Скачать или смотреть Understanding the GeometryReader Behavior in SwiftUI: Solutions for Extracted Views

Discover why `GeometryReader` behaves differently when using extracted views in SwiftUI and learn effective solutions to center your content effortlessly.
---
This video is based on the question https://stackoverflow.com/q/63143836/ asked by the user 'thedp' ( https://stackoverflow.com/u/173623/ ) and on the answer https://stackoverflow.com/a/63146160/ 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: GeometryReader behaves oddly with an extracted view

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.
---
Understanding the GeometryReader Behavior in SwiftUI: Solutions for Extracted Views

When working with SwiftUI, you might encounter some unexpected behavior with the GeometryReader, especially when extracting views into separate components. This guide delves into a common issue where placing a Text view within a GeometryReader does not maintain its expected position when the text is moved to an extracted view.

The Problem

In the following example, the Text("hello") is correctly placed in the center of the screen when it is within the GeometryReader. The expected layout looks like this:

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

However, the scenario changes drastically when you move the Text into a separate extracted view. The Text view unexpectedly shifts to the top left corner:

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

This behavior leaves many developers questioning whether it is a bug or an intended feature of GeometryReader.

Understanding the Behavior

To clarify, this is not a bug. The observed behavior is due to how the GeometryReader operates in SwiftUI. It is important to remember that:

The GeometryReader does not function as a container that inherently aligns its contents. Instead, its primary role is to provide size and positioning information for custom alignment.

Solutions to the Issue

If you find yourself facing this issue with components extracted to separate views, consider implementing one of the following solutions:

Solution 1: Use Positioning

One way to solve this is by directly positioning your ExtractedView using the size information provided by GeometryReader. Here's how you can do it:

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

This code explicitly places the extracted view at the center coordinates of the parent GeometryReader, ensuring it appears where you expect.

Solution 2: Utilize a Stack Container

Another effective approach is to wrap the extracted view in a full-size stack container like VStack or HStack, which includes default alignment behavior. This method reliably centers the content:

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

By using frame(maxWidth: .infinity, maxHeight: .infinity), the stack expands to fill the available space within the GeometryReader, allowing the contents to be centered naturally.

Conclusion

Understanding the functionality of GeometryReader is crucial for effective layout management within SwiftUI. When extracting views, remember that GeometryReader does not provide built-in alignment, but with these solutions, you can easily work around the behavior to achieve the desired layout.

If you’re navigating the SwiftUI landscape, keep these tips in mind to ensure your UI components are positioned exactly as you intend!