Solving ScrollController attached to multiple scroll views Issue in Flutter

Описание: Discover how to resolve the `ScrollController` issue in Flutter when using multiple scroll views within a Page View. Get step-by-step instructions to implement the solution effectively.
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This video is based on the question https://stackoverflow.com/q/70055906/ asked by the user 'Mohamed Ahmed' ( https://stackoverflow.com/u/14646078/ ) and on the answer https://stackoverflow.com/a/70061829/ provided by the user 'Mohamed Ahmed' ( https://stackoverflow.com/u/14646078/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Troubleshooting the ScrollController Attached to Multiple Scroll Views Issue in Flutter

If you’ve been developing a hybrid mobile application using Dart and Flutter, you might have encountered a puzzling error message: ScrollController attached to multiple scroll views. This issue often crops up when navigating between screens, particularly when using a PageView in conjunction with a TabBar. When trying to reinitialize the controller, developers frequently face disruptive assertions that hinder smooth scrolling and navigation. In this guide, we’ll delve into this problem and outline a structured solution.

Understanding the Problem

The error message stems from the Android UI framework, asserting that a ScrollController can only be attached to one ScrollView at a time. This can lead to complications like losing the state of a scrollable view or causing UI inconsistencies. Here’s the scenario:

You navigate from Screen A to a PageView Screen.

Upon closing and reopening the PageView Screen from a different Screen B, the controller is reinitialized leading to an error.

Specifically, you encounter an assertion failure at this line:

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

This is an indication that the previous instance of ScrollController wasn’t disposed of correctly.

Step-by-Step Solution

Fortunately, resolving this issue is straightforward once you understand the root cause. Below are the steps you can take to fix this error.

Step 1: Understand the Provider Class

In your provided code, you are using a PageViewProvider class to manage the state of the PageView. Here’s a breakdown of what the class is doing:

The PageController is created and initialized with a specific page index.

Your tab index is updated to reflect user interactions.

Step 2: Avoid Using Consumer Above PageView

The critical fix here is to avoid using Consumer above the PageView widget. This can lead to multiple instances of the ScrollController, which triggers the error you’re experiencing. Instead, access the PageController directly using the Provider context.

Here’s the revised code for accessing the PageController:

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

Step 3: Implementing the Change in Code

Remove the Consumer Widget: Remove the Consumer widget that surrounds your PageView widget.

Use Read Method: Access the pageViewController directly from the PageViewProvider using the context.

Here’s the updated structure for your PageView:

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

Step 4: Test the Application

Once you’ve made these adjustments, run your application. You should now be able to navigate back and forth between the screens without encountering the ScrollController error.

Conclusion

Bugs and errors with ScrollController in Flutter can be frustrating, especially when working with complex state management through providers. By ensuring that only one instance of ScrollController is being used and preventing multiple attachments, you can maintain a fluid experience in your app.

This solution illustrates how a simple adjustment in the way you access your controller can lead to significant improvements in functionality. Happy coding!