Скачать или смотреть How to Fix UIView Expansion Issues with Auto Layout in iOS

Facing issues with UIView expansion in your iOS app? Learn how to correctly use Auto Layout to fix your UIView expansion problems.
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This video is based on the question https://stackoverflow.com/q/76802571/ asked by the user '정재연' ( https://stackoverflow.com/u/13966540/ ) and on the answer https://stackoverflow.com/a/76802916/ provided by the user 'Al Mustakim' ( https://stackoverflow.com/u/11134035/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem: UIView Expansion Not Working Properly

When developing in iOS with Swift, one common challenge is managing the size and layout of custom views. For instance, if you have a custom UIView named UpperInformationUIView and you're trying to expand and collapse it based on various states (like default, shrunk, and expanded), you may encounter unexpected behavior where the view doesn't expand as intended. This issue can be quite frustrating, especially if the collapse function works perfectly but the expansion leads to a misalignment that seems to tug your view around before it stretches vertically.

The Code Snippet

Here's the code snippet provided for the expandView() function that is supposed to manage the view's expansion.

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The Issue Explained

The goal is for the UIView to expand downward from the current state to either maxHeight or defaultHeight, depending on its current state. However, many developers find that the center of the view moves downward first before the view takes up more vertical space. This can lead to a distracting transition that simply doesn’t feel right in your application.

The Solution: Adjusting the Superview Layout

The good news is that the solution to this issue is relatively straightforward! The root of the problem is a common oversight when dealing with Auto Layout. While your code structure is generally fine, the mistake lies in how you're updating the layout for your view.

Key Change to Implement

Instead of calling self.layoutIfNeeded(), you should adjust the layout of the view's superview. Here’s the change you need to make:

Replace the call to self.layoutIfNeeded() with self.superview?.layoutIfNeeded():

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This alteration ensures that the parent view (the superview) properly adjusts its layout according to changes made to its subviews, thus preventing any unexpected movement of the UIView’s center.

Final Thoughts

By implementing this small yet crucial change, your expandView() function should work seamlessly, and the UIView will expand as intended—without the unwanted vertical movement.

If after making this adjustment, you still face issues, don't hesitate to reach out for additional support. Understanding how Auto Layout constraints and superviews interact can often clear up many confusion points in iOS development.

Now, you can confidently expand and collapse your custom UIView, enhancing your app's user interface marvelously!