前两天做了一个过渡动画，为了防止忘记，在这记录一下如何做。
基本概念
UIViewControllerTransitioningDelegate
如图所示，其中绿色的表示from VC，蓝色的表示to VC，通过to VC的方法setTransitioningDelegate:来设置其过渡动画的代理，这个代理需要符合UIViewControllerTransitioningDelegate协议，这个协议提供了做动画需要的animator（这个可以是交互式动画，也可以是非交互式动画）和presentation controller。
Animator：主要做动画的部分都在这里实现，比如动画时间，怎么做等。非交互动画的animator需要遵守UIViewControllerAnimatedTransitioning协议；交互动画同时还要遵守UIViewControllerInteractiveTransitioning。你可以对present和dismiss分别提供相应的animator。
Presentation controller：modalPresentationStyle为UIModalPresentationCustom时，UIKit就会查找自定义的UIPresentationController，此时我们就可以提供一个自定义的来控制其形为；当modalPresentationStyle不为UIModalPresentationCustom时，系统会提供内部已经定义好的UIPresentationController。其作用在下面有说明。
Transitioning Contexts:定义了动画需要的一些元数据，比如动画涉及的VC等。 这些对象需要遵守 UIViewControllerContextTransitioning这个协议，一般来说，这个是由系统创建提供的。以参数形式提供给animator使用。
Transition Coordinators：提供了在做Transition动画的同时，做其它动画的功能，遵循 UIViewControllerTransitionCoordinator 协议。
present的调用顺序
UIKit调用animationControllerForPresentedController:presentingController:sourceController:得到animator,然后如图：
dismiss的调用顺序
UIKit调用 animationControllerForDismissedController: 得到animator,然后如图：
实现自定义Animator
得到动画参数
使用viewControllerForKey: 得到from VC、to VC。
使用containerView得到动画的“容器”。
使用viewForKey:得到要添加或删除的view。
使用finalFrameForViewController:得到VC的最终位置。
做动画
这里提供一个例子：
-(NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext {
return self.transitionDuration;
}
- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext {
// Get the set of relevant objects.
UIView *containerView = [transitionContext containerView];
UIViewController *fromVC = [transitionContext
viewControllerForKey:UITransitionContextFromViewControllerKey];
UIViewController *toVC = [transitionContext
viewControllerForKey:UITransitionContextToViewControllerKey];
UIView *toView = [transitionContext viewForKey:UITransitionContextToViewKey];
UIView *fromView = [transitionContext viewForKey:UITransitionContextFromViewKey];
// Set up some variables for the animation.
CGRect containerFrame = containerView.frame;
CGRect toViewStartFrame = [transitionContext initialFrameForViewController:toVC];
CGRect toViewFinalFrame = [transitionContext finalFrameForViewController:toVC];
CGRect fromViewFinalFrame = [transitionContext finalFrameForViewController:fromVC];
// Set up the animation parameters.
if (self.presenting) {
// Modify the frame of the presented view so that it starts
// offscreen at the lower-right corner of the container.
toViewStartFrame.origin.x = containerFrame.size.width;
toViewStartFrame.origin.y = containerFrame.size.height;
}
else {
// Modify the frame of the dismissed view so it ends in
// the lower-right corner of the container view.
fromViewFinalFrame = CGRectMake(containerFrame.size.width,
containerFrame.size.height,
toView.frame.size.width,
toView.frame.size.height);
}
// Always add the "to" view to the container.
// And it doesn't hurt to set its start frame.
[containerView addSubview:toView];
toView.frame = toViewStartFrame;
// Animate using the animator's own duration value.
[UIView animateWithDuration:[self transitionDuration:transitionContext]
animations:^{
if (self.presenting) {
// Move the presented view into position.
[toView setFrame:toViewFinalFrame];
}
else {
// Move the dismissed view offscreen.
[fromView setFrame:fromViewFinalFrame];
}
}
completion:^(BOOL finished){
BOOL success = ![transitionContext transitionWasCancelled];
// After a failed presentation
if ((self.presenting && !success)) {
[toView removeFromSuperview];
}
// Notify UIKit that the transition has finished
[transitionContext completeTransition:![transitionContext transitionWasCancelled]];
}];
}
- (void)animationEnded:(BOOL)transitionCompleted {
NSLog("transition end");
}
顺带一提，如果要实现一个交互式的animator，最简单的办法是使用一个UIPercentDrivenInteractiveTransition对象。
Presenting a View Controller Using Custom Animations
我们需要以下步骤：
- 创建要呈现的VC
- 创建自定义transitioning delegate对象，将它赋值给上述VC的
transitioningDelegateproperty - 调用
presentViewController:animated:completion:呈现上述VC
做transition动画的同时做其它动画
通过相应VC的transitionCoordinator属性得到这个Transition Coordinator，然后调用它的animateAlongsideTransition:completion: 或 animateAlongsideTransitionInView:animation:completion:来在transition的同时做其它动画的目的。
UIPresentationController
使用UIPresentationController可以达到下述目的：
- 设置presented view controller的大小
- 在动画时加入自定义的view
- 可以对加入的自定义的view做动画
- 适配
工作顺序
Presentation Controller在动画中的调用顺序如下图，dismiss时只是begin和end调用的函数分别换为dismissalTransitionWillBegin和dismissalTransitionDidEnd:。
定义自己的UIPresentationController
首先，我们应该考虑如下问题：
- 想加入何种view?
- 通过什么动画将view加到屏幕上？
- presented VC的最终大小？
- 屏幕转动时的动画？size 改变时的适配？
- 当动画做完时，presenting VC的view是否应该移除？
我们可以通过override frameOfPresentedViewInContainerView来控制presented VC的最终大小。
class SlideInPresentationController: UIPresentationController {
// MARK: - Properties
fileprivate var dimmingView: UIView!
private var direction: PresentationDirection
init(presentedViewController: UIViewController, presenting presentingViewController: UIViewController?, direction: PresentationDirection) {
self.direction = direction
super.init(presentedViewController: presentedViewController, presenting: presentingViewController)
setupDimmingView()
}
override func presentationTransitionWillBegin() {
containerView?.insertSubview(dimmingView, at: 0)
NSLayoutConstraint.activate(NSLayoutConstraint.constraints(withVisualFormat: "V:|[dimmingView]|", options: [], metrics: nil, views: ["dimmingView": dimmingView]))
NSLayoutConstraint.activate(NSLayoutConstraint.constraints(withVisualFormat: "H:|[dimmingView]|", options: [], metrics: nil, views: ["dimmingView": dimmingView]))
guard let coordinator = presentedViewController.transitionCoordinator else {
dimmingView.alpha = 1.0
return
}
coordinator.animate(alongsideTransition: { _ in
self.dimmingView.alpha = 1.0
}, completion: nil)
}
override func dismissalTransitionWillBegin() {
guard let coordinator = presentedViewController.transitionCoordinator else {
dimmingView.alpha = 0.0
return
}
coordinator.animate(alongsideTransition: { _ in
self.dimmingView.alpha = 0
}, completion: nil)
}
override func containerViewDidLayoutSubviews() {
presentedView?.frame = frameOfPresentedViewInContainerView
}
override var frameOfPresentedViewInContainerView: CGRect {
//1
var frame: CGRect = .zero
frame.size = size(forChildContentContainer: presentedViewController,
withParentContainerSize: containerView!.bounds.size)
//2
switch direction {
case .right:
frame.origin.x = containerView!.frame.width*(1.0/3.0)
case .bottom:
frame.origin.y = containerView!.frame.height*(1.0/3.0)
default:
frame.origin = .zero
}
return frame
}
override func size(forChildContentContainer container: UIContentContainer, withParentContainerSize parentSize: CGSize) -> CGSize {
switch direction {
case .left, .right:
return CGSize(width: parentSize.width*(2.0/3.0), height: parentSize.height)
default:
return CGSize(width: parentSize.width, height: parentSize.height*(2.0/3.0))
}
}
}
// MARK: - Private
private extension SlideInPresentationController {
func setupDimmingView() {
dimmingView = UIView()
dimmingView.translatesAutoresizingMaskIntoConstraints = false
dimmingView.backgroundColor = UIColor(white: 0.0, alpha: 0.5)
dimmingView.alpha = 0.0
let recognizer = UITapGestureRecognizer(target: self, action:#selector(handleTap(recognizer:)))
dimmingView.addGestureRecognizer(recognizer)
}
dynamic func handleTap(recognizer: UITapGestureRecognizer) {
presentingViewController.dismiss(animated: true)
}
}
//参考：<https://www.raywenderlich.com/139277/uipresentationcontroller-tutorial-getting-started>