Скачать или смотреть Solving the Issue of Flutter App Losing Local Data: Why Shared Preferences May Not Be Enough

Discover why your Flutter app may be losing local data when users close the app and learn effective solutions to prevent this issue with shared preferences and JSON files.
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Solving the Issue of Flutter App Losing Local Data

In the journey of developing a Flutter application, one consistent challenge that developers face is managing local data persistence. This becomes particularly troubling when users report instances where essential data is lost upon closing and reopening the app. Recently, a developer encountered this very problem while using both shared_preferences and writing to a local JSON file. Let's take a closer look at the issue and the solution found.

The Problem: Losing Local Data

The developer began testing their Flutter app with a group of users and quickly discovered an unsettling trend. Users reported that local data was disappearing when they closed and reopened the app. Here's a breakdown of the situation:

The app utilized shared_preferences to store lightweight data and a local JSON file for other information, leveraging path_provider to get the necessary storage paths.

During testing, some users, predominantly on iOS, encountered the problem consistently. When the app was closed, crucial user data was missing when reopened, despite the data remaining intact during the app's runtime.

The developer struggled to replicate the problem in their environment, leading to further investigation. A primary suspect was the method of data storage and the peculiarities associated with it.

Understanding the Solution

After a thorough troubleshooting process, the developer pinpointed that the issue stemmed from the shared_preferences mechanism losing data, particularly on iOS devices. The documentation explicitly advises against using shared_preferences for critical data, and in this instance, it proved to be sage advice.

Migrating to a JSON File

To address the problem, the developer took the following steps:

Identify Critical Data: Recognize which pieces of data are necessary to persist beyond the app's execution.

Switch to JSON Storage: Instead of relying on shared_preferences, the developer migrated critical data points to a local JSON file. This allowed better control over data persistence and integrity.

Implementation: Using the path_provider, the developer stored user data in a locally accessible JSON file format, ensuring that data would not be lost after the app was closed.

Why the Change Matters

Reliability: Storing critical data in a more stable format reduces the risk of data loss, particularly when working with different operating systems like Android and iOS.

Documentation Awareness: The need to consult and heed library documentation is crucial in software development. The warning against using shared_preferences for critical data confirmed by real-world testing cannot be overlooked.

Moving Forward

Developers must adapt their practices based on user feedback and research findings. Here are a few additional tips to avoid local data issues in Flutter:

Use Alternatives: Consider databases like SQLite or Hive for more complex data needs.

Test Across Devices: Always ensure that testing is comprehensive and spans different devices and operating systems.

Regular Data Backups: Implement backup mechanisms if possible to prevent catastrophic data loss.

Conclusion

This case serves as a reminder of the importance of selecting the appropriate methods for data persistence in mobile applications. While shared_preferences may be adequate for saving simple user preferences, relying on it for critical data can lead to frustrating experiences for users. By migrating to a more reliable storage option, developers can enhance user experience and maintain data integrity in their Flutter applications.