Solving SwiftUI List Focus Issues with -FocusState and Smooth Scrolling

Описание: Explore how to manage focus changes in SwiftUI Lists without sacrificing smooth scrolling. Learn techniques to improve performance and keep your user interface responsive.
---
This video is based on the question https://stackoverflow.com/q/73111917/ asked by the user 'Sergey' ( https://stackoverflow.com/u/703537/ ) and on the answer https://stackoverflow.com/a/73112743/ provided by the user 'Asperi' ( https://stackoverflow.com/u/12299030/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: SwiftUI List with -FocusState and focus change handling

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Smooth Scrolling in SwiftUI: Handling Focus State with List Views

Managing focus in SwiftUI applications can often be a challenge, especially when working with List views. One common problem developers face is ensuring that scrolling remains smooth while handling focus changes. If you've encountered constant rebuilding of the List during scrolling due to focus state changes, you're not alone. In this guide, we will explore a solution that alleviates these issues, allowing your List views to remain responsive while tracking focus effectively.

The Problem with Constant Rebuilding of List

As developers often encounter, attaching .onChanged(of: focus) to a List can trigger continuous rebuilding of the view, leading to choppy scrolling experiences. This issue occurs because each focus change essentially forces the List to redraw itself, making the UI less responsive and negatively impacting the user experience.

Key Observations

Choppy Scrolling: When using .onChanged(of: focus), smooth scrolling is disrupted.

List vs. ScrollView: Although replacing List with ScrollView resolves the issue, List offers essential features like sections and easy edit options that are hard to forgo.

Focus State Management: It’s crucial to manage the focus state without triggering unnecessary updates in the parent view of the List.

Finding a Solution: Utilizing Standalone Views

The optimal approach to this focus issue involves separating the list row content into standalone views. By keeping the FocusState internal to each row, we prevent the List from reacting to every focus change, leading to fewer updates and smoother scrolling.

Implementation Steps

Create a Standalone View for Each Row: This helps keep focus management localized and minimizes the impact on the parent List view.

Use a Binding Variable for Focus State: Update the focus state of the outer view based on changes within each row, but keep the internal state of focus management.

Here’s the code illustrating this approach:

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

Explanation of the Code

ContentView: This is the main view where the List is created. We define an enum Field to uniquely identify each text field.

ExtractedView: This struct represents a single row in the List, encapsulating its internal state, including the focus state.

Bindings: The inFocus variable is passed as a binding to keep track of which field is currently focused, but each row manages its FocusState separately.

Conclusion

By isolating the focus management to individual list items using standalone views, we can effectively prevent the constant rebuilding of the List during scrolling. This technique preserves the sleek look of your List, ensuring that users maintain a smooth experience when interacting with form elements. Implementing this method will not only improve performance but also make your SwiftUI application more user-friendly.

Happy coding, and may your scrolls be always smooth!