flutter - realtime stream data from REST API

Question

I am retrieving data from a REST API using a stream, but when the data updates in the database the stream does not refresh the data in the app.

StreamController _productsController = new StreamController();
...         
//products is a list that contains the data
_productsController.add(products);
...
body: Container(
        child: StreamBuilder(
            stream: _productsController.stream,
            builder: (BuildContext context, AsyncSnapshot snapshot) {...}

I saw a solution proposing to periodically re-load the data from the API, for example each 1 second.

Timer.periodic(Duration(seconds: 1), (_) => loadDetails());

Source: Stream for API coming from PHP in Flutter (Not Firebase)

I do not think it is an efficient approach. In my app for example, I want to integrate the data changes without re-loading the data.

Is there an efficient way to make the stream reflects data changes in the app without reloading data?

@ZeffryReynando you can use a timer, but its not an efficient approach, or use socket in case its applicable, otherwise use another alternative such as firebase/firestore for realtime — EddyG, Jul 24 '20 at 19:22

score 16 · Accepted Answer · answered Oct 08 '20 at 07:41

16

You can implement your own stream with dart as shown in the docs

With this, you will also need a delay and you will be making calls to the API periodically, but I guess that's the way to go if your API does not send any message without calling it first.

Stream<Product> productsStream() async* {
  while (true) {
    await Future.delayed(Duration(milliseconds: 500));
    Product someProduct = getProductFromAPI();
    yield someProduct;
  }
}

A little explanation of the code:

You need a loop to call the API periodically. Don't worry about infinite loops, since the stream will only be used while the StreamBuild that calls it is built.
The yield keyword is like the return when using streams

Then, to use it, just implement a StreamBuilder calling the Stream you just created:

StreamBuilder(
    stream: productsStream(),
    builder: (BuildContext context, AsyncSnapshot<Product> snapshot) {...}
)

answered Oct 08 '20 at 07:41

jsgalarraga

425
6
13

Will it work when app is death ?, means app is installed in phone but not using or running on background – Mukta Dec 05 '20 at 00:44
@Mukta no, streams implemented this way only update while the widget is built. I'm not sure if making some changes you can make it update while running on background – jsgalarraga Dec 06 '20 at 11:48
@jsgalarraga what if I am calling the `Stream` in `initState` of a StatefulWidget. Will it run in background? – MohitC May 18 '22 at 19:39
@jsgalarraga This was working fine for a couple of seconds(like 40-45 seconds) and updating the list, but after that circular loader comes and loader seems to load infinitely. – KJEjava48 May 26 '23 at 07:21

flutter - realtime stream data from REST API

1 Answers1