如何在UIViewController之间使用自定义转场动画

要在UIViewController之间使用自定义转场动画，可以遵循以下步骤：

1. 创建一个实现了UIViewControllerAnimatedTransitioning协议的自定义转场动画类。这个类需要实现两个方法：transitionDuration和animateTransition。

class CustomTransitionAnimator: NSObject, UIViewControllerAnimatedTransitioning {
    
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.5
    }
    
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        // 实现自定义动画逻辑
    }
}

2. 在你的UIViewController中设置转场代理，并实现UIViewControllerTransitioningDelegate协议中的方法。

class FirstViewController: UIViewController, UIViewControllerTransitioningDelegate {
    
    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        let secondViewController = segue.destination as! SecondViewController
        secondViewController.transitioningDelegate = self
    }
    
    // 实现UIViewControllerTransitioningDelegate协议方法
    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return CustomTransitionAnimator()
    }
    
    func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return CustomTransitionAnimator()
    }
}

3. 在你的CustomTransitionAnimator类中实现animateTransition方法，定义具体的动画逻辑。

func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
    let containerView = transitionContext.containerView
    let fromView = transitionContext.view(forKey: .from)!
    let toView = transitionContext.view(forKey: .to)!
    
    // 实现自定义动画逻辑
    // 将动画效果添加到containerView中
    
    // 动画完成后需要调用completeTransition方法
    transitionContext.completeTransition(true)
}

通过以上步骤，你就可以在UIViewController之间使用自定义转场动画了。在进行转场时，系统会自动调用你实现的自定义转场动画类中的动画逻辑。