Mastering Asynchronous Programming in Flutter: A Complete Guide to Streams, Await, Async.

NACHIKETA PANDEY Tuesday, February 07, 2023

Asynchronous programming is a fundamental concept in modern software development, and it is particularly important in Flutter, a framework for building high-performance, high-fidelity, mobile and web applications. In this article, we’ll explore asynchronous programming in Flutter, including streams, await, and async.

What is Asynchronous Programming?

Asynchronous programming is a way of writing code that can handle multiple tasks in parallel. This allows you to keep your app responsive, even when performing long-running tasks like network requests or file operations. In asynchronous programming, you write your code in a way that enables it to run multiple tasks at the same time, without blocking the main thread.

Why is Asynchronous Programming Important in Flutter?

Flutter is designed to be fast and responsive, and asynchronous programming plays a big role in achieving this goal. By using asynchronous programming, you can keep your app responsive, even when it’s performing long-running tasks, without the need for multiple threads. This makes it easier to write high-performance apps that feel fast and responsive to the user.

Streams in Flutter:

A stream is a sequence of asynchronous events. In Flutter, streams are used to represent a continuous flow of data, like the flow of data from a server, or the flow of data from a user’s gestures. Streams are a powerful tool for building responsive apps, because they allow you to handle a continuous flow of data in an asynchronous way.

To use streams in Flutter, you’ll need to create a StreamController and a StreamBuilder. The StreamController is responsible for emitting data to the stream, while the StreamBuilder is responsible for listening to the stream and updating the UI.

Here is a simple example of how to use streams in Flutter:

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
 }

class _MyHomePageState extends State<MyHomePage> {
  StreamController<int> _streamController;
  @override
  void initState() {
    super.initState();
    _streamController = StreamController<int>();
  }
  @override
  void dispose() {
    _streamController.close();
    super.dispose();
  }
  void _addDataToStream() {
    _streamController.add(1);
  }
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: StreamBuilder(
        stream: _streamController.stream,
        builder: (context, snapshot) {
          return Center(
            child: Text(snapshot.data.toString()),
          );
        },
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _addDataToStream,
        child: Icon(Icons.add),
      ),
    );
  }
   }

In this example, we create a StreamController in the initState method, and then close it in the dispose method. The StreamBuilder listens to the stream, and updates the UI with the latest data from the stream.

Await and Async :

In Dart and Flutter, you can use the await keyword to wait for an asynchronous operation to complete. The await keyword is used in conjunction with the async keyword. When you use the async keyword on a function, you are telling Dart that the function may contain asynchronous code that should be executed in a separate, non-blocking task.

Here is an example of how to use await and async in Flutter:

Future<int> fetchData() async {
  await Future.delayed(Duration(seconds: 3));
  return 42;
 }

 void main() {
  fetchData().then((data) => print(data));
  }

In this example, the fetchData function is marked as async, so Dart knows that the function may contain asynchronous code. The fetchData function uses await to wait for a Future to complete, which simulates a long-running task like a network request. The then method is used to handle the result of the Future, which is the int value 42.

Conclusion:

In this article, we’ve explored asynchronous programming in Flutter, including streams, await, and async. Streams are a powerful tool for building responsive apps, and the await and async keywords make it easy to write asynchronous code in Dart. With this knowledge, you’re now ready to start building high-performance, responsive Flutter apps that feel fast and responsive to your users.

App performanceAsyncAsynchronous programmingAwaitDartDart programming languageFlutterMobile app developmentoptimization.StreamsUser experience