Скачать или смотреть How to Retrieve the CGRect of a List View Item in SwiftUI

Discover how to effectively retrieve a `CGRect` for a list view item using `onLongPressGesture` in SwiftUI with a full implementation example.
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This video is based on the question https://stackoverflow.com/q/74574992/ asked by the user 'sash' ( https://stackoverflow.com/u/1757229/ ) and on the answer https://stackoverflow.com/a/74598002/ provided by the user 'sash' ( https://stackoverflow.com/u/1757229/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Retrieve the CGRect of a List View Item in SwiftUI

Developers often encounter challenges when they need to obtain rectangles of user interfaces in SwiftUI, especially when working with dynamic lists. If you've been wondering how to get the CGRect of a list view item when a user interacts with it (for instance, using onLongPressGesture), you're in the right place. In this guide, we will delve into a step-by-step solution that allows you to achieve precisely that.

The Problem

You may have a SwiftUI view structured somewhat like this:

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

In this code snippet, the goal is to retrieve the rectangle of each item in the LazyVStack when the item is pressed for a longer duration. Unfortunately, the direct approach will not work since SwiftUI does not store the frame information directly for list items.

The Solution

To effectively retrieve the CGRect, we can utilize SwiftUI's PreferenceKey. This allows us to share values up the view hierarchy. Here’s how to implement the solution step-by-step.

Step 1: Setting Up State to Store Frames

First, we need to declare a state variable to store the rectangles of our items:

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

Step 2: Creating the ContentView

This will house our scrollable list. Each item will retrieve its frame:

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

Step 3: Constructing the ItemView

This is the view for each item in the list. It simply displays the number and includes the necessary background geometry reader to calculate its frame:

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

Step 4: Implementing the PreferenceKey

This is where we define a custom PreferenceKey that will help collect the frame data:

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

Step 5: Creating the FrameModifier

Finally, the FrameModifier will provide the geometry information needed to calculate the rectangles of our list items:

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

Putting It All Together

With the steps above, you can retrieve the rectangles of your list items! This method provides a robust and reusable way to access frame information dynamically through user interactions.

Conclusion

Handling layouts and coordinating between user gestures and view dimensions in SwiftUI can initially seem complex. However, by leveraging tools like PreferenceKey and GeometryReader, you can create a responsive user interface that responds seamlessly to user interactions.

Feel free to use the provided code snippets in your projects to efficiently work with list view item rectangles in SwiftUI. Happy coding!