Скачать или смотреть Solving the TextField Value Passing Problem in Flutter

Learn how to properly pass values from a `TextField` onChanged event to display in a `Text` widget in Flutter. Discover common mistakes and best practices for managing state in your Flutter applications.
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This video is based on the question https://stackoverflow.com/q/59872834/ asked by the user 'Riyad Enakoua' ( https://stackoverflow.com/u/4298117/ ) and on the answer https://stackoverflow.com/a/67137047/ provided by the user 'Hafeezurrahman' ( https://stackoverflow.com/u/14114279/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the TextField onChanged Problem in Flutter

If you're a Flutter developer, you might have come across a common issue: you want to pass the value from a TextField using its onChanged event to a Text widget. This can often be a point of confusion, especially for those who are new to StatefulWidgets. In this post, we’ll dive into the typical pitfalls and provide a clear solution to ensure that your Text widget reflects the current value of the TextField as expected.

The Problem

A developer noted that they could print the value from the onChanged event correctly, but they had trouble displaying that value in a Text widget. Here's the essential part of their code:

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

In this scenario, the question arises: why doesn’t the Text widget update when the TextField value changes? This is primarily due to the scope of the variable name and how Flutter manages state.

The Solution

1. Declaring Variables Outside the Build Method

When using StatefulWidgets, it's essential to correctly manage where you declare your variables. In Flutter, when you want the UI to respond dynamically to changes, the variable must be declared at the class level (not inside the build method). Here’s the corrected structure:

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

2. StatelessWidget Considerations

If you’re working with StatelessWidgets, you will need to declare the variables globally to be accessible across the widget. Here’s an example:

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

3. Best Practices for State Management

Most of the time, developers utilize state management solutions like BLoC or Provider packages, which effectively handle state and minimize memory usage. Although the provided examples focus primarily on StatefulWidget, these best practices are instrumental in building scalable and maintainable applications.

Conclusion

By following these guidelines, you can successfully pass values from a TextField to a Text widget in Flutter. The key takeaway is to declare your variables properly and manage state efficiently. This approach not only fixes the immediate problem but also supports building robust Flutter applications. Happy coding!