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前言:
iOS默认的
presentViewController
的切换动画是从底部推入,消失是从顶部推出。但是,因为iOS系统默认的是适配所有转场上下文的。而针对特定的转场上下文,我们能做出更好的效果。
Tips:所谓的转场上下文,就是转场的开始View和结束View,以及对应的ViewController
目标效果
最终的效果
准备工作
首先写出一个CollectionView
,每个Cell是一个图片,由于本文的核心是如何转场,所以CollectionView
的部分略过。写完了之后,是这样的效果
点击某一个CollectionView Cell查看大图,再点击大图图片消失
这个最初的项目,可以在这里下载
如何实现自定义转场动画
iOS 8之后,我们可以通过设置
ViewController
的transitioningDelegate
来设置代理来处理转场动画。
通过文档,可以看到transitioningDelegate
是一个实现UIViewControllerTransitioningDelegate
协议的对象,先看看这个协议,本文主要利用以下两个方法
- animationControllerForDismissedController
- animationControllerForPresentedController
着两个方法的目的是,提供一个遵循UIViewControllerAnimatedTransitioning
协议的对象,然后又这个对象来实际处理专场。通过名字就可以看出来,一个是处理present一个是处理dismiss。
本文的设计是让ViewController
来处理转场,在didSelectItemAtIndexPath
中,设置pvc的转场代理
dvc.transitioningDelegate = self
然后,写一个extension来实现协议
extension ViewController:UIViewControllerTransitioningDelegate{
func animationControllerForDismissedController(dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
return nil
}
func animationControllerForPresentedController(presented: UIViewController, presentingController presenting: UIViewController, sourceController source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
return nil
}
}
这时候,再运行项目,会发现没有任何变化,还是默认的转场方式。因为我们还没有提供实际的动画 。当上述两个代理方法返回nil的时候,系统会使用默认的方式
实现UIViewControllerAnimatedTransitioning
新建一个文件,命名为Animator.swift,然后新建一个类,处理Present的转场(Dismiss类似),实现UIViewControllerAnimatedTransitioning协议
class PresentAnimator: NSObject,UIViewControllerAnimatedTransitioning{
}
这时候,会报错没有实现协议,然后,我们添加协议方法,这时候的Animator.swift如下
import Foundation
import UIKit
class PresentAnimator: NSObject,UIViewControllerAnimatedTransitioning{
let duration = 0.5 //动画的时间
var originFrame = CGRectZero //点击Cell的frame
func transitionDuration(transitionContext: UIViewControllerContextTransitioning?) -> NSTimeInterval {
return duration
}
func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
}
}
简单介绍下这里的协议方法
- transitionDuration,返回转场动画的时间
- animateTransition,进行实际的转场动画,通过参数transitionContext(转场上下文)来获取转场的fromView,toView,fromViewController,toViewController。
转场的原理
- 转场开始的时候,自动把FromView添加到转场ContainView
- 转场结束的时候,自动把FromView移除ContainView
所以,开发者要做的就是
- 把toView添加到转场ContainView中,并且定义好toView的初始位置和状态
- 定义好FromView和ToView的转场结束时候的状态
- 创建动画
实现实际的转场动画
基于上述的原理,我们修改实际的动画
func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
let containView = transitionContext.containerView()
let toView = transitionContext.viewForKey(UITransitionContextToViewKey)!
let finalFrame = toView.frame
let xScale = originFrame.size.width/toView.frame.size.width
let yScale = originFrame.size.height/toView.frame.size.height
toView.transform = CGAffineTransformMakeScale(xScale, yScale)
toView.center = CGPointMake(CGRectGetMidX(originFrame), CGRectGetMidY(originFrame))
containView?.addSubview(toView)
UIView.animateWithDuration(duration, animations: { () -> Void in
toView.center = CGPointMake(CGRectGetMidX(finalFrame), CGRectGetMidY(finalFrame))
toView.transform = CGAffineTransformIdentity
}) { (finished) -> Void in
transitionContext.completeTransition(true)
}
}
然后,在ViewController.swfit中,添加一属性
let presentAnimator = PresentAnimator()
修改didSelectItemAtIndexPath
override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
let dvc = DetailViewController()
dvc.image = UIImage(named: "image.jpg")
dvc.transitioningDelegate = self
let cell = collectionView.cellForItemAtIndexPath(indexPath) as! FullImageCell
presentAnimator.originFrame = cell.convertRect(cell.imageview.frame, toView: nil)
self.presentViewController(dvc, animated: true, completion: nil)
}
修改代理方法
func animationControllerForPresentedController(presented: UIViewController, presentingController presenting: UIViewController, sourceController source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
return presentAnimator
}
这时候的动画效果如Gif
同理,为dismiss添加转场动画
在Animator.swift中添加一个新的类
class DismisssAnimator:NSObject,UIViewControllerAnimatedTransitioning{
let duration = 0.6
var originFrame = CGRectZero
func transitionDuration(transitionContext: UIViewControllerContextTransitioning?) -> NSTimeInterval {
return duration
}
func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
let containView = transitionContext.containerView()
let toView = transitionContext.viewForKey(UITransitionContextToViewKey)! //Collection View
let fromView = transitionContext.viewForKey(UITransitionContextFromViewKey)! //全屏的imageview
let xScale = originFrame.size.width/toView.frame.size.width
let yScale = originFrame.size.height/toView.frame.size.height
containView?.addSubview(toView)
containView?.bringSubviewToFront(fromView)
UIView.animateWithDuration(duration, animations: { () -> Void in
fromView.center = CGPointMake(CGRectGetMidX(self.originFrame), CGRectGetMidY(self.originFrame))
fromView.transform = CGAffineTransformMakeScale(xScale, yScale)
}) { (finished) -> Void in
transitionContext.completeTransition(true)
}
}
}
然后,在ViewController.swift中didSelectItemAtIndexPath
设置presentAnimator.frame下一行添加
dismissAnimator.originFrame = cell.convertRect(cell.imageview.frame, toView: nil)
其中,dismissAnimator是ViewController的一个属性
let dismissAnimator = DismisssAnimator()
然后,在代理方法中,返回
func animationControllerForDismissedController(dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
return dismissAnimator;
}
最终的效果
完整工程的下载
CSDN下载(一会补上链接)