Скачать или смотреть Resolving onBindViewHolder Not Triggering for RecyclerView Items

Discover why `onBindViewHolder` isn't called for non-visible items in Android's RecyclerView and learn how to implement a solution effectively.
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This video is based on the question https://stackoverflow.com/q/63265202/ asked by the user 'Ravi Kiran' ( https://stackoverflow.com/u/11363529/ ) and on the answer https://stackoverflow.com/a/63467832/ provided by the user 'Ravi Kiran' ( https://stackoverflow.com/u/11363529/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem: Why onBindViewHolder Isn't Triggering

If you're working with Android's RecyclerView to display a list of items and you've encountered an issue where onBindViewHolder isn't triggered for items that aren't currently visible, you're not alone. This is a common hiccup when dealing with RecyclerViews, especially when updating the list of items dynamically.

The Scenario:
You've created a RecyclerView with 10 items, and while scrolling to the bottom of the list, you attempt to update the first item using notifyItemChanged(pos) for an item that isn't currently displayed on the screen. However, you notice that onBindViewHolder() isn’t being called. This leaves you wondering why your changes aren't reflected in the UI.

The Technical Explanation

Why onBindViewHolder() Is Not Triggered

The core of the issue lies in how RecyclerView manages items. Since RecyclerView optimizes memory usage by recycling view holders, it does not reuse the view holder for items that aren't currently visible on the screen. This means:

Recycled Items: If the item is off-screen, its view holder may not be bound again to represent its new data when you call notifyItemChanged(pos).

Updates Not Reflected: Since the view isn't being recreated, any changes made to the data model won't reflect in the UI.

The Solution: Properly Updating Items in the RecyclerView

Fortunately, the solution involves tweaking how you manage data updates in your RecyclerView. Here are the steps to ensure changes are applied correctly:

1. Update the Data Source

Instead of relying solely on notifyItemChanged(pos), you should consider updating your list of items directly.

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

2. Notify the Adapter

After you have modified the underlying data source, call notifyDataSetChanged() to refresh the entire list of displayed items.

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

Why This Works:

Data Consistency: By updating the source and notifying the adapter, you ensure the view is in sync with your data.

Rebinding View Holders: Calling notifyDataSetChanged() ensures that all view holders are re-bound, even those that are off-screen.

Conclusion

Handling item updates in a RecyclerView can be tricky, especially when working with dynamic data and scrolling. Understanding how the RecyclerView lifecycle integrates with data binding is crucial for creating responsive user interfaces.

If you encounter issues where onBindViewHolder does not seem triggered for non-visible items, remember to:

Update your data source.

Use notifyDataSetChanged() to refresh the view.

By following these best practices, you will ensure your RecyclerView reflects the most accurate and up-to-date information to your users.