Скачать или смотреть Resolving the Scrollbar's ScrollController has no ScrollPosition attached Error in Flutter

Learn how to fix the common Flutter error related to ScrollControllers and Scrollbars by following our detailed guide.
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Understanding the Scrollbar's ScrollController has no ScrollPosition attached Error in Flutter

One common issue Flutter developers encounter is the error message: "The Scrollbar's ScrollController has no ScrollPosition attached." This error typically arises when you're trying to integrate a Scrollbar with a scrolling widget, such as SingleChildScrollView or ListView, without properly linking their respective ScrollControllers. Let’s break down the problem at hand and explore effective solutions to resolve this error.

The Problem

You might come across this error in scenarios where a Scrollbar is used in conjunction with a scrollable widget. Below is a snippet of code where the error may occur:

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

In this example, both the CustomScrollBar and the SingleChildScrollView utilize the same ScrollController. However, if the controller is not linked correctly to both widgets, you will trigger the aforementioned error.

Why the Error Occurs

The error indicates that the Scrollbar has not been provided with a proper ScrollPosition because it is not aware of the scrollable child it is supposed to track. This often happens when the ScrollController is either not implemented in one of the widgets or is incorrectly used.

Step-by-Step Solution

Here’s how you can resolve the scroll controller issue and ensure that the Scrollbar functions correctly with a scrolling widget:

1. Create a ScrollController

You need to establish a ScrollController that can be shared between the Scrollbar and the scrollable widget. Instantiate the controller like this:

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

2. Link the ScrollController to Both Widgets

Next, ensure that the same ScrollController is assigned to both the Scrollbar and the scrolling widget (like ListView or SingleChildScrollView):

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

3. Final Integration

Here’s how it would all work together in the widget tree you initially provided:

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

Just ensure that _scrollControllerForScrollBar is defined as a ScrollController and linked appropriately within both widgets.

Conclusion

By following these steps, you can effectively eliminate the Scrollbar's ScrollController has no ScrollPosition attached error in your Flutter project. Remember, proper linkage of ScrollController instances is essential when using scrollable widgets with a Scrollbar. This ensures that your UI not only runs smoothly but also provides a better user experience.

If you’re still facing issues even after linking the ScrollController, double-check your code for potential oversights. Happy coding!