How to Center a View in NestedScrollView on Android using Kotlin

Learn how to effectively center a view within a `NestedScrollView` on Android using Kotlin, even when dealing with nested layouts.
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This video is based on the question https://stackoverflow.com/q/70243268/ asked by the user 'Astrit Veliu' ( https://stackoverflow.com/u/5562702/ ) and on the answer https://stackoverflow.com/a/70332187/ provided by the user 'Muhannad Fakhouri' ( https://stackoverflow.com/u/4226162/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Centering a View in NestedScrollView: A Practical Guide for Android Developers

When developing complex layouts in Android, it's not uncommon to encounter problems with scrolling views, especially when dealing with nested layouts. A frequently asked question among developers is how to scroll a view to the center of a NestedScrollView when that view is part of a hierarchy of other layouts. This guide aims to clarify this problem and offer a suitable solution.

Understanding the Issue

In cases where you dynamically generate views based on responses, it can often be challenging to bring a specific view into focus—particularly if it's nested within several other layouts. Here’s a typical scenario you might face:

You have a hierarchy of layouts that include a NestedScrollView, a ConstraintLayout, and other views.

You attempt to position a specific view at the center of the screen upon certain actions, but the scrolling might not function as expected, leaving the view out of place.

The usual scrolling methods, like smoothScrollTo, may not always yield the desired results due to the nature of the view hierarchy.

A Step-by-Step Solution

To effectively scroll to and center a view within a NestedScrollView, you can implement the following approach using Kotlin. The key is to calculate the view's position relative to its parent.

Step 1: Calculate the Position of the Target View

The first step is to determine the top position of the view in relation to the NestedScrollView. You will need a function that aggregates this position correctly, considering all parent views:

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

Step 2: Use the Function in Your Code

Once you've defined the scrollTo extension function, use it where necessary in your code like this:

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

This simple call will now handle scrolling the NestedScrollView and correctly positioning your target view at the top, effectively centering it on the screen.

Why This Works

Hierarchy Calculation: The core of the solution lies in how the position is calculated within the view structure. The loop adds the top position of the target view, moving up the hierarchy until it reaches the ScrollView, ensuring the total distance to scroll is accurately computed.

Smooth User Experience: By using smoothScrollTo, you ensure that the scrolling action is user-friendly, providing a better experience as it adjusts the view's position gradually.

Conclusion

Scrolling a view to the center of a NestedScrollView can be tricky when dealing with complex layouts. However, by correctly summing the positions of the view in relation to its parents, you can achieve precise control over its placement on the screen.

Feel free to implement this method in your projects, and don't hesitate to explore and tweak it further to fit your specific use cases. Happy coding!

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