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Learn how to handle network calls with coroutines in Jetpack Compose to avoid exceptions and improve your app's performance.
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How to Properly Use Coroutines in Composable Functions for Network Calls

When developing Android applications using Jetpack Compose, it’s common to face issues when executing network calls directly in Composable functions. A typical error encountered is the NetworkOnMainThread exception, which indicates that a background operation is being attempted on the main thread. This guide will delve into a real-world scenario involving a video scraper and how to handle such operations efficiently using Kotlin coroutines with Compose.

The Problem

Imagine you are working on a video scraping application where you want to extract video sources from a URL, and subsequently display them in a dialog using ExoPlayer. The challenge arises when you try to perform the network operation directly within the Composable function.

Here’s a summarized version of the code causing the problem:

[[See Video to Reveal this Text or Code Snippet]]

As a result, you are left with the NetworkOnMainThread exception that signifies an attempt to perform network operations on the main thread.

The Solution

Using State Variables and LaunchedEffect

The ideal way to resolve this issue is by offloading the network operation to a background thread using coroutines. You can leverage LaunchedEffect for this purpose. This allows the Composable to wait for the result from the coroutine before proceeding to display the video source.

Here’s how you can implement it:

[[See Video to Reveal this Text or Code Snippet]]

Display the Video Player

You can now safely use videoSrc in your VideoPlayer Composable:

[[See Video to Reveal this Text or Code Snippet]]

Handling Events with Coroutine Scopes

If your video scraping should be triggered by user actions like a button click, you should utilize rememberCoroutineScope. This will help you launch the network call in response to specific events.

Here’s an example of how to achieve that with a button:

[[See Video to Reveal this Text or Code Snippet]]

Comprehensive Steps

To summarize, here’s how you can implement the solution:

Define a state variable: This will hold your video source.

Use LaunchedEffect: Initiate your network operation in a background thread.

Update the UI conditionally: Render the VideoPlayer when the video source is available.

Respond to user actions: Trigger your scraping function through button clicks or other interactions using coroutine scope.

Conclusion

Handling network requests in Composable functions doesn’t need to be complicated. By following these outlined steps, you can effectively avoid the pitfalls of performing operations on the main thread. Using Kotlin coroutines with Compose enhances user experience while keeping your application responsive.

If you have any questions or encounter issues in your implementation, feel free to leave a comment below!