I am using the Fortune Wheel in this link. When I fling the wheel, it will spin and end but when it is done, I'm unable to fetch the value of the selection.
Here's what I have tried:
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter_fortune_wheel/flutter_fortune_wheel.dart';
class SpinawheelWidget extends StatefulWidget {
#override
State<StatefulWidget> createState() => SpinawheelState();
}
class SpinawheelState extends State<SpinawheelWidget> {
StreamController<int> selected = StreamController<int>();
#override
void initState() {
super.initState();
}
#override
void dispose() {
selected.close();
super.dispose();
}
#override
Widget build(BuildContext context) {
final items = <String>[
'item1',
'item2',
'item3',
'item4',
'item5',
'item6',
];
return Column(
children: [
Expanded(
child: FortuneWheel(
physics: CircularPanPhysics(
duration: Duration(seconds: 1),
curve: Curves.decelerate,
),
onFling: () {
print('onFling');
selected.add(1);
},
onAnimationStart: () {
print('animation start');
},
onAnimationEnd: () {
print('animation end ${selected.stream}');
},
animateFirst: false,
selected: selected.stream,
items: [
for (var it in items) FortuneItem(child: Text(it)),
],
),
),
],
);
}
}
The print on onAnimationEnd only shows: animation end Instance of '_ControllerStream' but not the value. I am expect to get at least one of the item or the position of the item. Please help. Thanks!
Got it to work. Just need some changes.
Change your declaration of stream controller to broadcast
StreamController<int> _controller = StreamController.broadcast();
Then the trick. In some place of your widget tree (mine was just above the FortuneWheel in a Column) insert this StreamBuilder. This will show nothing, just handle some functions. In order to let us handle the snapshot result, we wil add the _text funciontion returning a widget. See bellow:
StreamBuilder(
stream: _controller.stream,
builder: (context, snapshot) => snapshot.hasData
? _text(snapshot)
: Container(),
)
And now, the function returning the widget _text.
Widget _text(var snapshot) {
//here you cand get and handle the result and do whathever.
print(snapshot.data);
int val = snapshot.data;
print(items[val]);
return Text(snapshot.data.toString()); //you dont need to return //anything here. Just replace the Text widget with SizedBox() to return //nothing.
}
As, the library is using Stream you will need to use stream method to get data from selection.One such method is called listen()
Rest you can check this : Medium Link - Streams In Flutter
var rendomval = Fortune.randomInt(0, items.length); setState(() { selected.add(rendomval); }); print(rendomval);
Declare the stream controller like this
StreamController<int> _controller = StreamController.broadcast();
then call the listen whatever you want , suggesting use listener inside initState function
_controller.stream.listen((value) {
print('Value from controller: $value');
})
Related
I am getting this error when I have signed out from my flutter app and trying to log in again:
StateError (Bad state: Stream has already been listened to.)
The code that gives me this error is on my first page:
#override
void initState() {
AwesomeNotifications().actionStream.listen((notification) async {
if (notification.channelKey == 'scheduled_channel') {
var payload = notification.payload['payload'];
var value = await FirebaseFirestore.instance
.collection(widget.user.uid)
.doc(payload)
.get();
navigatorKey.currentState.push(PageRouteBuilder(
pageBuilder: (_, __, ___) => DetailPage(
user: widget.user,
i: 0,
docname: payload,
color: value.data()['color'].toString(),
createdDate: int.parse((value.data()['date'].toString())),
documentId: value.data()['documentId'].toString(),)));
}
});
super.initState();
}
And on another page that contains the sign out code.
await FirebaseAuth.instance.signOut();
if (!mounted) return;
Navigator.pushNamedAndRemoveUntil(context,
"/login", (Route<dynamic> route) => false);
What can I do to solve this? Is it possible to stop listen to actionstream when I log out? Or should I do it in another way?
Streams over all are single use, they replace the callback hell that that ui is, at first a single use streams can seem useless but that may be for a lack of foresight. Over all (at lest for me) flutter provides all the necessary widgets to not get messy with streams, you can find them in the Implementers section of ChangeNotifier and all of those implement others like TextEditingController.
With that, an ideal (again, at least for me) is to treat widgets as clusters where streams just tie them in a use case, for example, the widget StreamBuilder is designed to build on demand so it only needs something that pumps changes to make a "live object" like in a clock, a periodic function adds a new value to the stream and the widget just needs to listen and update.
To fix your problem you can make .actionStream fit the case you are using it or change a bit how are you using it (having a monkey patch is not good but you decide if it is worth it).
This example is not exactly a "this is what is wrong, fix it", it is more to showcase a use of how pushNamedAndRemoveUntil and StreamSubscription can get implemented. I also used a InheritedWidget just because is so useful in this cases. One thing you should check a bit more is that the variable count does not stop incrementing when route_a is not in focus, the stream is independent and it will be alive as long as the widget is, which in your case, rebuilding the listening widget is the error.
import 'dart:async';
import 'package:flutter/material.dart';
void main() => runApp(App());
const String route_a = '/route_a';
const String route_b = '/route_b';
const String route_c = '/route_c';
class App extends StatelessWidget {
Stream<int> gen_nums() async* {
while (true) {
await Future.delayed(Duration(seconds: 1));
yield 1;
}
}
#override
Widget build(BuildContext ctx) {
return ReachableData(
child: MaterialApp(
initialRoute: route_a,
routes: <String, WidgetBuilder>{
route_a: (_) => Something(stream: gen_nums()),
route_b: (_) => FillerRoute(),
route_c: (_) => SetMount(),
},
),
);
}
}
class ReachableData extends InheritedWidget {
final data = ReachableDataState();
ReachableData({super.key, required super.child});
static ReachableData of(BuildContext ctx) {
final result = ctx.dependOnInheritedWidgetOfExactType<ReachableData>();
assert(result != null, 'Context error');
return result!;
}
#override
bool updateShouldNotify(ReachableData old) => false;
}
class ReachableDataState {
String? mount;
}
// route a
class Something extends StatefulWidget {
// If this widget needs to be disposed then use the other
// constructor and this call in the routes:
// Something(subscription: gen_nums().listen(null)),
// final StreamSubscription<int> subscription;
// Something({required this.subscription, super.key});
final Stream<int> stream;
Something({required this.stream, super.key});
#override
State<Something> createState() => _Something();
}
class _Something extends State<Something> {
int count = 0;
void increment_by(int i) => setState(
() => count += i,
);
#override
void initState() {
super.initState();
widget.stream.listen(increment_by);
// To avoid any funny errors you should set the subscription
// on pause or the callback to null on dispose
// widget.subscription.onData(increment_by);
}
#override
Widget build(BuildContext ctx) {
var mount = ReachableData.of(ctx).data.mount ?? 'No mount';
return Scaffold(
body: InkWell(
child: Text('[$count] Push Other / $mount'),
onTap: () {
ReachableData.of(ctx).data.mount = null;
Navigator.of(ctx).pushNamed(route_b);
},
),
);
}
}
// route b
class FillerRoute extends StatelessWidget {
const FillerRoute({super.key});
#override
Widget build(BuildContext ctx) {
return Scaffold(
body: InkWell(
child: Text('Go next'),
// Option 1: go to the next route
// onTap: () => Navigator.of(ctx).pushNamed(route_c),
// Option 2: go to the next route and extend the pop
onTap: () => Navigator.of(ctx)
.pushNamedAndRemoveUntil(route_c, ModalRoute.withName(route_a)),
),
);
}
}
// route c
class SetMount extends StatelessWidget {
const SetMount({super.key});
#override
Widget build(BuildContext ctx) {
return Scaffold(
body: InkWell(
child: Text('Set Mount'),
onTap: () {
ReachableData.of(ctx).data.mount = 'Mounted';
// Option 1: pop untill reaches the correct route
// Navigator.of(ctx).popUntil(ModalRoute.withName(route_a));
// Option 2: a regular pop
Navigator.of(ctx).pop();
},
),
);
}
}
I am building an app as a project for university and one of the requirements is to play videos within the app.
I have links to exercise videos (bicep curls and so on) stored in a column of a table in SQLite.
I am using Moor in order to interact with the database.
I have the following screen where I am trying to have the video referred in the link from the database play:
class ExerciseVideoTab extends StatefulWidget {
final int exerciseId;
ExerciseVideoTab(this.exerciseId);
#override
_ExerciseVideoTabState createState() => _ExerciseVideoTabState();
}
class _ExerciseVideoTabState extends State<ExerciseVideoTab> {
VideoPlayerController _controller;
Future<void> _initializeVideoPlayerFuture;
String _exerciseVideoLink;
#override
void initState() {
super.initState();
locator<MoorDB>().getExerciseById(widget.exerciseId).then((value) =>
_exerciseVideoLink = value.exerciseVideoLink);
_controller = VideoPlayerController.network(_exerciseVideoLink.toString());
_initializeVideoPlayerFuture = _controller.initialize();
print(_exerciseVideoLink); // prints null for some reason
}
#override
void dispose() {
// Ensure disposing of the VideoPlayerController to free up resources.
_controller.dispose();
super.dispose();
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(child: FutureBuilder(
future: _initializeVideoPlayerFuture,
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.done) {
// If the VideoPlayerController has finished initialization, use
// the data it provides to limit the aspect ratio of the video.
return AspectRatio(
aspectRatio: _controller.value.aspectRatio,
// Use the VideoPlayer widget to display the video.
child: VideoPlayer(_controller),
);
} else {
// If the VideoPlayerController is still initializing, show a
// loading spinner.
return Center(child: CircularProgressIndicator());
}
}
)
),
floatingActionButton: FloatingActionButton(
onPressed: () {
// Wrap the play or pause in a call to `setState`. This ensures the
// correct icon is shown.
setState(() {
// If the video is playing, pause it.
if (_controller.value.isPlaying) {
_controller.pause();
} else {
// If the video is paused, play it.
_controller.play();
}
});
},
// Display the correct icon depending on the state of the player.
child: Icon(
_controller.value.isPlaying ? Icons.pause : Icons.play_arrow,
),
),
);
}
}
I am trying to consume the Future<Exercise> that is returned by the getExerciseById(int id) method and assign the exerciseVideoLink column value to the local _exerciseVideoLink and then use that String to initialize the VideoPlayerController with the link contained within.
The implementation of getExerciseById(int id) is the following:
Future<Exercise> getExerciseById(int id) {
return (select(exercises)..where((exercise) => exercise.exerciseId.equals(id))).getSingle();
}
My problem right now is that after consuming the Future<Exercise> and assigning its exerciseVideoLink attribute to the local String variable, the variable becomes null as soon as the .then((value) => ... function is over and thus, the initialization of the VideoPlayerController fails because the URI is null.
Why is that? How can I make it so that I can consume the Future<Exercise> and use its exerciseVideoLink in order to pass it to the VideoPlayerController?
Your _controller depends on the result of getExerciseById() so you need to wait for that Future to complete before you can assign it. You may find async/await syntax a bit easier to read when working with lots of nested Futures.
An example implementation could be:
#override
void initState() {
super.initState();
_init(); // split out a separate method, initState cannot be async
}
Future<void> _init() async {
final exercise = await locator<MoorDB>().getExerciseById(widget.exerciseId);
_controller = VideoPlayerController.network(exercise.exerciseVideoLink.toString());
_initializeVideoPlayerFuture = _controller.initialize();
}
I have been learning flutter for 2-3 months now and I feel I have a reached a fundamental roadblock with understanding state management. This post will be long unfortunately so please bare with me and I hope I put the right detail.
Problem Definition
I have a list of widgets in a shopping cart,im at the point where I click minus and it only has 1 left the widget must be removed.No matter what I try I cant get that widget to be removed. If I click back button and go back into cart the Item will not appear anymore.
I have considered other methods, like disposing the widget(that didn't seem to work) and I was busy implementing Visibility Show/hide widgets in Flutter programmatically
but that doesn't feel like the right way.If my understanding of providers,changeNotifiers,async and future builders,is correct the below method should work and I think its fundamental to my flutter journey to understand why it doesn't work.
Overview:The idea was to use the minus button on CartItemWidget to call a method that updates Json stored on the local device, then repopulate the List cartProdList in ProductProvider which calls
notifyListeners() and then should propagate everywhere the provider is used. Now I have used this pattern successfully 5 times now, the only different this time is it will be removing a widget which I haven't done before. But this should work dynamically if the future is based of the same provider right ?
function call order
CartItemWidget.onPressed:()
calls >>>
ProductProvider.cartMinusOne(String id)
calls >>>
ProductProvider.Future<List<Product>> cartProducts()
well here goes the code.I also wouldn't mind comments on things I could be doing better in all areas.
CartWidget
class CartWidget extends StatefulWidget {
#override
_CartWidgetState createState() => _CartWidgetState();
}
class _CartWidgetState extends State<CartWidget> {
var providerOfProd;
ProductProvider cartProdProvider = new ProductProvider();
#override
void initState() {
_productsList = new ProductsList();
super.initState();
providerOfProd = Provider.of<ProductProvider>(context, listen: false).cartProducts();
}
#override
Widget build(BuildContext context) {
........
Column(children: <Widget>[
FutureBuilder(
future: providerOfProd,
builder: (context, snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.waiting:
return Container(
width: 0,
height: 0,
);
case ConnectionState.done:
return ListView.separated(
..............
},
itemBuilder: (context, index) {
return CartItemWidget(
product: cartProdProvider.cartProdList.elementAt(index),
heroTag: 'cart',
quantity: cartProdProvider.cartProdList.elementAt(index).cartqty,
key: UniqueKey(),
);
},
);
.........
CartItemWidget
class CartItemWidget extends StatefulWidget {
CartItemWidget({Key key, this.product, this.heroTag, this.quantity = 1}) : super(key: key);
// ProductProvider cartProd = new ProductProvider();
String heroTag;
Product product;
int quantity;
#override
_CartItemWidgetState createState() => _CartItemWidgetState();
}
class _CartItemWidgetState extends State<CartItemWidget> {
#override
Widget build(BuildContext context) {
return Consumer<ProductProvider>(
builder: (context, productProv, _) => InkWell(
child: Container(
.............
child: Row(
children: <Widget>[
.............
IconButton(
onPressed: () {
setState(() {
productProv.cartMinusOne(widget.product.id);
widget.quantity = this.decrementQuantity(widget.quantity);
});
}
.............
ProductProvider
class ProductProvider with ChangeNotifier {
ProductProvider() {
cartProducts();
}
List<Product> cartProdList;
cartMinusOne(String id) async {
//Code to minus item,then return as a string to save as local jason
var test = jsonEncode(cartList);
saveLocalJson(test, 'cart.json');
cartProducts();
notifyListeners();
}
Future<List<Product>> cartProducts() async {
String jsonString = await JsonProvider().getProductJson();
String cartString = await getCartJson();
var filterProdList = (json.decode(jsonString) as List).map((i) => Product.fromJson(i)).toList();
//code to get match cart list to product list
cartProdList = filterProdList.where((element) => element.cartqty > 0).toList();
notifyListeners();
return cartProdList;
}
........................
I have an API that returns content and I put this content in a GridView.builder to allow pagination.
I have architected the page in such a way that I have a FutureBuilder on a stateless widget and when the snapshot is done I then pass the snapshot data to a stateful widget to build the grid.
It is all working fine, however I want now to implement a functionality that allows me to reload the widget by placing a reload icon when snapshot has error and on click reloading widget. How can I accomplish this?
The following is my FutureBuilder on my Stateless widget:
return new FutureBuilder<List<Things>>(
future: apiCall(),
builder: (context, snapshot) {
if (snapshots.hasError)
return //Reload Icon
switch (snapshots.connectionState) {
case ConnectionState.waiting:
return Center(child: CircularProgressIndicator());
case ConnectionState.done:
return StatefulWidhet(things: snapshot.data);
default:
}
});
}
You'll need to lift the state up. The whole loading concept is abstracted by the FutureBuilder, but because you don't want to do one-time-loading, that's not the right abstraction layer for you. That means, you'll need to implement the "waiting for the future to complete and then build stuff" yourself in order to be able to trigger the loading repeatedly.
For example, you could put everything in a StatefulWidget and have isLoading, data and error properties and set these correctly.
Because this is probably a recurring task, you could even create a widget to handle that for you:
import 'package:flutter/material.dart';
class Reloader<T> extends StatefulWidget {
final Future<T> Function() loader;
final Widget Function(BuildContext context, T data) dataBuilder;
final Widget Function(BuildContext context, dynamic error) errorBuilder;
const Reloader({
Key key,
this.loader,
this.dataBuilder,
this.errorBuilder,
}) : super(key: key);
#override
State<StatefulWidget> createState() => ReloaderState<T>();
static of(BuildContext context) =>
context.ancestorStateOfType(TypeMatcher<ReloaderState>());
}
class ReloaderState<T> extends State<Reloader<T>> {
bool isLoading = false;
T data;
dynamic error;
#override
void initState() {
super.initState();
reload();
}
Future<void> reload() async {
setState(() {
isLoading = true;
data = null;
error = null;
});
try {
data = await widget.loader();
} catch (error) {
this.error = error;
} finally {
setState(() => isLoading = false);
}
}
#override
Widget build(BuildContext context) {
if (isLoading) {
return Center(child: CircularProgressIndicator());
}
return (data != null)
? widget.dataBuilder(context, data)
: widget.errorBuilder(context, error);
}
}
Then, you can just do
Reloader(
loader: apiCall,
dataBuilder: (context, data) {
return DataWidget(things: data);
},
errorBuilder: (context, error) {
return ...
RaisedButton(
onPressed: () => Reloader.of(context).reload(),
child: Text(reload),
),
...;
},
)
Also, I wrote a package for that case which has some more features built-in and uses a controller-based architecture instead of searching the state through Reload.of(context): flutter_cached
With it, you could just do the following:
In a state, create a CacheController (although you don't need to cache things):
var controller = CacheController(
fetcher: apiCall,
saveToCache: () {},
loadFromCache: () {
throw 'There is no cache!';
},
),
Then, you could use that controller to build a CachedBuilder in the build method:
CachedBuilder(
controller: controller,
errorScreenBuilder: (context, error) => ...,
builder: (context, items) => ...,
...
),
When the reload button is pressed, you can simply call controller.fetch(). And you'll also get some cool things like pull-to-refresh on top.
I'm using an inherited Widget to access a Bloc with some long running task (e.g. search).
I want to trigger the search on page 1 and continue to the next page when this is finished. Therefore I'm listening on a stream and wait for the result to happen and then navigate to the result page.
Now, due to using an inherited widget to access the Bloc I can't access the bloc with context.inheritFromWidgetOfExactType() during initState() and the exception as I read it, recommends doing this in didChangeDependencies().
Doing so this results in some weird behavior as the more often I go back and forth, the more often the stream I access fires which would lead to the second page beeing pushed multiple times. And this increases with each back and forth interaction. I don't understand why the stream why this is happening. Any insights here are welcome. As a workaround I keep a local variable _onSecondPage holding the state to avoid pushing several times to the second Page.
I found now How to call a method from InheritedWidget only once? which helps in my case and I could access the inherited widget through context.ancestorInheritedElementForWidgetOfExactType() and just listen to the stream and navigate to the second page directly from initState().
Then the stream behaves as I would expect, but the question is, does this have any other side effects, so I should rather get it working through listening on the stream in didChangeDependencides() ?
Code examples
My FirstPage widget listening in the didChangeDependencies() on the stream. Working, but I think I miss something. The more often i navigate from first to 2nd page, the second page would be pushed multiple times on the navigation stack if not keeping a local _onSecondPage variable.
#override
void didChangeDependencies() {
super.didChangeDependencies();
debugPrint("counter: $_counter -Did change dependencies called");
// This works the first time, after that going back and forth to the second screen is opened several times
BlocProvider.of(context).bloc.finished.stream.listen((bool isFinished) {
_handleRouting(isFinished);
});
}
void _handleRouting(bool isFinished) async {
if (isFinished && !_onSecondPage) {
_onSecondPage = true;
debugPrint("counter: $_counter - finished: $isFinished : ${DateTime.now().toIso8601String()} => NAVIGATE TO OTHER PAGE");
await Navigator.push(
context,
MaterialPageRoute(builder: (context) => SecondRoute()),
);
_onSecondPage = false;
} else {
debugPrint("counter: $_counter - finished: $isFinished : ${DateTime.now().toIso8601String()} => not finished, nothing to do now");
}
}
#override
void dispose() {
debugPrint("counter: $_counter - disposing my homepage State");
subscription?.cancel();
super.dispose();
}
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'You have pushed the button this many times:',
),
StreamBuilder(
stream: BlocProvider.of(context).bloc.counter.stream,
initialData: 0,
builder: (context, snapshot) {
_counter = snapshot.data;
return Text(
"${snapshot.data}",
style: Theme.of(context).textTheme.display1,
);
},
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
),
);
}
}
A simple Bloc faking some long running work
///Long Work Bloc
class LongWorkBloc {
final BehaviorSubject<bool> startLongWork = BehaviorSubject<bool>();
final BehaviorSubject<bool> finished = BehaviorSubject<bool>();
int _counter = 0;
final BehaviorSubject<int> counter = BehaviorSubject<int>();
LongWorkBloc() {
startLongWork.stream.listen((bool start) {
if (start) {
debugPrint("Start long running work");
Future.delayed(Duration(seconds: 1), () => {}).then((Map<dynamic, dynamic> reslut) {
_counter++;
counter.sink.add(_counter);
finished.sink.add(true);
finished.sink.add(false);
});
}
});
}
dispose() {
startLongWork?.close();
finished?.close();
counter?.close();
}
}
Better working code
If I however remove the code to access the inherited widget from didChangeDependencies() and listen to the stream in the initState() it seems to be working properly.
Here I get hold of the inherited widget holding the stream through context.ancestorInheritedElementForWidgetOfExactType()
Is this ok to do so? Or what would be a flutter best practice in this case?
#override
void initState() {
super.initState();
//this works, but I don't know if this is good practice or has any side effects?
BlocProvider p = context.ancestorInheritedElementForWidgetOfExactType(BlocProvider)?.widget;
if (p != null) {
p.bloc.finished.stream.listen((bool isFinished) {
_handleRouting(isFinished);
});
}
}
Personally, I have not found any reason not to listen to BLoC state streams in initState. As long as you remember to cancel your subscription on dispose
If your BlocProvider is making proper use of InheritedWidget you should not have a problem getting your value inside of initState.
like So
void initState() {
super.initState();
_counterBloc = BlocProvider.of(context);
_subscription = _counterBloc.stateStream.listen((state) {
if (state.total > 20) {
Navigator.push(context,
MaterialPageRoute(builder: (BuildContext context) {
return TestPush();
}));
}
});
}
Here is an example of a nice BlocProvider that should work in any case
import 'package:flutter/widgets.dart';
import 'bloc_base.dart';
class BlocProvider<T extends BlocBase> extends StatefulWidget {
final T bloc;
final Widget child;
BlocProvider({
Key key,
#required this.child,
#required this.bloc,
}) : super(key: key);
#override
_BlocProviderState<T> createState() => _BlocProviderState<T>();
static T of<T extends BlocBase>(BuildContext context) {
final type = _typeOf<_BlocProviderInherited<T>>();
_BlocProviderInherited<T> provider =
context.ancestorInheritedElementForWidgetOfExactType(type)?.widget;
return provider?.bloc;
}
static Type _typeOf<T>() => T;
}
class _BlocProviderState<T extends BlocBase> extends State<BlocProvider<BlocBase>> {
#override
Widget build(BuildContext context) {
return _BlocProviderInherited<T>(
bloc: widget.bloc,
child: widget.child,
);
}
#override
void dispose() {
widget.bloc?.dispose();
super.dispose();
}
}
class _BlocProviderInherited<T> extends InheritedWidget {
final T bloc;
_BlocProviderInherited({
Key key,
#required Widget child,
#required this.bloc,
}) : super(key: key, child: child);
#override
bool updateShouldNotify(InheritedWidget oldWidget) => false;
}
... and finally the BLoC
import 'dart:async';
import 'bloc_base.dart';
abstract class CounterEventBase {
final int amount;
CounterEventBase({this.amount = 1});
}
class CounterIncrementEvent extends CounterEventBase {
CounterIncrementEvent({amount = 1}) : super(amount: amount);
}
class CounterDecrementEvent extends CounterEventBase {
CounterDecrementEvent({amount = 1}) : super(amount: amount);
}
class CounterState {
final int total;
CounterState(this.total);
}
class CounterBloc extends BlocBase {
CounterState _state = CounterState(0);
// Input Streams/Sinks
final _eventInController = StreamController<CounterEventBase>();
Sink<CounterEventBase> get events => _eventInController;
Stream<CounterEventBase> get _eventStream => _eventInController.stream;
// Output Streams/Sinks
final _stateOutController = StreamController<CounterState>.broadcast();
Sink<CounterState> get _states => _stateOutController;
Stream<CounterState> get stateStream => _stateOutController.stream;
// Subscriptions
final List<StreamSubscription> _subscriptions = [];
CounterBloc() {
_subscriptions.add(_eventStream.listen(_handleEvent));
}
_handleEvent(CounterEventBase event) async {
if (event is CounterIncrementEvent) {
_state = (CounterState(_state.total + event.amount));
} else if (event is CounterDecrementEvent) {
_state = (CounterState(_state.total - event.amount));
}
_states.add(_state);
}
#override
void dispose() {
_eventInController.close();
_stateOutController.close();
_subscriptions.forEach((StreamSubscription sub) => sub.cancel());
}
}