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Learn how to properly load data from a local file into your Flutter app's state ensuring the UI reflects the latest updates consistently, even after app restarts.
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This video is based on the question https://stackoverflow.com/q/74058043/ asked by the user 'Alex Galantsev' ( https://stackoverflow.com/u/20094013/ ) and on the answer https://stackoverflow.com/a/74061027/ provided by the user 'Ye Lwin Oo' ( https://stackoverflow.com/u/19209151/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Fix Data Not Updating in initState in Flutter Apps

If you are developing a Flutter application that involves loading data from a local file, you might run into issues where the data does not update properly within the initState() method. This can be particularly troublesome if you expect your UI to display the latest information stored on the device. In this guide, we'll explore a common problem faced by developers and walk through a comprehensive solution to ensure that your app effectively manages data persistence and updates without hiccups.

Understanding the Problem

You may have faced a scenario where you want to read data from a local file and use that data to populate your app’s UI. In the context of Flutter, this is typically done in a StatefulWidget’s lifecycle method called initState(). The challenge arises when you notice that the data is not available or loaded before your UI builds, leading to an inconsistency or incomplete rendering of your application.

For instance, in your case, you are running a function to read a JSON file asynchronously, but the information is being displayed only after the initial UI build, which is not the desired behavior.

Proposed Solution

Step 1: Utilizing FutureBuilder

Instead of directly accessing the data within the initState() method, you should utilize the FutureBuilder widget. This widget lets you work with asynchronous data directly in your UI, providing an elegant solution for dealing with loading, error, and success states.

Example Implementation of FutureBuilder

To implement this, modify your build method to include a FutureBuilder that waits for the data to be fetched before proceeding to render your layout:

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Step 2: Data Parsing Logic

You also need to ensure that the data retrieved from the file can be parsed and represented in your app properly. For that, introduce a method to process the retrieved JSON data accordingly. Here’s an example function that parses the JSON and updates the app’s state:

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Step 3: Ensuring Data Persistence

Make sure that when users make changes in your app (like adding nodes in your tree view), those changes are saved back to the local file. Implement write functions that effectively serialize your data back to the file system.

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Conclusion

In conclusion, by utilizing FutureBuilder to manage asynchronous data loading and ensuring proper handling and parsing of local files, you can maintain an update UI that seamlessly reflects users' modifications, even after restarting the app. If your issue was not just about fetching data but also about the overall game logic of resuming progress, consider implementing any necessary additional logic based on user actions and states accordingly.

This approach ensures that your Flutter application becomes more robust, user-friendly, and interactive, ultimately providing a better experience for your users. Happy coding!