iOS-转场动画

学习及实践笔记

记录iOS中常见Modal、Push转场动画的学习及实践

相关api的记录及介绍

喵神文章传送门

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/*这个接口用来提供切换上下文给开发者使用,包含了从哪个VC到哪个VC等各类信息*/
@protocol UIViewControllerContextTransitioning
-(UIView *)containerView; VC切换所发生的view容器,开发者应该将切出的view移除,将切入的view加入到该view容器中。
-(UIViewController *)viewControllerForKey:(NSString *)key; 提供一个key,返回对应的VC。现在的SDK中key的选择只有UITransitionContextFromViewControllerKey和UITransitionContextToViewControllerKey两种,分别表示将要切出和切入的VC。
-(CGRect)initialFrameForViewController:(UIViewController *)vc; 某个VC的初始位置,可以用来做动画的计算。
-(CGRect)finalFrameForViewController:(UIViewController *)vc; 与上面的方法对应,得到切换结束时某个VC应在的frame。
-(void)completeTransition:(BOOL)didComplete; 向这个context报告切换已经完成。
/* 自定义转场动画中使用 */
/*这个接口负责切换的具体内容,也即“切换中应该发生什么”。开发者在做自定义切换效果时大部分代码会是用来实现这个接口*/
@protocol UIViewControllerAnimatedTransitioning
-(NSTimeInterval)transitionDuration:(id < UIViewControllerContextTransitioning >)transitionContext; 系统给出一个切换上下文,我们根据上下文环境返回这个切换所需要的花费时间
-(void)animateTransition:(id < UIViewControllerContextTransitioning >)transitionContext; 在进行切换的时候将调用该方法,我们对于切换时的UIView的设置和动画都在这个方法中完成。
/* ViewController中调用 */
@protocol UIViewControllerTransitioningDelegate
// 动画
-(id< UIViewControllerAnimatedTransitioning >)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source;
-(id< UIViewControllerAnimatedTransitioning >)animationControllerForDismissedController:(UIViewController *)dismissed;
// 交互
-(id< UIViewControllerInteractiveTransitioning >)interactionControllerForPresentation:(id < UIViewControllerAnimatedTransitioning >)animator;
-(id< UIViewControllerInteractiveTransitioning >)interactionControllerForDismissal:(id < UIViewControllerAnimatedTransitioning >)animator;
/* UIViewControllerInteractiveTransitioning 提供百分比控制交互切换*/
-(Float)completionSpeed 返回速度 1 - self.percentComplete;
-(void)updateInteractiveTransition:(CGFloat)percentComplete 更新百分比,一般通过手势识别的长度之类的来计算一个值,然后进行更新。之后的例子里会看到详细的用法
-(void)cancelInteractiveTransition 报告交互取消,返回切换前的状态
–(void)finishInteractiveTransition 报告交互完成,更新到切换后的状态

  • 注意点
    locationInView:获取到的是手指点击屏幕实时的坐标点;
    translationInView:获取到的是手指移动后,在相对坐标中的偏移量

注意:当我们在被modal出的控制器中,向self发送dismissViewController的方法时,这个消息,会被直接转发到显示它的VC中去

Present

BouncePresentTransition的具体实现

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#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
@interface SPBouncePresentTransition : NSObject<UIViewControllerAnimatedTransitioning>
@end

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#import "SPBouncePresentTransition.h"
@implementation SPBouncePresentTransition
- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext{
return 0.8f;
}
- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext{
// 获取相关ViewController
UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
// UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
CGRect bounds = [UIScreen mainScreen].bounds;
// 设置被modal出界面view的frame
CGRect finalFrame = [transitionContext finalFrameForViewController:toVC];
// 设置目标界面frame的offset,即初始位置
toVC.view.frame = CGRectOffset(finalFrame, 0, bounds.size.height);
// 取出containerView,将目标vc的view进行添加
UIView *containerView = [transitionContext containerView];
[containerView addSubview:toVC.view];
// 设置view的frame动画效果
[UIView animateWithDuration:[self transitionDuration:transitionContext] delay:0.0 usingSpringWithDamping:0.6 initialSpringVelocity:0.0 options:UIViewAnimationOptionCurveLinear animations:^{
toVC.view.frame = finalFrame;
} completion:^(BOOL finished) {
// 提交transion完成
[transitionContext completeTransition:YES];
}];
}
@end

在viewcontroller中如何使用

1.遵守UIViewControllerTransitioningDelegate协议
2.设置modal的vc的transitioningDelegate属性
3.实现代理方法

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-(id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source

具体可参照如下代码

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#pragma mark - Transition
- (void)testForModalTransition{
SPModalViewController *vc = [[SPModalViewController alloc] init];
vc.transitioningDelegate = self;// 设置代理
vc.dismissAction = ^{
[self dismissViewControllerAnimated:YES completion:nil];
};
[self presentViewController:vc animated:YES completion:nil];
}
// 代理方法
// init
/* self.bouncePresent = [[SPBouncePresentTransition alloc]init]; */
-(id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source{
return self.bouncePresent;
}

效果如下

animateTransition.gif

Dismiss

滑动效果的转场实现
需要注意的是,务必同时实现两个代理方法
触发顺序,为动画类->交互类,系统会优先处理animationControllerForDismissedController方法,如果有,则dismiss操作均为自定义dismissTransition(demo中的transitionDuration已经设置为1.5s,效果可如gif动图所示),如果没有设置,那么则为系统的dismiss动画。

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// 动画类
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed

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// 交互类
- (id<UIViewControllerInteractiveTransitioning>)interactionControllerForDismissal:(id<UIViewControllerAnimatedTransitioning>)animator

具体可参照如下代码

1.NormalDismiss

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#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
@interface SPNormalDismissTransition : NSObject<UIViewControllerAnimatedTransitioning>
@end

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#import "SPNormalDismissTransition.h"
@implementation SPNormalDismissTransition
- (NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext{
return 1.5f;
}
- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext{
UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
CGRect initialFrame = [transitionContext initialFrameForViewController:fromVC];
CGRect finalFrame = CGRectOffset(initialFrame, 0, [UIScreen mainScreen].bounds.size.height);
UIView *containerView = [transitionContext containerView];// 承载当前活动vc的view的containerView
[containerView addSubview:toVC.view];
[containerView sendSubviewToBack:toVC.view];// 将视图置于下层
[UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
fromVC.view.frame = finalFrame;
} completion:^(BOOL finished) {
[transitionContext completeTransition:![transitionContext transitionWasCancelled]];
}];
}
@end

2.SwipeTransition

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#import <UIKit/UIKit.h>
@interface SPPercentSwipeTransition : UIPercentDrivenInteractiveTransition
@property (nonatomic, assign) BOOL interacting;// 用来判断是否处理交互
- (void)addSwipeTransition2viewController:(UIViewController *)viewController;// 传入要添加panRecognizer的viewController
@end

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#import "SPPercentSwipeTransition.h"
@interface SPPercentSwipeTransition()
@property (nonatomic, weak) UIViewController *presenedController;// 当前被modal出的控制器 注意weak的使用,强引用造成无法释放
@property (nonatomic, assign) BOOL canEndTransition;// 当超过屏幕高度的1/4时,我们认为交互可以结束
@end
@implementation SPPercentSwipeTransition
- (void)addSwipeTransition2viewController:(UIViewController *)viewController{
self.presenedController = viewController;
[self addRecognizer2View:viewController.view];
}
- (void)addRecognizer2View:(UIView *)view{
UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] init];
[view addGestureRecognizer:pan];
[pan addTarget:self action:@selector(handleRecognizer:)];
}
- (void)handleRecognizer:(UIPanGestureRecognizer *)recognizer{
CGRect screenBounds = [UIScreen mainScreen].bounds;
CGPoint point = [recognizer translationInView:recognizer.view.superview];// translationInView
switch (recognizer.state) {
case UIGestureRecognizerStateBegan:
self.interacting = YES;
[self.presentingController dismissViewControllerAnimated:YES completion:nil];
break;
case UIGestureRecognizerStateChanged:
{
CGFloat actionPoint = point.y/(screenBounds.size.height /2);// 有效距离为屏幕高度的一半
actionPoint = fminf(fmaxf(actionPoint, 0.0), 1.0);
self.canEndTransition = actionPoint > 0.5;// 滑动超过屏幕高度的1/4则可完成转场
[self updateInteractiveTransition:actionPoint];
}
break;
case UIGestureRecognizerStateEnded:
case UIGestureRecognizerStateCancelled:
{
self.interacting = NO;
if (self.canEndTransition)
{
[self finishInteractiveTransition];
}
else if (!self.canEndTransition || recognizer.state == UIGestureRecognizerStateCancelled)
{
[self cancelInteractiveTransition];
}
}
break;
default:
break;
}
}
- (CGFloat)completionSpeed{// 返回转场的速度
return 1 - self.percentComplete;
}

效果如下

swipeTransition.gif

SemiModal

实现一个常见的semi半挂式modal,将我们上述的AnimationTransition(present)、NormalDismiss部分稍作处理即可
效果如下:

semiModal.gif

首先分析实现思路:
1.semi部分,在bouncePresentTransition中的toVC的view进行圆角处理,同时设置它在containerView中的frame为目标样式
2.背景部分,将当前fromVC的view进行截图,添加到转场容器containerView中,然后改变它的transform中的scale属性,进行等比例缩放,同时将底层viewController的view进行隐藏处理
3.因为上文中,我们已经处理了基于UIPercentDrivenInteractiveTransitionswipeTransition,所以不需要再关心百分比变化
4.上文中处理的normalDismiss,只是简单的对视图进行了切换,因为考虑到semi的样式会对底层viewController的view进行隐藏处理,所以我们需要特别注意,在transition完成时,要将目标vc的view显示出来

思路有了,那么接下来就是实现,具体请看代码:

截图方法

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- (UIImage *)getSnapShotFromView:(UIView *)view{
CGRect rect = view.bounds;
UIGraphicsBeginImageContextWithOptions(rect.size, false, 0);
[view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *snapShot = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return snapShot;
}

改造的bouncePresent

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- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext{
// 获取相关ViewController
UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
CGRect bounds = [UIScreen mainScreen].bounds;
// 设置被modal出界面view的frame
// CGRect finalFrame = [transitionContext finalFrameForViewController:toVC];
// -- semi效果 --
CGRect finalFrame = CGRectMake(0, bounds.size.height/3, bounds.size.width, bounds.size.height);
// 设置目标界面frame的offset,即初始位置
toVC.view.frame = CGRectOffset(finalFrame, 0, bounds.size.height);
// -- semi效果 --
toVC.view.layer.cornerRadius = 15;
[toVC.view.layer masksToBounds];
UIImageView *snapView = [[UIImageView alloc] initWithImage:[self getSnapShotFromView:fromVC.view]];
snapView.frame = fromVC.view.bounds;
snapView.tag = 404;//标记一下
// 将fromvc的view隐藏掉
fromVC.view.hidden = YES;
// 取出containerView(视图管理容器),将目标vc的view进行添加
UIView *containerView = [transitionContext containerView];
// -- semi效果 --
[containerView addSubview:snapView];
// 注意添加顺序
[containerView addSubview:toVC.view];
// 设置view的frame动画效果
[UIView animateWithDuration:[self transitionDuration:transitionContext] delay:0.0 usingSpringWithDamping:0.6 initialSpringVelocity:0.0 options:UIViewAnimationOptionCurveLinear animations:^{
toVC.view.frame = finalFrame;
snapView.transform = CGAffineTransformMakeScale(0.85, 0.85);
} completion:^(BOOL finished) {
// 提交transion完成
if ([transitionContext transitionWasCancelled]) {
[transitionContext completeTransition:NO];
[snapView removeFromSuperview];
fromVC.view.hidden = NO; // 注意隐藏操作
}else{
[transitionContext completeTransition:YES];
}
}];
}

改造的normalDismiss

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- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext{
UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
CGRect initialFrame = [transitionContext initialFrameForViewController:fromVC];
CGRect finalFrame = CGRectOffset(initialFrame, 0, [UIScreen mainScreen].bounds.size.height);
UIView *containerView = [transitionContext containerView];// 承载当transitionview的containerView
UIView *snapView = nil;// 取出截图 tag = 404
for (UIView *sub in containerView.subviews) {
if (sub.tag == 404) {
snapView = sub;
break;
}
}
[containerView addSubview:toVC.view];
[containerView sendSubviewToBack:toVC.view];// 将视图置于下层
[UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
fromVC.view.frame = finalFrame;
snapView.transform = CGAffineTransformIdentity;
} completion:^(BOOL finished) {
BOOL transitionComplete = ![transitionContext transitionWasCancelled];
[transitionContext completeTransition:transitionComplete];
if (transitionComplete) {
toVC.view.hidden = NO;
[snapView removeFromSuperview];
}else{
toVC.view.hidden = YES;
}
}];
}


Push&Pop

Push

在viewcontroller中如何使用

1.遵守UINavigationControllerDelegate协议
2.设置viewcontroller.navigationController.delegate的代理
3.实现代理方法

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- (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC

这里需要特别注意一点,对于Push和Pop,都会在此方法中返回,需要我们对operation进行类型判断,返回正确类型的自定义transition
同时要考虑一种特殊情况,就是自己并非第一层viewController时,从自身pop出去的情况

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if (fromVC == self && operation == UINavigationControllerOperationPop)
{// 从自己pop出去
return nil;
}

(我们可以发现,Push同上文中提到的Modal的处理方式一致,只是遵守的协议不同)

先看效果

transPush.gif

分析一下思路:
1.将点击的Cell中的imageView,传入到转场容器container中,转换其坐标、截图并添加(注意同toVC.view的添加顺序),我们命名为snapView
2.获取fromVC中的目标图片位置,设置为snapview的终点frame

大概看一下我们如何实现,写一下几个比较关键的地方

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// 1.fromVC,处理点击CollectionView的点击事件
- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath{
PushCell *cell = (PushCell *)[collectionView cellForItemAtIndexPath:indexPath];
self.transImgView = cell.transImg;
SPGakkiViewController *gakki = [[SPGakkiViewController alloc] init];
[self.navigationController pushViewController:gakki animated:YES];
}
// 2.transition中的写法
SPGakkiViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
SPPushViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
// 获取视图容器
UIView *containerView = [transitionContext containerView];
// 获取需要变换的视图
UIImageView *transImgView = fromVC.transImgView;
UIView *snapView = [transImgView snapshotViewAfterScreenUpdates:NO];
snapView.frame = [transImgView convertRect:transImgView.bounds toView:containerView];
// 先隐藏视图
toVC.showContent = NO;
[containerView addSubview:toVC.view];
[containerView addSubview:snapView];
// 动画部分
[UIView animateWithDuration:[self transitionDuration:transitionContext] delay:0 usingSpringWithDamping:0.6 initialSpringVelocity:1/0.6 options:UIViewAnimationOptionCurveEaseInOut animations:^{
snapView.frame = toVC.targetFrame;
} completion:^(BOOL finished) {
snapView.hidden = YES;
toVC.showContent = YES;
[snapView removeFromSuperview];
[transitionContext completeTransition:![transitionContext transitionWasCancelled]];
}];
Pop

效果如下

transPop.gif

如果一路写到这里,想必已经明白转场动画的基本使用,所以我们不再赘述,只附效果的实现代码

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SPPushViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
SPGakkiViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
// 获取视图容器
UIView *containerView = [transitionContext containerView];
[containerView addSubview:toVC.view];
toVC.view.alpha = 0;
// 截图
UIView *snapView = [fromVC.imageView snapshotViewAfterScreenUpdates:NO];
// 隐藏
fromVC.showContent = NO;
// 目标位置
CGRect startFrame = fromVC.targetFrame;
CGRect targetFrame = [toVC.transImgView convertRect:toVC.transImgView.bounds toView:containerView];
snapView.frame = startFrame;
[containerView addSubview:snapView];
// 开始动画
[UIView animateWithDuration:[self transitionDuration:transitionContext] delay:0 usingSpringWithDamping:0.6 initialSpringVelocity:1/0.6 options:UIViewAnimationOptionCurveEaseInOut animations:^{
snapView.frame = targetFrame;
snapView.alpha = 0;
toVC.view.alpha = 1;
} completion:^(BOOL finished) {
snapView.hidden = YES;
[snapView removeFromSuperview];
[transitionContext completeTransition:![transitionContext transitionWasCancelled]];
}];

注意!注意!注意! [transitionContext completeTransition:![transitionContext transitionWasCancelled]];务必在动画结束时上报转场结束状态(此处手动鲜血红)

返回手势
只需要我们在之前写的percentSwipeTransition中稍加改造即可,我们将它稍加封装,代码如下

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#import <UIKit/UIKit.h>
typedef NS_ENUM(NSInteger,SPTransitionType) {
SPTransitionTypePush,
SPTransitionTypeModal
};
@interface SPPercentSwipeTransition : UIPercentDrivenInteractiveTransition
@property (nonatomic, assign) BOOL interacting;
- (void)addSwipeTransition2viewController:(UIViewController *)viewController withType:(SPTransitionType)type;
@end
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#import "SPPercentSwipeTransition.h"
@interface SPPercentSwipeTransition()
@property (nonatomic, weak) UIViewController *presentingController;
@property (nonatomic, assign) BOOL canEndTransition;
@property (nonatomic, assign) SPTransitionType currentType;
@end
@implementation SPPercentSwipeTransition
- (void)addSwipeTransition2viewController:(UIViewController *)viewController withType:(SPTransitionType)type{
self.currentType = type;
[self addSwipeTransition2viewController:viewController];
}
- (void)addSwipeTransition2viewController:(UIViewController *)viewController{
self.presentingController = viewController;
[self addRecognizer2View:viewController.view];
}
- (void)addRecognizer2View:(UIView *)view{
UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] init];
[view addGestureRecognizer:pan];
[pan addTarget:self action:@selector(handleRecognizer:)];
}
- (void)handleRecognizer:(UIPanGestureRecognizer *)recognizer{
switch (recognizer.state) {
case UIGestureRecognizerStateBegan:
self.interacting = YES;
[self moveBackWithTransitionType:_currentType];
break;
case UIGestureRecognizerStateChanged:
[self handleTransitionWithType:_currentType andRecognizer:recognizer];
break;
case UIGestureRecognizerStateEnded:
case UIGestureRecognizerStateCancelled:
{
self.interacting = NO;
if (self.canEndTransition)
{
[self finishInteractiveTransition];
}
else if (!self.canEndTransition || recognizer.state == UIGestureRecognizerStateCancelled)
{
[self cancelInteractiveTransition];
}
}
break;
default:
break;
}
}
- (void)moveBackWithTransitionType:(SPTransitionType)type{
switch (type) {
case SPTransitionTypeModal:
[self.presentingController dismissViewControllerAnimated:YES completion:nil];
break;
case SPTransitionTypePush:
[self.presentingController.navigationController popViewControllerAnimated:YES];
break;
}
}
- (void)handleTransitionWithType:(SPTransitionType)type andRecognizer:(UIPanGestureRecognizer *)recognizer{
CGRect screenBounds = [UIScreen mainScreen].bounds;
CGPoint point = [recognizer translationInView:recognizer.view.superview];// translationInView
switch (type) {
case SPTransitionTypePush:
{
CGFloat percent = point.x/(screenBounds.size.width /2);// 有效距离为屏幕宽度的一半
percent = fminf(fmax(percent, 0.0), 1.0);
self.canEndTransition = percent > 0.5;// 活动超过屏幕宽度的1/4则可完成转场
[self updateInteractiveTransition:percent];
}
break;
case SPTransitionTypeModal:
{
CGFloat actionPoint = point.y/(screenBounds.size.height /2);// 有效距离为屏幕高度的一半
actionPoint = fminf(fmaxf(actionPoint, 0.0), 1.0);
self.canEndTransition = actionPoint > 0.5;// 滑动超过屏幕高度的1/4则可完成转场
[self updateInteractiveTransition:actionPoint];
}
break;
}
}
- (CGFloat)completionSpeed{
return 1 - self.percentComplete;
}
@end

因为加入了手势处理,所以我们需要将Pop中上报转场完成的地方稍加改动
考虑手势取消转场的情况,取消时,将fromVC的内容再次显示即可

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// 开始动画
[UIView animateWithDuration:[self transitionDuration:transitionContext] delay:0 usingSpringWithDamping:0.6 initialSpringVelocity:1/0.6 options:UIViewAnimationOptionCurveEaseInOut animations:^{
snapView.frame = targetFrame;
snapView.alpha = 0;
toVC.view.alpha = 1;
} completion:^(BOOL finished) {
BOOL completeTransiton = ![transitionContext transitionWasCancelled];
snapView.hidden = YES;
if (!completeTransiton) fromVC.showContent = YES;
[snapView removeFromSuperview];
[transitionContext completeTransition:completeTransiton];
}];

看一下我们的最终效果

swipeTrans.gif


总结

1.理解ContainerView的作用
2.务必上报transition结束或取消状态
3.区分UIViewControllerTransitioningDelegateUINavigationControllerDelegate的使用场景
4.转场动画的关键,在于处理fromVC和toVC的view的变化,最终还是回归到UIView动画
5.体会自定义transition时,代理方法带来的简洁高效