Flutter Course: 14.2 Asynchronous Method

The Importance of Asynchronous Programming

Asynchronous programming is an essential element in modern application development. In particular, asynchronous tasks are very important for improving user experience (UX) and increasing responsiveness. The asynchronous approach allows multiple tasks to be performed simultaneously, enabling the execution of other tasks while waiting for one task to complete. This enables users to use applications that are faster and smoother.

Asynchronous Programming in Flutter

Asynchronous programming in Flutter is primarily implemented through the Future and async/await keywords. Flutter is written in the Dart programming language and offers various features to facilitate asynchronous programming easily. Now, let’s take a look at how to use asynchronous functions in Flutter.

Future and Asynchronous Functions

Future is a class that represents the result of an asynchronous operation. A Future object represents a task that will complete in the future and is returned from an asynchronous function. An asynchronous function is defined with the async keyword, and it uses the await keyword internally to wait for the Future to complete.

Asynchronous Function Example

Future fetchData() async {
    await Future.delayed(Duration(seconds: 2));
    return "Data loading completed!";
}
            

The example above is an asynchronous function that returns the string “Data loading completed!” after waiting for 2 seconds.

Usage of await

The await keyword causes execution to wait until the Future is completed, enabling the sequential execution of asynchronous code. For example, here’s how to call the fetchData function above.

await Example

void main() async {
    print("Loading data...");
    String result = await fetchData();
    print(result);
}
            

The main function is also defined as async, and it uses await to wait for the result of the fetchData function. This allows the message “Loading data…” to be printed immediately, and after 2 seconds, “Data loading completed!” is printed.

Error Handling in Asynchronous Tasks

Error handling in asynchronous tasks is an important aspect. You can handle exceptions occurring in asynchronous functions using a try-catch block.

Error Handling Example

Future fetchWithError() async {
    throw Exception("An error occurred!");
}

void main() async {
    try {
        String result = await fetchWithError();
        print(result);
    } catch (e) {
        print("Error: ${e.toString()}");
    }
}
            

In the example above, the fetchWithError function throws an exception. The main function wraps the call to that function in a try-catch block to handle the error.

Various Methods to Manage Future

To manage asynchronous processing more effectively in Flutter, there are methods provided to execute multiple Futures simultaneously. Using the Future.wait method makes it possible to wait for multiple Futures at the same time.

Future.wait Example

Future fetchAllData() async {
    var first = fetchData();
    var second = fetchWithError();
    var results = await Future.wait([first, second]);

    print(results);
}

void main() async {
    try {
        await fetchAllData();
    } catch (e) {
        print("Error: ${e.toString()}");
    }
}
            

The fetchAllData function executes two Futures simultaneously and waits for the results. If the second Future throws an error, the catch block handles the error.

Utilizing Streams

A stream is used to handle the continuous flow of asynchronous data. It is useful in scenarios where data is generated continuously, such as websocket connections, file reading, or database queries. Streams handle a series of events asynchronously.

Stream Example

Stream numberStream() async* {
    for (int i = 0; i < 5; i++) {
        await Future.delayed(Duration(seconds: 1));
        yield i;
    }
}

void main() async {
    await for (var number in numberStream()) {
        print(number);
    }
}
            

The numberStream function creates a stream and outputs a number every second. The main function uses the await for keyword to access the data from the stream.

Best Practices in Asynchronous Programming

When engaging in asynchronous programming, it is important to follow several best practices:

• Error Handling: Don’t forget to handle exceptions in asynchronous functions.
• Combining Futures: Use Future.wait and Future.any to efficiently handle multiple tasks.
• Using Streams: Consider streams when continuous data processing is needed.