【Swift学习笔记-《PRODUCT》读书记录-实现自定义转场动画】

iOS默认的push动画是把即将展示的控制器从右边推过来。有时我们想实现类似PPT中的一些动画，这时候就需要自定义转场动画了。如下图我们想实现一个淡出并且放大的过场动画，在退出时是一个淡出缩小的动画。

首先需要自定义一个类DiaryAnimator.swift遵守 UIViewControllerAnimatedTransitioning 协议，然后实现它，代码如下：

import UIKit

class DiaryAnimator: NSObject, UIViewControllerAnimatedTransitioning {
    // 用于接受外界的operation
    var operation:UINavigationControllerOperation!
    
    // 返回动画时间
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.4
    }
    
    // 要设置的动画
    //UIKit calls this method when presenting or dismissing a view controller. Use this method to configure the animations associated with your custom transition. You can use view-based animations or Core Animation to configure your animations.
    

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        
        let containerview = transitionContext.containerView
        
        let fromVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.from)
        let fromView = fromVC!.view
        
        let toVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to)
        let toView = toVC?.view
        
        // 设置新场景透明度
        toView?.alpha = 0.0
        
        // 设置初始值
        if operation == UINavigationControllerOperation.pop {
            fromView?.transform = CGAffineTransform(scaleX: 1.0, y: 1.0)
        }else{
            toView?.transform = CGAffineTransform(scaleX: 0.3, y: 0.3)
        }
        
        containerview.insertSubview(toView!, aboveSubview: fromView!)
        
        UIView.animate(withDuration: transitionDuration(using: transitionContext), delay: 0, options: UIViewAnimationOptions.curveEaseInOut, animations: {
            if self.operation ==  UINavigationControllerOperation.pop {
                // 放大要转出的场景
                fromView?.transform = CGAffineTransform(scaleX: 3.3,y: 3.3)
            } else {
                // 设置新场景为原始大小
                toView?.transform = CGAffineTransform(scaleX: 1.0,y: 1.0)
            }
            
            toView?.alpha = 1.0
        },completion: { finished in
            transitionContext.completeTransition(true)
        })
    }
    
}

 自定义好动画后，在要使用的控制器中实现 UINavigationControllerDelegate 协议的 optional func navigationController(_ navigationController: UINavigationController, animationControllerFor operation: UINavigationControllerOperation, from fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? 方法，返回自定义的动画即可

extension HomeYearController : UINavigationControllerDelegate
{
    func navigationController(_ navigationController: UINavigationController, animationControllerFor operation: UINavigationControllerOperation, from fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        let animate = DiaryAnimator()
        animate.operation = operation
       return animate
    }
}