Скачать или смотреть Fixing the non-null value must be returned Error in Flutter Apps

This guide explains how to resolve the `non-null value must be returned` error in Flutter applications, offering clear steps and code examples for developers.
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This video is based on the question https://stackoverflow.com/q/71364613/ asked by the user 'Aditi Mishra' ( https://stackoverflow.com/u/14061609/ ) and on the answer https://stackoverflow.com/a/71364656/ provided by the user 'Kantine' ( https://stackoverflow.com/u/11244991/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the non-null value must be returned Error in Flutter

If you’re a Flutter developer, you might have encountered the following error message while trying to run your app:

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

This error indicates that the Flutter framework expects a Widget to be returned from your build method, but for some reason, it ends up receiving null. In this guide, we'll dive into what causes this error and how you can fix it effectively.

The Problem

In the provided Flutter example, the build method does not have a return statement, which leads to the error. Here is the original code snippet:

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

What's Missing?

The problem arises because the build method is supposed to return a widget (in this case MaterialApp), but the code currently lacks a return statement. This results in Flutter being unable to properly identify what to show on the screen.

The Solution

To resolve the error, ensure that the build method returns the MaterialApp widget properly. Here’s how you can correct it:

Updated Code Example

The fixed version of the MyFlutterApp class is shown below:

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

Key Changes Made

Add a Return Statement: The key change made was adding a return before the MaterialApp widget.

Maintain Overall Structure: The underlying structure remains unchanged; we are still using a Scaffold with an AppBar and a Material widget.

Conclusion

In summary, the error message A non-null value must be returned since the return type 'Widget' doesn't allow null is a common stumbling block when developing with Flutter. The key takeaway is to ensure that your build method always returns a valid widget.

By following the adjustments mentioned above, you can avoid this issue and keep your Flutter applications running smoothly!

If you have further questions or run into more issues, feel free to leave a comment below!