Скачать или смотреть Why Android Datastore Always Returns the Same Value with runBlocking

Discover why using `runBlocking` with Android Datastore results in returning the same value, how to resolve the issue, and best practices for accessing value updates in the main thread.
---
This video is based on the question https://stackoverflow.com/q/68275999/ asked by the user 'UmutTekin' ( https://stackoverflow.com/u/7730820/ ) and on the answer https://stackoverflow.com/a/72966824/ provided by the user 'Petr Weissar' ( https://stackoverflow.com/u/10869044/ ) 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: Why Android Datastore always returns same value with runblocking

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.
---
Why Android Datastore Always Returns the Same Value with runBlocking

If you're developing an Android application using Kotlin and Jetpack Datastore, you might encounter a common issue: retrieving the same value multiple times even after making changes. This can be particularly frustrating when trying to work with updated data within fragments. This guide will delve into why this happens and provide you a structured solution to effectively access updated values without the headaches.

Understanding the Problem

When using Datastore to manage preferences such as lastInsertedId, you may notice that after changing its value in one fragment, the same value is returned when you navigate back to another fragment. The main points of confusion include:

Fragment Lifecycle: If a fragment is not destroyed but rather recreated, it may not get the updated data. This is often the case when only onDestroyView is called, which can lead to complexities in data retrieval.

Use of runBlocking: When leveraging runBlocking for retrieving data, it can sometimes lead to stale data being returned, as the coroutine isn't effectively observing changes.

The Common Usage and Mistake

You might have implemented something similar to this in your data management class:

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

This approach often leads to always returning the same value due to how runBlocking operates in relation to coroutines and data flow in Kotlin.

Solution: The Correct Approach

To access the latest value of lastInsertedId, you need to modify how it is defined in your DataStoreManager class. Here’s the adjustment:

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

Why this Works

Get Property: Utilizing get() in the property definition ensures that each time lastInsertedId is accessed, it runs the code block to retrieve the current data from the Datastore.

Updated Data Retrieval: The coroutine block inside get() will always fetch the most recent value from the datastore, ensuring that any changes are reflected immediately when accessed.

Best Practices for Data Access

While the modification above helps in retrieving the latest value, here are some best practices to enhance your DataStore interactions:

Use Flow for Real-Time Updates: Instead of relying solely on runBlocking, consider using Flow for instances where you want to observe changes in the datastore reactively:

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

This allows your app's UI to automatically update when the data changes, eliminating the need for manual refreshes.

UI Updates on Main Thread: Always ensure that you observe or collect from your Flow on the main thread to prevent UI blocking operations from the background threads.

Fragment Lifecycle Management: Be mindful of the fragment lifecycle and consider using LiveData or ViewModel patterns to manage state efficiently across configuration changes and lifecycle events.

Conclusion

Using Android Datastore effectively requires an understanding of coroutines and state management within your application's lifecycle. By simply adjusting how you retrieve values from the datastore, you can resolve the issue of stale data. Implementing reactive principles with Flows will further enhance your app's performance and responsiveness. With these techniques, you can ensure that you access lastInsertedId correctly and efficiently, no matter where you are in your application. Happy coding!