Скачать или смотреть Resolving the RecyclerView Null Object Reference Error in Android

Discover how to fix the `RecyclerView` null object reference error that occurs when repopulating data in your Android app. Learn the necessary steps to ensure your data displays correctly without crashing.
---
This video is based on the question https://stackoverflow.com/q/62781767/ asked by the user 'Paras Rajora' ( https://stackoverflow.com/u/13424279/ ) and on the answer https://stackoverflow.com/a/62788701/ provided by the user 'Franz Andel' ( https://stackoverflow.com/u/9188214/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: RecyclerView null object reference error when repopulate

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Resolve the RecyclerView Null Object Reference Error in Android

The RecyclerView is a powerful tool for displaying scrollable lists of data in Android applications. However, developers often face challenges when trying to repopulate data in a RecyclerView. One common error is the null object reference issue, which can lead to frustrating crashes and inconsistent behavior. In this guide, we'll delve into this issue and provide a step-by-step solution to get your RecyclerView back on track.

The Problem: Null Object Reference Error

When repopulating the RecyclerView, you might encounter errors like:

Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView$LayoutManager.setExactMeasureSpecsFrom(android.support.v7.widget.RecyclerView)' on a null object reference

RecyclerView$LayoutManager.onLayoutChildren(android.support.v7.widget.RecyclerView$Recycler, android.support.v7.widget.RecyclerView$State)' on a null object reference

These errors often occur when the RecyclerView is null at the time you attempt to update its contents, usually because operations on the UI must be conducted on the UI thread.

The Solution: Running UI Operations on the Main Thread

To solve the null object reference error, you need to ensure that any updates to the RecyclerView are executed on the UI thread. This can be achieved using the runOnUiThread method within your background operations. Below, we’ll go through the necessary steps to implement this method correctly.

Step 1: Update doInBackground

In your AsyncTask, where you move data fetching to a background thread, you will need to wrap your RecyclerView manipulation logic in a runOnUiThread method call. Here’s how you can do that:

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

Step 2: Avoid Updating the Adapter in doInBackground

While it's tempting to update your RecyclerView directly from doInBackground, it is crucial that updates only occur on the UI thread. Handling the data-fetching operation in the background is fine, but use a callback or similar mechanism to pass the data back to the UI thread safely.

Step 3: Observing Results and Testing

After making these changes, test your application thoroughly. Ensure that clicking the "get data" button and any other UI operations do not lead to crashes.

Conclusion

Handling the RecyclerView effectively requires an understanding of threading and properly managing the UI updates. By ensuring that all interactions with the RecyclerView take place on the UI thread, you can eliminate the frustrating null object reference errors and create a more stable and user-friendly application.

If you follow these steps, you should have a working solution to your RecyclerView issues. Happy coding!