iOS自定义转场动画

需求分析：

产品经理：我们的App页面切换时能不能不要总从右边把页面推出来啊
程序员：这个需要自定义转场动画...
产品经理：这个自定义转场难不难，不难就改改吧！
程序员：...

自定义转场动画实现逻辑

从iOS7开始，我们可以自定义转场动画了。转场动画主要还是分为两种：push和model，下面分别介绍实现方法。

自定义push转场动画

步骤：（以vc1 push到vc2为例）

1. 在vc1里需要实现UINavigationControllerDelegate的代理方法，该方法返回自定义动画对象就行了
2. 直接调用push方法就行了
3. 自定义动画实现（这个好像才是第一步）

直接贴代码了：

// 1. 在vc1里需要实现UINavigationControllerDelegate的代理方法
class VC1: UIViewController, UINavigationControllerDelegate

  // 自定义的push动画，后面介绍实现
    var pushAnimation = CustomAnimation()
    // MARK: - event response
    @IBAction func presentBtnClicked(_ sender: Any) {
       // 2. 直接调用push方法就行了，记得设置UINavigationControllerDelegate
        let vc = UIViewController()
        vc.view.backgroundColor = UIColor.lightGray
        navigationController?.delegate = self // 必须设置
        navigationController?.pushViewController(vc, animated: true)
    }
    
    // MARK: - UINavigationControllerDelegate
    func navigationController(_ navigationController: UINavigationController, animationControllerFor operation: UINavigationControllerOperation, from fromVC: UIViewController, to toVC: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return pushAnimation
    }

自定义动画类：

// 自定义动画类需要遵循UIViewControllerAnimatedTransitioning协议
class CustomAnimation: NSObject, UIViewControllerAnimatedTransitioning {
    
    // 返回动画持续时间
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.8
    }
    
    // 动画实现逻辑
    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {
        
        // 1. 从transitionContext获取目标视图控制器toVC
        let toVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to)
        
        // 2. 设置toVC的初始位置和最终位置
        let screenBounds = UIScreen.main.bounds
        let finalFrame = transitionContext.finalFrame(for: toVC!)
        toVC!.view.frame = screenBounds.offsetBy(dx: -screenBounds.size.width, dy: 0)
        
        // 3. 添加VC的view到containerView上
        let containerView = transitionContext.containerView
        containerView.addSubview(toVC!.view)
        
        // 4. 开始动画，下面调用了iOS7新加的一个弹性动画
        let duaration = transitionDuration(using: transitionContext)
        UIView.animate(withDuration: duaration,
                       delay: 0,
                       usingSpringWithDamping: 0.6,
                       initialSpringVelocity: 0,
                       options: UIViewAnimationOptions.curveLinear,
                       animations: { 
                       toVC!.view.frame = finalFrame
        }) { (_) in
            transitionContext.completeTransition(true)
        }
    }
}

自定义Model动画（present）

步骤：(以vc1 present到vc2为例)

1. vc1实现转场协议UIViewControllerTransitioningDelegate
2. 调用系统的present方法跳转即可
   代码：

// vc1需要遵循转场协议UIViewControllerTransitioningDelegate
class VC1: UIViewController, UIViewControllerTransitioningDelegate {

    // 自定义转场动画，这里还使用上面的自定义动画
    var presentAnimation = CustomAnimation()
    
    // MARK: - event response
    @IBAction func presentBtnClicked(_ sender: Any) {
        // 2. 调用系统的present方法跳转
        let vc = UIViewController()
        vc.view.backgroundColor = UIColor.lightGray
        vc.transitioningDelegate = self
        present(vc, animated: true, completion: nil)
    }
    
    // 1. vc1实现转场协议的方法
    // MARK: - UIViewControllerTransitioningDelegate
    func animationController(forPresented presented: UIViewController, presenting: UIViewController, source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
        return presentAnimation
    }