Скачать или смотреть How to Fix the Error: The return type 'Future Null ' isn't a 'Widget' in Flutter

Learn how to resolve the Flutter error regarding the return type. Discover the proper use of Future and FutureBuilder to handle asynchronous tasks smoothly in your app.
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This video is based on the question https://stackoverflow.com/q/74967261/ asked by the user 'Ali Mustadji' ( https://stackoverflow.com/u/20891998/ ) and on the answer https://stackoverflow.com/a/74970223/ provided by the user 'krishnaacharyaa' ( https://stackoverflow.com/u/13431819/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Fix the Error: The return type 'Future<Null>' isn't a 'Widget' in Flutter

If you're developing a Flutter application, you might encounter the error message: "The return type 'Future Null ' isn't a 'Widget', as required by the closure's context." This typically arises when dealing with asynchronous functions that return Future types. In this guide, we'll dive into what causes this error and how to effectively resolve it.

Understanding the Problem

The problem comes up mainly when you're trying to use a Future within a widget context where a Widget is expected, such as in a builder or an onTap handler. Specifically, in your case, you're trying to call an asynchronous function deleteProduct, but the function is returning Future<Null>, which Flutter does not recognize as a valid Widget return type.

Error Breakdown

In the code snippet that caused the issue, you have something structured like this:

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

Here, Flutter expects the return value of the function you're calling to be a Widget, but instead, it gets a Future which leads to the error.

Solution to the Error

To fix this issue, you need to follow a two-step approach:

Step 1: Modify the Future Function

Change the return type of your deleteProduct function to return Future<Map<String, dynamic>> instead of Future<Null>. This allows you to return meaningful data from the API call.

Here’s how to adjust the code:

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

Step 2: Use FutureBuilder for Async Tasks

Next, you should use the FutureBuilder widget to handle the async operation properly and update the UI based on the results of the Future. Here’s how you can implement it:

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

Conclusion

By implementing the changes to your deleteProduct function and utilizing FutureBuilder, you can effectively manage async operations in your Flutter app and also avoid the error regarding return types that are not widgets. Always remember to ensure that your async function returns a suitable type that aligns with what your UI expects.

This approach not only resolves the current error, but it also enhances the overall robustness of your app when it comes to handling asynchronous data. Happy coding!