Solving the Vertical Viewport Unbounded Height Error in Flutter: Nested Scroll View Explained

Learn how to fix the common Flutter error of vertical viewport being given unbounded height when nesting a horizontal ListView inside a Nested Scroll View.
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This video is based on the question https://stackoverflow.com/q/72067349/ asked by the user 'Deogratius Mabima' ( https://stackoverflow.com/u/17690810/ ) and on the answer https://stackoverflow.com/a/72067643/ provided by the user 'Mohamed Nagdy' ( https://stackoverflow.com/u/12131813/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Solving the Vertical Viewport Unbounded Height Error in Flutter: Nested Scroll View Explained

When developing Flutter applications, it's common to run into issues when dealing with complex layouts. One frequent problem developers encounter is trying to nest horizontal ListViews inside a NestedScrollView, which results in an error stating "Vertical viewport was given unbounded height." If you're facing this problem, you're not alone. Let’s break down the situation and provide a clear solution to help you overcome this hurdle.

Understanding the Problem

The Flutter framework is built with a tree of widgets that can sometimes lead to issues with layout dimensions—especially when mixing vertical and horizontal scrolling views. The error message you might encounter, "Vertical viewport was given unbounded height," typically arises when a widget, such as a ListView, is trying to determine its height but doesn't receive any constraints for that size.

Why This Error Occurs

In scenarios where a ListView is placed directly inside of a Column (which can have an infinite height by default), without any constraints set for its size, Flutter becomes confused about how to properly render this widget. Therefore, it's crucial to provide clear constraints to ensure that the layout behaves as expected.

The Solution: Using SizedBox or Expanded

To resolve the unbounded height error, you can wrap your ListView with either a SizedBox or Expanded widget, which will provide it with a definite height and allow your layout to function correctly.

Option 1: Using SizedBox

The SizedBox widget can be used to give a specific height to the ListView. Here’s how you can implement it in your code:

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

Option 2: Using Expanded

Alternatively, if you want the ListView to take up all available space within its parent, you can opt for the Expanded widget:

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

Conclusion

By wrapping your ListView with either SizedBox or Expanded, you effectively provide the necessary constraints to avoid the unbounded height issue. This modification not only resolves the error but also ensures that your layout remains flexible and user-friendly. Now, you can nest horizontal lists inside vertical lists with ease, enhancing the overall user experience of your Flutter application.

If you continue to encounter issues or have other questions related to Flutter development, feel free to reach out or leave a comment below. Happy coding!

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