Solving the NetworkOnMainThreadException in Android's AsyncTask: A Guide for Developers

Discover the common pitfall of the `NetworkOnMainThreadException` in Android development. Learn how to properly use AsyncTask to fetch data from APIs without causing your app to crash.
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Solving the NetworkOnMainThreadException in Android's AsyncTask

When developing Android applications, dealing with data fetching is a common task. However, you might encounter a frustrating problem: the NetworkOnMainThreadException. This issue occurs when an application attempts to perform network operations on the main thread, leading to app crashes.

If you find yourself facing this issue while trying to fetch earthquake data for your app, don’t worry; we’re here to help you understand the problem and quite simply, how to resolve it.

Understanding the Problem

In Android, to maintain a responsive user interface, network operations must not occur on the main thread (UI thread). If done, this results in the NetworkOnMainThreadException. In your case, you might be encountering this exception because you are trying to fetch the data twice:

Once in the doInBackground method of the AsyncTask, where it is expected.

Again in the updateUi method, which runs on the UI thread after the background task completes.

Error Log Example

Here's a snippet from your error log:

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

This indicates that your app violates the rules of conducting network operations on the main thread.

Solution Breakdown

To solve this issue, you need to ensure that network calls occur only within the doInBackground method of your AsyncTask, and not in the UI-related methods like updateUi.

Step-by-Step Solution

Remove the duplicate API call from updateUi:
You should modify your updateUi method to solely handle the data passed to it from doInBackground. Here’s the updated code for your updateUi method:

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

With this modification, the updateUi method no longer fetches data. It simply updates the UI with the List of Earthquakes that is passed to it by the onPostExecute method.

Verify the AsyncTask Implementation:
Ensure that your AsyncTask is set up as shown below. The doInBackground method fetches data once, thus keeping the UI responsive.

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

Now, your app should no longer throw the NetworkOnMainThreadException.

Conclusion

By restructuring your AsyncTask and ensuring that network calls only occur in the doInBackground method, you can prevent your Android application from crashing due to NetworkOnMainThreadException. Remember, the key to asynchronous programming in Android is keeping the main thread free for UI interactions while leveraging background threads for intensive tasks.

With these adjustments, fetching data for your earthquake application should be smooth and hassle-free. Happy coding!