Animation Issue: SwiftUI View Not Animating Height Changes in UIHostingController

Hello,

I’m developing an app where I display a SwiftUI view inside a UIHostingController embedded within a UIKit ViewController. I’m trying to animate the height of the UIHostingController’s view based on a switch’s value, but the SwiftUI view doesn’t animate at all.

Below is a simplified version of my code:

class ViewController: UIViewController {
    
    private lazy var parentView: UIView = {
        let view = UIView()
        view.backgroundColor = .red
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()
    
    private lazy var hostingView: UIView = {
        let testView = TestView()
        let hostingController = UIHostingController(rootView: testView)
        let view = hostingController.view!
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()
    
    private lazy var button: UISwitch = {
        let button = UISwitch()
        button.addTarget(self, action: #selector(onClickSwitch(sender:)), for: .valueChanged)
        button.translatesAutoresizingMaskIntoConstraints = false
        return button
    }()
    
    private var hostingViewHeightConstraint: NSLayoutConstraint?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.addSubview(parentView)
        parentView.addSubview(hostingView)
        parentView.addSubview(button)
        
        NSLayoutConstraint.activate([
            parentView.topAnchor.constraint(equalTo: view.topAnchor),
            parentView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
            parentView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            parentView.trailingAnchor.constraint(equalTo: view.trailingAnchor)
        ])
        
        NSLayoutConstraint.activate([
            hostingView.bottomAnchor.constraint(equalTo: parentView.bottomAnchor),
            hostingView.leadingAnchor.constraint(equalTo: parentView.leadingAnchor),
            hostingView.trailingAnchor.constraint(equalTo: parentView.trailingAnchor)
        ])
        
        hostingViewHeightConstraint = hostingView.heightAnchor.constraint(equalTo: parentView.heightAnchor, multiplier: 0.5)
        hostingViewHeightConstraint?.isActive = true
        
        NSLayoutConstraint.activate([
            button.centerXAnchor.constraint(equalTo: parentView.centerXAnchor),
            NSLayoutConstraint(item: button,
                               attribute: .centerY,
                               relatedBy: .equal,
                               toItem: parentView,
                               attribute: .centerY,
                               multiplier: 0.25,
                               constant: 0)
        ])
    }
    
    @objc func onClickSwitch(sender: UISwitch) {
        hostingViewHeightConstraint?.isActive = false
        
        let multiplier: CGFloat = sender.isOn ? 0.25 : 0.5
        
        hostingViewHeightConstraint = hostingView.heightAnchor.constraint(equalTo: parentView.heightAnchor, multiplier: multiplier)
        hostingViewHeightConstraint?.isActive = true
        
        UIView.animate(withDuration: 0.3) {
            self.view.layoutIfNeeded()
        }
    }
}

I’m looking for the behavior demonstrated in the video below:

Does anyone have suggestions on how to achieve this?