swift-自定义转场动画模态控制器(不改变frame)

闲暇时间做转场动画(自定义不改变frame的转场动画)，demo类似如下所示：

自定义模态

只需要两步：

1. 自定义转场动画类
2. 设置转场代理

一, 自定义转场动画类

class CustomAnimation: NSObject {}

二, 设置转场代理

showVC.modalPresentationStyle = .custom // 背景视图不被删除

showVC.transitioningDelegate = customAnimation // 代理动画UIViewControllerTransitioningDelegate协议
// 其中，customAnimation 是一个懒加载属性，private lazy var customAnimation = CustomAnimation()

1，在自定义转场动画类CustomAnimation中，需要遵守UIViewControllerTransitioningDelegate协议：

//MARK: - 设置转场代理
extension CustomAnimation:UIViewControllerTransitioningDelegate{

func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
    // 弹出之后做事情  isPresent声明为私有变量即可
    isPresent = true
    return self
}


func animationController(forDismissed dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
// 消失之后做事情
    isPresent = false
    return self
}

}

2，由于上方法return self，所以需要遵守UIViewControllerAnimatedTransitioning协议

//MARK: - 自定义动画属性
extension CustomAnimation:UIViewControllerAnimatedTransitioning{

// 1 动画时长
func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
    return 0.5
}

// 2 设置点击之后是弹出 还是 消失
func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {

    isPresent ? animationPresentedView(transitionContext: transitionContext) : animationDismissedView(transitionContext: transitionContext)
    
}

func animationPresentedView(transitionContext: UIViewControllerContextTransitioning) {
    // 1 取出显示视图
    let presentView = transitionContext.view(forKey: .to)
    
    // 2 添加到containerView
    transitionContext.containerView.addSubview(presentView!);
    
    // 3 添加动画
    presentView?.alpha = 0.0
    UIView.animate(withDuration: transitionDuration(using: transitionContext), animations:         {
     presentView?.alpha = 1.0   

    }) { (_) in
        transitionContext.completeTransition(true)
    }
}


func animationDismissedView(transitionContext: UIViewControllerContextTransitioning) {
    // 1 取出消失视图
    let dismissView = transitionContext.view(forKey: .from)
  
    
    // 2 添加动画
    dismissView?.alpha = 1.0
    UIView.animate(withDuration: transitionDuration(using: transitionContext), animations:         {
        dismissView?.alpha = 0.0
    }) { (_) in
        
        transitionContext.completeTransition(true)
    }
}


}