Resolving the setState() or MarkNeedsBuild() Error in Your Flutter App

Discover how to fix the `setState() or markNeedsBuild()` error during build in your Flutter app and improve your settings widget's performance with our step-by-step guide.
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This video is based on the question https://stackoverflow.com/q/65539747/ asked by the user 'Demir' ( https://stackoverflow.com/u/11252174/ ) and on the answer https://stackoverflow.com/a/65539779/ provided by the user 'dm_tr' ( https://stackoverflow.com/u/14231239/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving the setState() or MarkNeedsBuild() Error in Your Flutter App

As a beginner in Flutter development, encountering errors can be both frustrating and discouraging. One such common issue is the setState() or MarkNeedsBuild() called during build error while trying to use widgets that rely on asynchronous data sources, like the StreamBuilder. If you are struggling with this problem in your app, you're not alone! In this post, we will break down the problem and provide a clear solution to help you overcome this hurdle.

Understanding the Problem

When developing a Flutter app, the setState() and MarkNeedsBuild() methods are crucial for updating the UI in response to changes in the app's state. However, you may encounter an error stating that setState() was called during the widget's build phase. This often happens when trying to update state with a method that is also being called within the build method itself, especially in widgets like StreamBuilder that rely on real-time data from sources like Cloud Firestore.

The Error Message

The error message looks something like this:

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

This indicates that the framework is not allowing changes during an ongoing build process, which can lead to flutter UI getting into an unstable state.

The Solution

Let's walk through the solution to this error step-by-step. The key change you need to make is to move the randomColor function outside of the build method and avoid calling setState in it since the variable is local.

Step 1: Move the randomColor Method

By removing the randomColor method from the build scope, you prevent the method from running every time the widget is built. Here’s how to modify it:

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

Step 2: Update Your Build Method

Now, keep your build method clean and free of any set state operations. You can simply call randomColor() without any issues.

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

Conclusion

By following the above steps, you should be able to resolve the setState() or MarkNeedsBuild() error in your Flutter app while maintaining the functionality of your StreamBuilder. Remember to keep your methods outside of the build function where possible and avoid unnecessary state updates during the build process.

Happy coding, and may your Flutter apps run smoothly! If you have any more questions about Flutter development, feel free to leave them in the comments below.

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