iOS-自定义过渡动画没有反弹效果

如何解决iOS-自定义过渡动画没有反弹效果

我遵循了这个answer，但是在布局中使用了锚点。过渡本身很好，问题在于动画发生并且视图出现在屏幕上时，链接中没有像gif那样的反弹。我的动画只是从底部“出现”，而不是从底部过渡。这是非常突然的，而不是平稳的。

我没有像下面的代码那样使用UIView.Animate...，而是尝试了animate(withDuration:delay:usingSpringWithdamping:initialSpringVeLocity:options:animations:completion:)，但仍然没有跳动。

我在completionHandler中尝试了containerView.setNeedsUpdateConstraints()，containerView.layoutIfNeeded()，view.layoutIfNeeded()的不同组合，但使用了nada。我使用withDuration:从0.4到2.5进行游戏，但同样突然出现

实际的过渡效果很好，所以我在那里很好，只是它出现时没有反弹效果

class ViewController: UIViewController {
        
    init() {
        super.init(nibName: nil,bundle: nil)
        modalPresentationStyle = .custom
        transitioningDelegate = self
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    lazy var bgView: UIView = {
        let v = UIView()
        v.translatesAutoresizingMaskIntoConstraints = false
        v.backgroundColor = UIColor.black.withAlphaComponent(0.7)
        return v
    }()

    let anotherVC = AnotherController()
    
    var isPresenting = false
    let fullScreenHeight = UIScreen.main.bounds.height

    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .clear

        configureAnchors()

        let navVC = UINavigationController(rootViewController: anotherVC)
        addChildVCToParent(vc: navVC)
    }

    func addChildVCToParent(vc: UIViewController) {
        
        if (!vc.view.isDescendant(of: self.view)) {
            addChild(vc)
            vc.view.translatesAutoresizingMaskIntoConstraints = false
            view.addSubview(vc.view)
            vc.didMove(toParent: self)
            
            vc.view.topAnchor.constraint(equalTo: bgView.bottomAnchor).isActive = true
            vc.view.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor).isActive = true
            vc.view.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor).isActive = true
            vc.view.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor).isActive = true
        }
    }

    var bgViewHeightAnchor: NSLayoutConstraint?
    func configureAnchors() {
        
        view.addSubview(bgView)
        
        bgView.topAnchor.constraint(equalTo: view.topAnchor).isActive = true
        bgView.leadingAnchor.constraint(equalTo: view.leadingAnchor).isActive = true
        bgView.trailingAnchor.constraint(equalTo: view.trailingAnchor).isActive = true
        
        setBgViewHeightAnchorToFullScreenHeightAndAlphaToZero()
    }
    
    func setBgViewHeightAnchorToFullScreenHeightAndAlphaToZero() {
        
        bgView.alpha = 0
        
        bgViewHeightAnchor?.isActive = false
        bgViewHeightAnchor = bgView.heightAnchor.constraint(equalToConstant: fullScreenHeight)
        bgViewHeightAnchor?.isActive = true
    }
    
    func setBgHeightAnchorToOneFifthScreenHeightAndAlphaToOne() {
        
        bgView.alpha = 1
        
        bgViewHeightAnchor?.isActive = false
        bgViewHeightAnchor = bgView.heightAnchor.constraint(equalToConstant: fullScreenHeight / 5)
        bgViewHeightAnchor?.isActive = true
    }
}

extension ViewController: UIViewControllerTransitioningDelegate,UIViewControllerAnimatedTransitioning {
    
    func animationController(forPresented presented: UIViewController,presenting: UIViewController,source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return self
    }
    
    func animationController(fordismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return self
    }
    
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 1
    }
    
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        
        let containerView = transitionContext.containerView
        
        let toViewController = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to)
        guard let toVC = toViewController else { return }
        isPresenting = !isPresenting
        
        if isPresenting {

            containerView.addSubview(toVC.view)
            
            setBgViewHeightAnchorToFullScreenHeightAndAlphaToZero()
            
            // containerView.setNeedsUpdateConstraints()
            UIView.animate(withDuration: 0.4,delay: 0,options: [.curveEaSEOut],animations: {
                
                self.setBgViewHeightAnchorToOneFifthScreenHeightAndAlphaToOne()
                
                // containerView.layoutIfNeeded() // using this here ruins the entire animation
                // self.view.layoutIfNeeded()

            },completion: { (finished) in

                // containerView.layoutIfNeeded()
                // self.view.layoutIfNeeded()

                transitionContext.completeTransition(true)
            })

        } else {

            UIView.animate(withDuration: 0.4,animations: {

                self.setBgViewHeightAnchorToFullScreenHeightAndAlphaToZero()

            },completion: { (finished) in
                transitionContext.completeTransition(true)
            })
        }
    }
}