.fetchCurrent(true);
                    },
                    child: const Text(
                      'Add Error',
                      style: TextStyle(),
                    )),
              ],
            ),
            const SizedBox(
              height: 34,
            )
          ],
        ),
      ),
    );
  }
}

class CounterBloc with BaseBloc<int, String> {
  int value = 0;

  CounterBloc() {
    fetchCurrent(false);
  }

  fetchCurrent(bool addError) async {
    setAsLoading();

    if (!addError) {
      await Future.delayed(const Duration(seconds: 2));
      value++;
      addToModel(value);
    } else {
      value = 0;
      addToError('Could not fetch data');
    }
  }

  resetData() {
    value = 0;
    setAsNoContent();
  }

  invalidate() {
    invalidateBaseBloc();
  }

  dispose() {
    disposeBaseBloc();
  }
}

class Example2 extends StatefulWidget {
  const Example2({Key? key}) : super(key: key);

  @override
  State<Example2> createState() => _Example2State();
}

class _Example2State extends State<Example2> {
  final counterBloc = CounterBloc();
  final newCounterBloc = CounterBloc2();

  @override
  void dispose() {
    super.dispose();
    counterBloc.dispose();
    newCounterBloc.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: Column(
          children: [
            Expanded(
              child: CustomStreamBuilder.twoSubject(
                streams: [
                  counterBloc.behaviorSubject,
                  newCounterBloc.behaviorSubject
                ],
                dataBuilder2: (context, data, secondData) {
                  var counterBlocData = data.model as int?;
                  var counterBlocState = data.itemState;
                  var counterBlocDataError = data.error as String?;
                  var newCounterBlocData = secondData.model as double?;
                  var newCounterBlocState = secondData.itemState;
                  var newCounterBlocError = secondData.error as String?;

                  return Padding(
                      padding: const EdgeInsets.symmetric(horizontal: 12),
                      child: Column(
                        crossAxisAlignment: CrossAxisAlignment.start,
                        children: [
                          if (counterBlocState == ItemState.loading)
                            const Center(
                              child: CircularProgressIndicator(),
                            )
                          else if (counterBlocState == ItemState.hasError)
                            Text(
                              'counterBlocData error: $counterBlocDataError',
                              style: const TextStyle(fontSize: 34),
                            )
                          else if (counterBlocState == ItemState.noContent)
                              const SizedBox()
                            else
                              Text(
                                'counterBlocData: $counterBlocData',
                                style: const TextStyle(fontSize: 34),
                              ),
                          const SizedBox(
                            height: 34,
                          ),
                          if (newCounterBlocState == ItemState.loading)
                            const Center(
                              child: CircularProgressIndicator(),
                            )
                          else if (newCounterBlocState == ItemState.hasError)
                            Text(
                              'newCounterBlocError error: $newCounterBlocError',
                              style: const TextStyle(fontSize: 34),
                            )
                          else if (newCounterBlocState == ItemState.noContent)
                              const SizedBox()
                            else
                              Text(
                                'newCounterBlocData: $newCounterBlocData',
                                style: const TextStyle(fontSize: 34),
                              ),
                        ],
                      ));
                },
                loadingBuilder: (context) => const Center(
                  child: CircularProgressIndicator(),
                ),
                errorBuilder: (context, error) => Text(
                  error,
                  style: const TextStyle(),
                ),
              ),
            ),
            const SizedBox(
              height: 34,
            ),
            Wrap(
              children: [
                TextButton(
                    onPressed: () {
                      counterBloc.fetchCurrent(false);
                    },
                    child: const Text(
                      'Add Value to stream 1',
                      style: TextStyle(),
                    )),
                const SizedBox(
                  width: 34,
                ),
                TextButton(
                    onPressed: () {
                      counterBloc.resetData();
                    },
                    child: const Text(
                      'Set to no data stream 1',
                      style: TextStyle(),
                    )),
                const SizedBox(
                  width: 34,
                ),
                TextButton(
                    onPressed: () {
                      counterBloc.fetchCurrent(true);
                    },
                    child: const Text(
                      'Add Error to stream 1',
                      style: TextStyle(),
                    )),
                const SizedBox(
                  width: 34,
                ),
                TextButton(
                    onPressed: () {
                      newCounterBloc.fetchCurrent(false);
                    },
                    child: const Text(
                      'Add Value to stream 2',
                      style: TextStyle(color: Colors.red),
                    )),
                const SizedBox(
                  width: 34,
                ),
                TextButton(
                    onPressed: () {
                      newCounterBloc.resetData();
                    },
                    child: const Text(
                      'Set to no data stream 2',
                      style: TextStyle(color: Colors.red),
                    )),
                const SizedBox(
                  width: 34,
                ),
                TextButton(
                    onPressed: () {
                      newCounterBloc.fetchCurrent(true);
                    },
                    child: const Text(
                      'Add Error to stream 2',
                      style: TextStyle(color: Colors.red),
                    )),
              ],
            ),
            const SizedBox(
              height: 34,
            )
          ],
        ),
      ),
    );
  }
}

class CounterBloc2 with BaseBloc<double, String> {
  double value = 0;

  CounterBloc2() {
    fetchCurrent(false);
  }

  fetchCurrent(bool addError) async {
    setAsLoading();

    if (!addError) {
      await Future.delayed(const Duration(seconds: 2));
      value += 0.5;
      addToModel(value);
    } else {
      value = 0;
      addToError('Could not fetch data');
    }
  }

  resetData() {
    value = 0;
    setAsNoContent();
  }

  invalidate() {
    invalidateBaseBloc();
  }

  dispose() {
    disposeBaseBloc();
  }
}

class ExampleMulti extends StatefulWidget {
  const ExampleMulti({Key? key}) : super(key: key);

  @override
  State<ExampleMulti> createState() => _ExampleMultiState();
}

class _ExampleMultiState extends State<ExampleMulti> {
  final counterBloc = CounterBloc();
  final newCounterBloc = CounterBloc2();

  @override
  void dispose() {
    super.dispose();
    counterBloc.dispose();
    newCounterBloc.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: SafeArea(
        child: Column(
          children: [
            Expanded(
              child: CustomStreamBuilder.multiSubject(
                streams: [
                  counterBloc.behaviorSubject,
                  newCounterBloc.behaviorSubject
                ],
                itemBuilderMulti: (context, data) {
                  var counterBlocData = data.first.model as int?;
                  var counterBlocState = data.first.itemState;
                  var counterBlocDataError = data.first.error as String?;
                  var newCounterBlocData = data.elementAt(1).model as double?;
                  var newCounterBlocState = data.elementAt(1).itemState;
                  var newCounterBlocError = data.elementAt(1).error as String?;

                  return Padding(
                      padding: const EdgeInsets.symmetric(horizontal: 12),
                      child: Column(
                        crossAxisAlignment: CrossAxisAlignment.start,
                        children: [
                          if (counterBlocState == ItemState.loading)
                            const Center(
                              child: CircularProgressIndicator(),
                            )
                          else if (counterBlocState == ItemState.hasError)
                            Text(
                              'counterBlocData error: $counterBlocDataError',
                              style: const TextStyle(fontSize: 34),
                            )
                          else if (counterBlocState == ItemState.noContent)
                              const SizedBox()
                            else
                              Text(
                                'counterBlocData: $counterBlocData',
                                style: const TextStyle(fontSize: 34),
                              ),
                          const SizedBox(
                            height: 34,
                          ),
                          if (newCounterBlocState == ItemState.loading)
                            const Center(
                              child: CircularProgressIndicator(),
                            )
                          else if (newCounterBlocState == ItemState.hasError)
                            Text(
                              'newCounterBlocError error: $newCounterBlocError',
                              style: const TextStyle(fontSize: 34),
                            )
                          else if (newCounterBlocState == ItemState.noContent)
                              const SizedBox()
                            else
                              Text(
                                'newCounterBlocData: $newCounterBlocData',
                                style: const TextStyle(fontSize: 34),
                              ),
                        ],
                      ));
                },
              ),
            ),
            const SizedBox(
              height: 34,
            ),
            Wrap(
              children: [
                TextButton(
                    onPressed: () {
                      counterBloc.fetchCurrent(false);
                    },
                    child: const Text(
                      'Add Value to stream 1',
                      style: TextStyle(),
                    )),
                const SizedBox(
                  width: 34,
                ),
                TextButton(
                    onPressed: () {
                      counterBloc.resetData();
                    },
                    child: const Text(
                      'Set to no data stream 1',
                      style: TextStyle(),
                    )),
                const SizedBox(
                  width: 34,
                ),
                TextButton(
                    onPressed: () {
                      counterBloc.fetchCurrent(true);
                    },
                    child: const Text(
                      'Add Error to stream 1',
                      style: TextStyle(),
                    )),
                const SizedBox(
                  width: 34,
                ),
                TextButton(
                    onPressed: () {
                      newCounterBloc.fetchCurrent(false);
                    },
                    child: const Text(
                      'Add Value to stream 2',
                      style: TextStyle(color: Colors.red),
                    )),
                const SizedBox(
                  width: 34,
                ),
                TextButton(
                    onPressed: () {
                      newCounterBloc.resetData();
                    },
                    child: const Text(
                      'Set to no data stream 2',
                      style: TextStyle(color: Colors.red),
                    )),
                const SizedBox(
                  width: 34,
                ),
                TextButton(
                    onPressed: () {
                      newCounterBloc.fetchCurrent(true);
                    },
                    child: const Text(
                      'Add Error to stream 2',
                      style: TextStyle(color: Colors.red),
                    )),
              ],
            ),
            const SizedBox(
              height: 34,
            )
          ],
        ),
      ),
    );
  }
}


Libraries

custom_bloc