How to Implement an ExpansionPanelList in Flutter to Expand Individual Cards

Описание: Learn how to create an `ExpansionPanelList` in Flutter with a `ListView` builder that allows individual cards to expand when clicked, solving common issues faced by beginners in Flutter development.
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This video is based on the question https://stackoverflow.com/q/70603759/ asked by the user 'Awash' ( https://stackoverflow.com/u/14625059/ ) and on the answer https://stackoverflow.com/a/70604440/ provided by the user 'Bach' ( https://stackoverflow.com/u/10488444/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Mastering the ExpansionPanelList in Flutter: Opening Cards Individually

If you're new to Flutter development, you may have encountered challenges when working with components like the ExpansionPanelList. One common issue is that when you click to expand one card, all cards expand simultaneously. This can lead to a frustrating user interface and contradicts the very purpose of using expandable panels. In this guide, we'll tackle this problem and show you how to allow only the card you click on to expand.

The Problem at Hand

You have a code structure that successfully implements the ExpansionPanelList, but when you click on one of the cards, all of them expand. This behavior is not desirable as it creates a cluttered view and makes the UI less intuitive for users.

Example Scenario

Imagine a simple application where you want to display stories or articles. Each article is a card that, when clicked, reveals more information. In the original code structure, when a user clicks on any article, all articles would open simultaneously - clearly not the intended behavior.

The Solution: Individual Card Expansion

Step-by-Step Breakdown

Here’s how to modify your existing code to allow for the desired behavior:

1. Remove SingleChildScrollView

The first step in our solution is to remove the SingleChildScrollView that is being used as the child of the ListView. Since ListView.builder inherently supports scrolling, using SingleChildScrollView can lead to inefficient performance and can introduce complexity.

2. Separate State Management

Each ExpansionPanel should manage its own state. To do this, we will create a separate widget for each story, which includes its own _expanded variable. This essentially means that each card will control its own expansion state, preventing the need to refresh the entire screen whenever one is opened.

Updated Code Example

Here's how the optimized code looks:

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

Additional Best Practices

While this guide primarily focuses on fixing the expansion issue, here are a few tips that can help you enhance your implementation further:

Model Class for Stories: Instead of directly using Map objects for your stories, consider creating a model class. This practice will improve code readability and maintainability.

Decode JSON Data: If your stories come from a JSON source, use jsonDecode() to parse your stories cleanly into the model class.

Conclusion: A Better User Experience

By following these adjustments, each card in your ExpansionPanelList will expand independently when clicked, resulting in a much-improved user experience. Separating the state management into individual widgets not only solves the immediate problem but also prepares your codebase for future scalability.

With this newfound insight into managing Flutter's UI components effectively, you're one step closer to creating stunning and user-friendly applications.