Solving SwiftUI’s Strange systemImage Animation Behavior

Discover why your SwiftUI animations using `systemImages` may fail and how to fix them with effective strategies and solutions.
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This video is based on the question https://stackoverflow.com/q/70161049/ asked by the user 'John Sorensen' ( https://stackoverflow.com/u/15578536/ ) and on the answer https://stackoverflow.com/a/70162249/ provided by the user 'Yrb' ( https://stackoverflow.com/u/7129318/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding Animation Issues with SwiftUI System Images

If you're a SwiftUI enthusiast, you may have encountered unexpected behavior when animating elements that utilize systemImages. One of the most common issues arises when developers try to animate changes using Image(systemName: "circle"), resulting in cryptic error messages and frustrating "purple" warnings in Xcode. Here, we'll explore the problem in detail and provide a thorough solution to enhance your animation experience with SwiftUI.

The Problem When Animating SF Symbols

The issue starts when you attempt to animate the ExpandingCircleImage using the SF symbol. You may be surprised to find yourself confronted with an error message indicating that "No symbol named 'circle' found in system symbol set." This can occur due to several reasons:

You're attempting to use a font size of zero in your animations.

A timer driving the animation can cause inconsistencies and strange behaviors.

This raises the question: why does animating circles created using Circle() work flawlessly while Image(systemName: "circle") fails? The answer lies primarily in the method of animation and view state management associated with SwiftUI.

A Step-by-Step Solution

Let's break down the solution into manageable sections to ensure your animations using SF symbols are smooth and effective.

1. Managing Font Size

The first step to resolving the issue is to ensure that you never try to animate the font size to zero. When using Image(systemName: "circle"), animations rely heavily on the size of the image being greater than zero. To prevent this error, include checks to ensure that you don’t pass a size of zero.

2. Creating Animatable Modifiers

SwiftUI provides a flexible way to animate values through AnimatableModifiers. Here's how you can create one specifically to manage font size:

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In this modifier, the animatableData variable helps SwiftUI know which property to animate, specifically the size of the font.

3. Enhancing the Animation Logic

Transitioning from a single animation driven by a timer to a component that builds its animations internally will lead to better results. You can set it up like this:

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By using withAnimation inside onAppear, we allow the view to automatically manage its animation state.

4. Putting It All Together

With all the components established, you can now integrate the animated views seamlessly. Here is a snapshot of how you may structure your ContentView:

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Conclusion

To wrap things up, animating SF symbols in SwiftUI requires careful management of the size and using animatable modifiers effectively. By avoiding zero font sizes and redesigning your animations to rely on the view's internal states, you can create stunning and fluid animations using system images with ease.
Happy coding!