Скачать или смотреть Solving the LazyColumn Not Updating Issue in Android Development

Learn how to properly update your `LazyColumn` in Android when using ViewModel, Room, Flow, and collectAsStateWithLifecycle in Jetpack Compose.
---
This video is based on the question https://stackoverflow.com/q/75143625/ asked by the user 'SageJustus' ( https://stackoverflow.com/u/14887783/ ) and on the answer https://stackoverflow.com/a/75143913/ provided by the user 'Jolan DAUMAS' ( https://stackoverflow.com/u/13115358/ ) 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: LazyColumn is not updated when the data is changed

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.
---
Solving the LazyColumn Not Updating Issue in Android Development

As you venture into Android development, you may encounter various challenges, one of which is ensuring that your UI updates seamlessly when the underlying data changes. A common situation arises when using Jetpack Compose's LazyColumn with Room, ViewModel, and Flow. Many developers ask: Why doesn't my LazyColumn update when new data is added to the database?

In this guide, we'll dissect the issue and provide you with a structured solution to make sure that when you add new data, your user interface reflects those changes in real-time.

The Problem Defined

When using Room to manage your database and Jetpack Compose for your UI, many developers opt to work with a LazyColumn to display a list of items. In the initial implementation, if new items are added to the database, the LazyColumn does not automatically refresh to show this new data. In fact, the UI appears updated only after navigating back to the application after pressing the Home button.

This frustrating behavior typically stems from the way data is fetched from Room and how updates are managed in your application architecture.

Understanding the Cause

The core issue lies in the use of the -Query method in your DAO (Data Access Object). If you define a function that returns a simple list of articles, the UI will only pull data once, and won't listen for updates from the database as new entries are added.

Here’s a key observation:

Using List<Article> means fetching the data only once.

The UI needs a way to listen for changes.

The Solution: Use Flow

To properly handle real-time updates, we can leverage Kotlin's Flow, which allows our application to react to changes in the database as they happen. This way, whenever we add an article, the LazyColumn will receive updates automatically, leading to a smooth user experience.

Code Breakdown

Update Your DAO: Change your DAO method to return Flow<List<Article>>.

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

Modify the Repository: Ensure the getAll() function in your repository utilizes the updated DAO method.

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

Implement in Your ViewModel: Your ViewModel is already set to collect the flow correctly.

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

Update Your Composable Activity: Finally, in your Composable function, ensure you are collecting the articles state correctly.

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

Conclusion

By switching your DAO to return Flow<List<Article>> instead of List<Article>, your application now correctly listens for updates from the database. This will ensure that any time new data is added, your LazyColumn automatically updates to display the latest information.

With this adjustment, you can enjoy a more responsive user interface, enhancing the overall user experience in your Android application. This approach is vital as you continue to build upon your knowledge of Android development, especially when employing modern architectures like MVVM with Jetpack Compose.

Happy coding!