Скачать или смотреть Solving the DropdownButton Value Display Issue in Flutter

Discover how to fix the issue of the `DropdownButton` not showing the selected value in Flutter. Follow our step-by-step guide to ensure smooth user interactions.
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This video is based on the question https://stackoverflow.com/q/74293224/ asked by the user 'user19976096' ( https://stackoverflow.com/u/19976096/ ) and on the answer https://stackoverflow.com/a/74293245/ provided by the user 'Md. Yeasin Sheikh' ( https://stackoverflow.com/u/10157127/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Solving the DropdownButton Value Display Issue in Flutter

When developing applications with Flutter, a common UI element is the DropdownButton. However, many developers encounter an issue where the selected value from the DropdownButton isn't displayed, even after proper selection. This guide will help you troubleshoot and solve the issue of the selected value not appearing in the text portion of the DropdownButton.

Understanding the Problem

In your Flutter application, you may have set up a DropdownButton like this:

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

Upon selecting a value from the dropdown, the message appears as expected in the console, but the selection does not show in the button itself. This can be frustrating, particularly if the component is a crucial part of your UI.

Symptoms

Dropdown shows the list of options correctly.

Selected value appears in the console when selected.

The selection does not show in the DropdownButton text.

The Solution

The key to resolving this issue lies in the placement of the variable that holds the selected value. Specifically, the currentSelectedValue variable needs to be properly scoped outside of the build method to ensure that it can be accessed and updated correctly within state changes.

Step-by-Step Guide

Declare the Variable Outside the Build Method:
The currentSelectedValue variable should be declared at the class level, not within the build method. This ensures the state is maintained properly when the build function is executed again.

Implement the Changes:
Here is how you might implement the corrected setup in your Flutter widget:

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

Explanation:

State Management: By placing currentSelectedValue outside of the build method, you’re ensuring that it retains its state across widget rebuilds. The setState call updates the variable, prompting Flutter to rebuild the widget with the new value.

Interaction Flow: When you select a new value, onChanged invokes setState, reflecting the change in the UI immediately.

Conclusion

By following the steps outlined above, you can resolve the issue of the selected value not appearing in the text portion of the DropdownButton in Flutter. This ensures a smooth user experience, enhancing the overall functionality of your application.

With just a small adjustment to how you manage the state of your DropdownButton, you can provide a more dynamic and interactive interface for users.

Happy coding with Flutter!