iOS 自定义转场动画浅谈

> 路漫漫其修远兮，吾将上下而求索

![kaipingtu.gif](/contentImages/image/jianshu/2525768-3de3520ec46cfa0a.gif)

#### 前记

想研究自定义转场动画很久了，时间就像海绵，挤一挤还是有的，花了差不多有10天的时间，终于对转场动画了解了一点。自从`iOS 7`以后，我们就可以自定义转场动画，实现我们想要的效果，在这之前，我们先来看一张图，大概了解下，需要知道些什么

`相关类联系图`

![Paste_Image.png](/contentImages/image/jianshu/2525768-9562ad05ab50db6c.png)

相信各位看官也差不多看完这张图了，下面我们就来简单了解下其中的类和相关的函数

说到转场动画，其实无非就是我们常用的`push` `pop` `present` `dismiss`四种动画，其中前面两个是成对使用，后面两个成对使用，我们先看看`push`这组在自定义转场动画中所涉及到的类

由于`push`动画组需要配合`navigationController`来使用，所以上图中的`UINavigationControllerDelegate`肯定是我们需要的类

##### UINavigationControllerDelegate

先来看看其中需要用到的函数
```
- (nullable id <UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController
                          interactionControllerForAnimationController:(id <UIViewControllerAnimatedTransitioning>) animationController NS_AVAILABLE_IOS(7_0);

- (nullable id <UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController
                                   animationControllerForOperation:(UINavigationControllerOperation)operation
                                                fromViewController:(UIViewController *)fromVC
                                                  toViewController:(UIViewController *)toVC  NS_AVAILABLE_IOS(7_0);
```

第一个函数的返回值是一个`id <UIViewControllerInteractiveTransitioning>`值
第二个函数返回的值是一个`id <UIViewControllerAnimatedTransitioning>`值
那么我们就先从这两个返回值入手，来看下两个函数的作用

##### UIViewControllerInteractiveTransitioning 、UIPercentDrivenInteractiveTransition

这两个类又是干什么的呢？`UIPercentDrivenInteractiveTransition`遵守协议`UIViewControllerInteractiveTransitioning`,通过查阅资料了解到，`UIPercentDrivenInteractiveTransition`这个类的对象会根据我们的手势，来决定我们的自定义过渡的完成度，也就是这两个其实是和手势交互相关联的，自然而然我们就想到了`iOS 7`引进的侧滑手势，对，就是侧滑手势，说到这里，我就顺带介绍一个类，`UIScreenEdgePanGestureRecognizer`，手势侧滑的类，具体怎么使用，后面我会陆续讲到。

涉及函数
```
//更新进度
- (void)updateInteractiveTransition:(CGFloat)percentComplete;
//取消转场 回到转场前的效果
- (void)cancelInteractiveTransition;
//完成转场 
- (void)finishInteractiveTransition;
```

##### UIViewControllerAnimatedTransitioning

在这个类中，我们又看到了两个函数
```
//转场时间
- (NSTimeInterval)transitionDuration:(nullable id <UIViewControllerContextTransitioning>)transitionContext;

- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext;
```
其中又涉及到一个新的类`UIViewControllerContextTransitioning`，那么这个又是干什么的呢？我们等下再来了解，先来谈谈第一个函数`transitionDuration`，从返回值我们可以猜测出这是和时间有关的，没错，这就是我们自定义转场动画所需要的时间
那么下面我们就来看看`UIViewControllerContextTransitioning`

##### UIViewControllerContextTransitioning

这个类就是我们自定义转场动画所需要的核心，即转场动画的上下文，定义了转场时需要的元素，比如在转场过程中所参与的视图控制器和视图的相关属性
```
//转场动画的容器
@property(nonatomic, readonly) UIView *containerView;
//通过对应的`key`可以得到我们需要的`vc`
- (UIViewController *)viewControllerForKey:(UITransitionContextViewControllerKey)key
//转场动画完成时候调用，必须调用，否则在进行其他转场没有任何效果
- (void)completeTransition:(BOOL)didComplete
```
看到这里，我们现在再去看`UINavigationControllerDelegate `中的两个函数和`UIViewControllerAnimatedTransitioning `中的`animateTransition `函数，就能完全理解了

```
//主要用于手势交互转场 for push or pop
- (nullable id <UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController
                          interactionControllerForAnimationController:(id <UIViewControllerAnimatedTransitioning>) animationController NS_AVAILABLE_IOS(7_0);

//非手势交互转场 for push or pop
- (nullable id <UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController
                                   animationControllerForOperation:(UINavigationControllerOperation)operation
                                                fromViewController:(UIViewController *)fromVC
                                                  toViewController:(UIViewController *)toVC  NS_AVAILABLE_IOS(7_0);

//实现转场动画 通过transitionContext
- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext;

```
到此，我们还有一个类没有了解，那就是`UIViewControllerTransitioningDelegate`有了前面的分析，我们可以很好的理解

##### UIViewControllerTransitioningDelegate

主要是针对`present`和`dismiss`动画的转场
```
//非手势转场交互 for present
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source
//非手势转场交互 for dismiss
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed
//手势交互 for dismiss
- (id<UIViewControllerInteractiveTransitioning>)interactionControllerForDismissal:(id<UIViewControllerAnimatedTransitioning>)animator
//手势交互 for present
- (id<UIViewControllerInteractiveTransitioning>)interactionControllerForPresentation:(id<UIViewControllerAnimatedTransitioning>)animator
```
基本定义和概览我们差不多应该有了一定的了解，正如上图中的简单描述。

了解性的东西说了这么多，下面我们就来点实际性的东西，除了第一张开门那种自定义动画，再来几个比较常用的动画

![CircleSpread.gif](/contentImages/image/jianshu/2525768-b29e25db7cba47cd.gif)

![circleRectSpread.gif](/contentImages/image/jianshu/2525768-cd46b09ac54ba40a.gif)

![page.gif](/contentImages/image/jianshu/2525768-ebef7ba6c2fabc04.gif)

这些动画都比较简单，相信许多大神都很清楚，还望见谅，下面我就对每一种进行分析分析，在分析动画之前，先来看看怎么将上面的各个类进行封装起来，使用更方便，这里不得不感谢很久之前看到的一篇文章，从他的[文章](http://www.cocoachina.com/ios/20160629/16856.html)中收获非常大。

在学习转场动画的时候，虽然对所有类的关系有了一定了解，但是封装的时候，完全没有想到还有这么好的思路，确实是学习了。下面我们就一起来看看封装思路。

#### 封装思路

##### 1. 新建一个综合管理转场动画的类

作用：主要是管理转场所需要的一些设置，诸如转场时间和转场的实现（主要是在子类中进行实现，分离开来），用户在自定义转场动画的时候，只需要继承该类并重写父类方法就可以
类名：`GLTransitionManager`，需要准守的协议有`<UINavigationControllerDelegate,UIViewControllerTransitioningDelegate>`
通过这样，就可以将`present`和`push`动画相关的操作在该类中进行管理
`GLTransitionManager.h`中具体方法
```
@interface GLTransitionManager : NSObject<UINavigationControllerDelegate,UIViewControllerTransitioningDelegate>

/**
 转场动画的时间 默认为0.5s
 */
@property (nonatomic,assign) NSTimeInterval duration;

/**
 入场动画 
 
 @param contextTransition 实现动画
 */
- (void)setToAnimation:(id<UIViewControllerContextTransitioning>)contextTransition;

/**
 退场动画
 
 @param contextTransition 实现动画
 */
- (void)setBackAnimation:(id<UIViewControllerContextTransitioning>)contextTransition;
```
相信大家也看到了在入场和退场动画中都有`(id<UIViewControllerContextTransitioning>) contextTransition `这么一个参数，通过该参数，我们可以获取转场动画的相关`vc`和其他信息，进行转场动画的实现，即我们在自定义转场动画的时候，只需要重写该两个方法就可以，通过`contextTransition`来实现动画，而`<UIViewControllerContextTransitioning>`又在`UIViewControllerAnimatedTransitioning`协议的方法`- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext`中涉及到，于是我又新建了一个准守协议`UIViewControllerAnimatedTransitioning`的类`GLTransitionAnimation`，也就是下面我们将的类

##### 2.转场动画配置及实现类

作用：虽然是配置和实现类，但是在该类中并没有进行实现，这里也正是之前那个博主的高明之处，至少我是这么认为的。在该类中，我们用`block`的传值方法将其传入到我们的管理类中，也就是`GLTransitionManager `

`GLTransitionAnimation.h`文件
```
/**
 GLTransitionAnimation 块

@param contextTransition 将满足UIViewControllerContextTransitioning协议的对象传到管理内 在管理类对动画统一实现
 */
typedef void(^GLTransitionAnimationBlock)(id <UIViewControllerContextTransitioning> contextTransition);

@interface GLTransitionAnimation : NSObject<UIViewControllerAnimatedTransitioning>

@property (nonatomic,copy) GLTransitionAnimationBlock animationBlock;

/**
 初始化方法

@param duration 转场时间
 @return 返回
 */
- (id)initWithDuration:(NSTimeInterval)duration;
```
`GLTransitionAnimation.m`文件比较简单，这里就先不详说，我们先回到管理类中，来看看怎么使用

`GLTransitionManager.m`文件，
在此种定义两个属性
```
/**
 入场动画
 */
@property (nonatomic,strong) GLTransitionAnimation *toTransitionAnimation;

/**
 退场动画
 */
@property (nonatomic,strong) GLTransitionAnimation *backTransitionAnimation;
```
实现方法
```
#pragma mark == 懒加载
- (GLTransitionAnimation *)toTransitionAnimation
{
    if (nil == _toTransitionAnimation) {
        __weak typeof(self) weakSelf = self;
        _toTransitionAnimation = [[GLTransitionAnimation alloc] initWithDuration:self.duration ];
        _toTransitionAnimation.animationBlock = ^(id<UIViewControllerContextTransitioning> contextTransition)
        {
            [weakSelf setToAnimation:contextTransition];
        };
    }
    return _toTransitionAnimation;
}

- (GLTransitionAnimation *)backTransitionAnimation
{
    if (nil == _backTransitionAnimation) {
        __weak typeof(self) weakSelf = self;
        _backTransitionAnimation = [[GLTransitionAnimation alloc] initWithDuration:self.duration];
        _backTransitionAnimation.animationBlock = ^(id<UIViewControllerContextTransitioning> contextTransition)
        {
            [weakSelf setBackAnimation:contextTransition];
        };
    }
    return _backTransitionAnimation;
}

```

通过上面这一方法，我们就很好的将关键参数和对外接口联系起来了。这样我们就只需要在`setToAnimation`和`setBackAnimation`进行转场动画的具体实现即可。
当然这里还有一个小问题，相信各位也发现了，就是为什么将属性定义在了`.m`文件里呢？是的，这里确实是定义在了`.m`文件中，其实就是为了更少的暴露不需要的。

搞定这个之后，我们在来看看，在上面时候，调用该属性呢？
下面我们就来看具体使用的地方
```
//非手势转场交互 for present
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source{
    return self.toTransitionAnimation;
}

//非手势转场交互 for dismiss
- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed{
    return self.backTransitionAnimation;
}

//================
//非手势转场交互 for push or pop
/*****注释:通过 fromVC 和 toVC 我们可以在此设置需要自定义动画的类 *****/
- (id <UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController
                                   animationControllerForOperation:(UINavigationControllerOperation)operation
                                                fromViewController:(UIViewController *)fromVC
                                                  toViewController:(UIViewController *)toVC
{
    _operation = operation;
    
    if (operation == UINavigationControllerOperationPush)
    {
        return self.toTransitionAnimation;
    }
    else if (operation == UINavigationControllerOperationPop)
    {
        return self.backTransitionAnimation;
    }
    else
    {
        return nil;
    }
}
```
在这两个地方使用后，我们差不多就完成了一半了，那还一部分呢？那就是我们的手势滑动，下面我们就来看看手势滑动。

##### 3.手势交互管理类

作用：主要通过侧滑手势来管理交互，在iOS 7后引入新的类`UIPercentDrivenInteractiveTransition`，该类的对象会根据我们的手势，来决定我们的自定义过渡的完成度，所以此次我采用继承的方式，然后在继承的类中加入滑动手势类，这里加入的是侧滑手势类`UIScreenEdgePanGestureRecognizer`，这个类也就是我定义的`GLInteractiveTransition`类

`GLInteractiveTransition.h`文件

```

/**
 手势的方向枚举

- GLPanEdgeTop:屏幕上方
 - GLPanEdgeLeft:屏幕左侧
 - GLPanEdgeBottom: 屏幕下方
 - GLPanEdgeRight: 屏幕右方
 */
typedef NS_ENUM(NSInteger,GLEdgePanGestureDirection) {
    GLPanEdgeTop    = 0,
    GLPanEdgeLeft,
    GLPanEdgeBottom,
    GLPanEdgeRight
};

///**
// 手势转场类型
//
// - GLInteractiveTransitionPush: push
// - GLInteractiveTransitionPop: pop
// - GLInteractiveTransitionPresent: present
// - GLInteractiveTransitionDismiss: dismiss
// */
//typedef NS_ENUM(NSInteger,GLInteractiveTransitionType) {
//    GLInteractiveTransitionPush = 0,
//    GLInteractiveTransitionPop,
//    GLInteractiveTransitionPresent ,
//    GLInteractiveTransitionDismiss
//};

@interface GLInteractiveTransition : UIPercentDrivenInteractiveTransition

/**
 是否满足侧滑手势交互
 */
@property (nonatomic,assign) BOOL isPanGestureInteration;

/**
 转场时的操作 不用传参数的block
 */
@property (nonatomic,copy) dispatch_block_t eventBlcok;

/**
 添加侧滑手势

@param view 添加手势的view
 @param direction 手势的方向
 */
- (void)addEdgePageGestureWithView:(UIView *)view direction:(GLEdgePanGestureDirection)direction;

```

在`.h`文件中，定义了两个属性，一个是用来判断是否需满足侧滑手势，这个在后面会讲到。另一个是用来在侧滑的时候执行所需要的转场的`block`，之前本来是没有加这个的，但是在后面使用的时候，由于想加侧滑的`present`和`push`效果，所以就加了一个。

下面看看`.m`文件滑动手势中的具体实现
```
- (void)handlePopRecognizer:(UIPanGestureRecognizer*)recognizer {
    // 计算用户手指划了多远
    
    CGFloat progress = fabs([recognizer translationInView:self.gestureView].x) / (self.gestureView.bounds.size.width * 1.0);
    progress = MIN(1.0, MAX(0.0, progress));
        
    switch (recognizer.state) {
        case UIGestureRecognizerStateBegan:
        {
            _isPanGestureInteration = YES;
            
            if (self.eventBlcok) {
                self.eventBlcok();
            }
            
            // 创建过渡对象，弹出viewController
//            
//            UIViewController *fromVc = [self gl_viewController];
//            
//            switch (self.transitionType) {
//                case GLInteractiveTransitionPush:
//                {
//                    
//                }
//                    break;
//                case GLInteractiveTransitionPop:
//                {
//                    if (fromVc.navigationController) {
//                        [fromVc.navigationController popViewControllerAnimated:YES];
//                    }
//                }
//                    break;
//                case GLInteractiveTransitionPresent:
//                {
//                    
//                }
//                    break;
//                case GLInteractiveTransitionDismiss:
//                {
//                    [fromVc dismissViewControllerAnimated:YES completion:nil];
//                }
//                    break;
//                default:
//                    break;
//            }
            break;
        }
        case UIGestureRecognizerStateChanged:
        {
            // 更新 interactive transition 的进度
            [self updateInteractiveTransition:progress];
            break;
        }
        case UIGestureRecognizerStateEnded:
        case UIGestureRecognizerStateCancelled:
        {
//            NSLog(@" 打印信息:%f",progress);
            // 完成或者取消过渡
            if (progress > 0.5) {
                [self finishInteractiveTransition];
            }
            else {
                [self cancelInteractiveTransition];
            }
            
            _isPanGestureInteration = NO;
            break;
        }
        default:
            break;
    }
}
```
手势交互管理类的核心代码差不多就这么多，下面我们看看怎么使用

##### 4.`UIViewController + GLTransition`

为了和系统的转场动画的函数区分开来，这里我新建了一个`UIViewController`的`category`类`UIViewController + GLTransition`，在其中定义了四个函数，分别如下
```
/**
 push动画

@param viewController 被push viewController
 @param transitionManager 控制类
 */
- (void)gl_pushViewControler:(UIViewController *)viewController withAnimation:(GLTransitionManager*)transitionManager;

/**
 present动画

@param viewController 被present viewController
 @param transitionManager 控制类
 */
- (void)gl_presentViewControler:(UIViewController *)viewController withAnimation:(GLTransitionManager*)transitionManager;

/**
 注册入场手势

@param direction 方向
 @param blcok 手势转场触发的点击事件
 */
- (void)gl_registerToInteractiveTransitionWithDirection:(GLEdgePanGestureDirection)direction eventBlcok:(dispatch_block_t)blcok;

/**
 注册返回手势

@param direction 侧滑方向
 @param blcok 手势转场触发的点击事件
 */
- (void)gl_registerBackInteractiveTransitionWithDirection:(GLEdgePanGestureDirection)direction eventBlcok:(dispatch_block_t)blcok;

```
下面我们看看具体实现
`UIViewController (GLTransition).m`文件
```
- (void)gl_pushViewControler:(UIViewController *)viewController withAnimation:(GLTransitionManager *)transitionManager
{
    if (!viewController) {
        return;
    }
    if (!transitionManager) {
        return;
    }
    
    if (self.navigationController) {
        
        self.navigationController.delegate = transitionManager;
        
        GLInteractiveTransition *toInteractiveTransition = objc_getAssociatedObject(self, &kToAnimationKey);
        if (toInteractiveTransition) {
            [transitionManager setValue:toInteractiveTransition forKey:@"toInteractiveTransition"];
        }
        
        objc_setAssociatedObject(viewController, &kAnimationKey, transitionManager, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
        [self.navigationController pushViewController:viewController animated:YES];
   
    }
}

- (void)gl_presentViewControler:(UIViewController *)viewController withAnimation:(GLTransitionManager *)transitionManager
{
    if (!viewController) {
        return;
    }
    if (!transitionManager) {
        return;
    }
    //present 动画代理 被执行动画的vc设置代理
    viewController.transitioningDelegate = transitionManager;
    
    GLInteractiveTransition *toInteractiveTransition = objc_getAssociatedObject(self, &kToAnimationKey);
    if (toInteractiveTransition) {
        [transitionManager setValue:toInteractiveTransition forKey:@"toInteractiveTransition"];
    }
    objc_setAssociatedObject(viewController, &kAnimationKey, transitionManager, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    
    [self presentViewController:viewController animated:YES completion:nil];
}

- (void)gl_registerToInteractiveTransitionWithDirection:(GLEdgePanGestureDirection)direction eventBlcok:(dispatch_block_t)blcok
{
    GLInteractiveTransition *interactiveTransition = [[GLInteractiveTransition alloc] init];
    interactiveTransition.eventBlcok = blcok;
    [interactiveTransition addEdgePageGestureWithView:self.view direction:direction];
    
    objc_setAssociatedObject(self, &kToAnimationKey, interactiveTransition, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (void)gl_registerBackInteractiveTransitionWithDirection:(GLEdgePanGestureDirection)direction eventBlcok:(dispatch_block_t)blcok
{
    GLInteractiveTransition *interactiveTransition = [[GLInteractiveTransition alloc] init];
    interactiveTransition.eventBlcok = blcok;
    [interactiveTransition addEdgePageGestureWithView:self.view direction:direction];
    
    //判读是否需要返回 然后添加侧滑
    GLTransitionManager *animator = objc_getAssociatedObject(self, &kAnimationKey);
    if (animator)
    {
        //用kvc的模式  给 animator的backInteractiveTransition 退场赋值
        [animator setValue:interactiveTransition forKey:@"backInteractiveTransition"];
    }
}
```

在`push`和`present`中，有几个需要注意的地方
1、`self.navigationController.delegate = transitionManager`
2、`viewController.transitioningDelegate = transitionManager`
上面两个主要是将`navigationController`的代理和`viewController`的`transitioningDelegate`指向对象`transitionManager`，这个对象是准守了`<UINavigationControllerDelegate,UIViewControllerTransitioningDelegate>`两个协议的，这样我们就能够在`push`和`present`的时候，简单的去调协议方法。

3、设置手势交互转场
```
        GLInteractiveTransition *toInteractiveTransition = objc_getAssociatedObject(self, &kToAnimationKey);
        if (toInteractiveTransition) {
            [transitionManager setValue:toInteractiveTransition forKey:@"toInteractiveTransition"];
        }
```
在`push`和`present`方法中，都有这样的代码，这里为了减少不必要的暴露，在`GLTransitionManager.m`文件中，我还定义了两个属性
```
/**
 入场手势
 */
@property (nonatomic,strong) GLInteractiveTransition *toInteractiveTransition;

/**
 退场手势
 */
@property (nonatomic,strong) GLInteractiveTransition *backInteractiveTransition;
```
并且通过`kvc`的方式对其进行赋值，当转场动画进行的时候，会先去调用非转场动画的方法，比如`push`的时候，会先调用
```
- (id <UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController
                                   animationControllerForOperation:(UINavigationControllerOperation)operation
                                                fromViewController:(UIViewController *)fromVC
                                                  toViewController:(UIViewController *)toVC
```
然后再调用手势交互
```
//手势交互 for push or pop
- (id<UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController interactionControllerForAnimationController:(id<UIViewControllerAnimatedTransitioning>)animationController
```
这个时候，我们就需要加一个判断，也就是通过`GLInteractiveTransition`类中的是否满足侧滑手势交互`isPanGestureInteration`这个属性来判断，前面在侧滑手势刚刚进行的时候，就对其进行了赋值，并设置为`yes`，对应的实现代码就是
```
- (id<UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController interactionControllerForAnimationController:(id<UIViewControllerAnimatedTransitioning>)animationController
{
    if (_operation == UINavigationControllerOperationPush) {
        return self.toInteractiveTransition.isPanGestureInteration ? self.toInteractiveTransition:nil;
    }
    else{
        return self.backInteractiveTransition.isPanGestureInteration ? self.backInteractiveTransition:nil;
    }
}
```
如果返回的为`nil`，那么就不会去调用手势交互类，否则则会调用。同理，`present`的时候也是一样
所以就有了下面的代码
```
//手势交互 for dismiss
- (id<UIViewControllerInteractiveTransitioning>)interactionControllerForDismissal:(id<UIViewControllerAnimatedTransitioning>)animator{
    return self.backInteractiveTransition.isPanGestureInteration ? self.backInteractiveTransition:nil;
}

//手势交互 for present
- (id<UIViewControllerInteractiveTransitioning>)interactionControllerForPresentation:(id<UIViewControllerAnimatedTransitioning>)animator{
   return self.toInteractiveTransition.isPanGestureInteration ? self.toInteractiveTransition:nil;
}
```
在`UIViewController + GLTransition`中的`push`和`present`函数中，还有一个需要注意的地方，那就是
```
objc_setAssociatedObject(viewController, &kAnimationKey, transitionManager, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
```
这里通过`runtime`的方式给`vc`设置了一个属性值，为什么这么做呢？因为在`arc`下，如果我们在使用`GLTransitionManager`的时候去创建一个对象而非`vc`的属性，那么在`push`的时候`GLTransitionManager`这个对象就会被系统释放掉，这样我们后面所有有关转场的操作就不能再实现了，或许我们可以给`vc`建一个`base`类，然后添加一个`GLTransitionManager`对象的属性，但是这样或许有点复杂，所有这里就这样处理了。

在`UIViewController + GLTransition`中还有两个函数的实现，其原理，我相信大家应该都能看明白了，就不再详细说明了
```
- (void)gl_registerToInteractiveTransitionWithDirection:(GLEdgePanGestureDirection)direction eventBlcok:(dispatch_block_t)blcok
{
    GLInteractiveTransition *interactiveTransition = [[GLInteractiveTransition alloc] init];
    interactiveTransition.eventBlcok = blcok;
    [interactiveTransition addEdgePageGestureWithView:self.view direction:direction];
    
    objc_setAssociatedObject(self, &kToAnimationKey, interactiveTransition, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

文章有点长，希望大家能够理解，因为后面还有。。。。

#### 几个动画的具体实现

##### 1、开门动画

由于我们已经有了基类``，所以当我们需要实现什么动画的时候，只需要集成该类就可以了

针对开门动画我新建了下面这么一个类`GLTransitionManager`
```
@interface GLOpenDoorAnimation : GLTransitionManager

@end
```
然后在重新父类的方法
```
- (void)setToAnimation:(id<UIViewControllerContextTransitioning>)contextTransition
```
具体实现
1、根据`id<UIViewControllerContextTransitioning>`对象先得到几个关键值，目标`vc`和当前`vc`和容器`containerView`
```
    //获取目标动画的VC
    UIViewController *toVc = [contextTransition viewControllerForKey:UITransitionContextToViewControllerKey];
    UIViewController *fromVc = [contextTransition viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIView *containerView = [contextTransition containerView];
```

2、由于是开门动画，所以其过程大概是这样的：当前`vc`逐渐缩小，目标`vc`慢慢从屏幕两边移到中间，但是我们又不能把目标`vc`的`view`分成两个部分，所以这里我们可以利用截图，来给用户造成一个假象。先截两个图，然后分别让其坐标居于屏幕外，然后用动画让其慢慢移动到屏幕中间，动画完成的时候，移除当前两个截图。这里有个小问题，那就是当前`vc`的缩放，虽然我们能够使其缩小，但是这样，如果涉及到侧滑手势的话，问题就来了。因为`view`的宽发生了变化，这样我们根据宽度来计算滑动的距离，从而更新转场动画的时候就会出现问题，导致
```
- (void)handlePopRecognizer:(UIPanGestureRecognizer*)recognizer {
    // 计算用户手指划了多远
    
    CGFloat progress = fabs([recognizer translationInView:self.gestureView].x) / (self.gestureView.bounds.size.width * 1.0);
    progress = MIN(1.0, MAX(0.0, progress));
```

中的`progress `出现问题。所以这里也就采用了截图的方式，对该截图进行缩放，而不去修改`vc`的`view`。

下面看下核心代码
```
- (void)setToAnimation:(id<UIViewControllerContextTransitioning>)contextTransition
{
    //获取目标动画的VC
    UIViewController *toVc = [contextTransition viewControllerForKey:UITransitionContextToViewControllerKey];
    UIViewController *fromVc = [contextTransition viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIView *containerView = [contextTransition containerView];
    
    UIView *fromView = fromVc.view;
    UIView *toView = toVc.view;
    
    //截图
    UIView *toView_snapView = [toView snapshotViewAfterScreenUpdates:YES];
    
    CGRect left_frame = CGRectMake(0, 0, CGRectGetWidth(fromView.frame) / 2.0, CGRectGetHeight(fromView.frame));
    CGRect right_frame = CGRectMake(CGRectGetWidth(fromView.frame) / 2.0, 0, CGRectGetWidth(fromView.frame) / 2.0, CGRectGetHeight(fromView.frame));
    UIView *from_left_snapView = [fromView resizableSnapshotViewFromRect:left_frame
                                                         afterScreenUpdates:NO
                                                              withCapInsets:UIEdgeInsetsZero];
    
    UIView *from_right_snapView = [fromView resizableSnapshotViewFromRect:right_frame
                                                         afterScreenUpdates:NO
                                                              withCapInsets:UIEdgeInsetsZero];
    
    toView_snapView.layer.transform = CATransform3DMakeScale(0.7, 0.7, 1);
    from_left_snapView.frame = left_frame;
    from_right_snapView.frame = right_frame;
    
    //将截图添加到 containerView 上
    [containerView addSubview:toView_snapView];
    [containerView addSubview:from_left_snapView];
    [containerView addSubview:from_right_snapView];
    
    fromView.hidden = YES;
    
    [UIView animateWithDuration:self.duration delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
        //左移
        from_left_snapView.frame = CGRectOffset(from_left_snapView.frame, -from_left_snapView.frame.size.width, 0);
        //右移
        from_right_snapView.frame = CGRectOffset(from_right_snapView.frame, from_right_snapView.frame.size.width, 0);
        
        toView_snapView.layer.transform = CATransform3DIdentity;
        
    } completion:^(BOOL finished) {
        fromView.hidden = NO;
        
        [from_left_snapView removeFromSuperview];
        [from_right_snapView removeFromSuperview];
        [toView_snapView removeFromSuperview];
        
        if ([contextTransition transitionWasCancelled]) {
            [containerView addSubview:fromView];
        } else {
            [containerView addSubview:toView];
        }
        [contextTransition completeTransition:![contextTransition transitionWasCancelled]];
    }];
}
```
`setBackAnimation`动画和上面的大同小异，就不再详细说明，文章后面有`demo`地址，大家可以看看。

##### 2、圆圈逐渐放大转场动画

在做动画之前，我们先要了解其大概原理
这里我简单的做了个草图

![Paste_Image.png](/contentImages/image/jianshu/2525768-b0638aceb3247fa1.png)
小圆和大圆分别表示动画前和动画后
这里我们采用的是`UIBezierPath + mask + CAShapeLayer`的策略对其进行实习

大家都知道，`UIBezierPath`可以画圆形，而`CAShapeLayer`又具备`CGPathRef path`属性，可以和`UIBezierPath`联系起来，而`UIView`又具备`CALayer *mask`属性，这样三者就这么巧妙的联系起来了。
在这里，我们使用`CABasicAnimation`动画，通过对其设置`[CABasicAnimation animationWithKeyPath:@"path"]`来让其执行我们想要的`path`路径动画
于是就有了下面的代码
```
- (void)setToAnimation:(id<UIViewControllerContextTransitioning>)contextTransition
{
    //获取目标动画的VC
    UIViewController *toVc = [contextTransition viewControllerForKey:UITransitionContextToViewControllerKey];
    UIView *containerView = [contextTransition containerView];
    [containerView addSubview:toVc.view];
    
    //创建UIBezierPath路径 作为后面动画的起始路径
    UIBezierPath *startPath = [UIBezierPath bezierPathWithArcCenter:self.centerPoint radius:self.radius startAngle:0 endAngle:2*M_PI clockwise:YES];
    
    //创建结束UIBezierPath
    //首先我们需要得到后面路径的半径  半径应该是距四个角最远的距离
    CGFloat x = self.centerPoint.x;
    CGFloat y = self.centerPoint.y;
    //取出其中距屏幕最远的距离 来求围城矩形的对角线 即我们所需要的半径
    CGFloat radius_x = MAX(x, containerView.frame.size.width - x);
    CGFloat radius_y = MAX(y, containerView.frame.size.height - y);
    //补充下 sqrtf求平方根   double pow(double x, double y); 求 x 的 y 次幂（次方）
    //通过勾股定理算出半径
    CGFloat endRadius = sqrtf(pow(radius_x, 2) + pow(radius_y, 2));
    
    UIBezierPath *endPath = [UIBezierPath bezierPathWithArcCenter:self.centerPoint radius:endRadius startAngle:0 endAngle:2*M_PI clockwise:YES];
    
//    self.endPath = endPath;
    
    //创建CAShapeLayer 用以后面的动画
    CAShapeLayer *shapeLayer = [CAShapeLayer layer];
    shapeLayer.path = endPath.CGPath;
    toVc.view.layer.mask = shapeLayer;
    
    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"path"];
    animation.fromValue = (__bridge id _Nullable)(startPath.CGPath);
    animation.duration = self.duration;
    animation.delegate = (id)self;
//    animation.removedOnCompletion = NO;//执行后移除动画
    //保存contextTransition  后面动画结束的时候调用
    [animation setValue:contextTransition forKey:@"pathContextTransition"];
    [shapeLayer addAnimation:animation forKey:nil];
    
    self.maskShapeLayer = shapeLayer;
}
```
由于代码中有比较详细的说明，所以这里就不再详细说明，`setBackAnimation`也大同小异

##### 3、圆圈和目标vc共同缩放转场动画

这个比较简单，主要是利用`UIView`的缩放进行的，由于目标`vc`的上角和圆是相切的，所以，这里我们可以先假设目标`vc`处于正常状态，然后再跟进小圆的中心，画一个大圆，让其和目标`vc`一起缩放就是。这里留了一个缺陷，那就是不支持侧滑，因为我是用目标`vc`进行缩放的，而没有截图，大家可以试试。
其实现大概为

```
- (CGRect)frameToCircle:(CGPoint)centerPoint size:(CGSize)size
{
    CGFloat radius_x = fmax(centerPoint.x, size.width - centerPoint.x);
    CGFloat radius_y = fmax(centerPoint.y, size.height - centerPoint.y);
    CGFloat endRadius = 2 * sqrtf(pow(radius_x, 2) + pow(radius_y, 2));

CGRect rect = {CGPointZero,CGSizeMake(endRadius, endRadius)};
    
    return rect;
}

##### 4、翻书效果

这个还是花了些时间，主要不在思想上，而是在翻书有个阴影效果哪里，等下我会讲到。先说说思路，主要还是通过截图来实现。首先需要截当前`vc`的部分，如果向左滑则截右边，向右则截左，然后还需要截目标`vc`的两部分图，分别加到`containerView`上，假如现在向左翻，那么就要将目标`vc`的左边截图加到`containerView`的左边并且隐藏起来，让其绕`y`轴旋转`M_PI_2`，就是直插屏幕的样子，那么目标`vc`的右边截图就需要放到当前`vc`的下面，这样当当前`vc`在滑动的时候，我们就能看到下面的图了。当当前`vc`绕`y`轴旋转`-M_PI_2`的时候，目标`vc`的左边截图显示出来，并恢复原状，完成整副动画。
需要注意的是，截图在绕`y`轴旋转的时候，因为我们的`layer`的默认`anchorPoint`为`(0.5,0.5)`，所以需要改变`anchorPoint`的只，否则就绕中心在旋转了。

说了这么多，还是看看核心代码吧
```
p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Menlo; color: #3d71ff}p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Menlo; color: #4dbf56}p.p3 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Menlo; color: #00afca}p.p4 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Menlo; color: #3d71ff; min-height: 16.0px}p.p5 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px Menlo; color: #2337da}p.p6 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px 'PingFang SC'; color: #4dbf56}span.s1 {font-variant-ligatures: no-common-ligatures}span.s2 {font-variant-ligatures: no-common-ligatures; color: #c2349b}span.s3 {font-variant-ligatures: no-common-ligatures; color: #00afca}span.s4 {font-variant-ligatures: no-common-ligatures; color: #3d71ff}span.s5 {font: 14.0px 'PingFang SC'; font-variant-ligatures: no-common-ligatures}span.s6 {font-variant-ligatures: no-common-ligatures; color: #4dbf56}span.s7 {font: 14.0px 'PingFang SC'; font-variant-ligatures: no-common-ligatures; color: #4dbf56}span.s8 {font: 14.0px Menlo; font-variant-ligatures: no-common-ligatures; color: #2337da}span.s9 {font: 14.0px Menlo; font-variant-ligatures: no-common-ligatures; color: #3d71ff}span.s10 {font: 14.0px Menlo; font-variant-ligatures: no-common-ligatures}span.s11 {font-variant-ligatures: no-common-ligatures; color: #8b84cf}span.s12 {font-variant-ligatures: no-common-ligatures; color: #93c96a}span.s13 {font-variant-ligatures: no-common-ligatures; color: #d28f5a}

- (void)setToAnimation:(id<UIViewControllerContextTransitioning>)contextTransition
{
    //获取目标动画的VC
    UIViewController *toVc = [contextTransition viewControllerForKey:UITransitionContextToViewControllerKey];
    UIViewController *fromVc = [contextTransition viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIView *containerView = [contextTransition containerView];
    
    //m34 这个参数有点不好理解  为透视效果 我在http://www.jianshu.com/p/e8d1985dccec这里有讲
    //当Z轴上有变化的时候 我们所看到的透视效果 可以对比看看 当你改成-0.1的时候 就懂了
    CATransform3D transform = CATransform3DIdentity;
    transform.m34 = -0.002;
    [containerView.layer setSublayerTransform:transform];
    
    UIView *fromView = fromVc.view;
    UIView *toView = toVc.view;
    
    //截图
    //当前页面的右侧
    CGRect from_half_right_rect = CGRectMake(fromView.frame.size.width/2.0, 0, fromView.frame.size.width/2.0, fromView.frame.size.height);
    //目标页面的左侧
    CGRect to_half_left_rect = CGRectMake(0, 0, toView.frame.size.width/2.0, toView.frame.size.height);
    //目标页面的右侧
    CGRect to_half_right_rect = CGRectMake(toView.frame.size.width/2.0, 0, toView.frame.size.width/2.0, toView.frame.size.height);
    
    //截三张图 当前页面的右侧 目标页面的左和右
    UIView *fromRightSnapView = [fromView resizableSnapshotViewFromRect:from_half_right_rect afterScreenUpdates:NO withCapInsets:UIEdgeInsetsZero];
    UIView *toLeftSnapView = [toView resizableSnapshotViewFromRect:to_half_left_rect afterScreenUpdates:YES withCapInsets:UIEdgeInsetsZero];
    UIView *toRightSnapView = [toView resizableSnapshotViewFromRect:to_half_right_rect afterScreenUpdates:YES withCapInsets:UIEdgeInsetsZero];
    
    
    fromRightSnapView.frame = from_half_right_rect;
    toLeftSnapView.frame = to_half_left_rect;
    toRightSnapView.frame = to_half_right_rect;
    
    //重新设置anchorPoint  分别绕自己的最左和最右旋转
    fromRightSnapView.layer.position = CGPointMake(CGRectGetMinX(fromRightSnapView.frame), CGRectGetMinY(fromRightSnapView.frame) + CGRectGetHeight(fromRightSnapView.frame) * 0.5);
    fromRightSnapView.layer.anchorPoint = CGPointMake(0, 0.5);
    
    toLeftSnapView.layer.position = CGPointMake(CGRectGetMinX(toLeftSnapView.frame) + CGRectGetWidth(toLeftSnapView.frame), CGRectGetMinY(toLeftSnapView.frame) + CGRectGetHeight(toLeftSnapView.frame) * 0.5);
    toLeftSnapView.layer.anchorPoint = CGPointMake(1, 0.5);
    
    //添加阴影效果

UIView *fromRightShadowView = [self addShadowView:fromRightSnapView startPoint:CGPointMake(0, 1) endPoint:CGPointMake(1, 1)];
    UIView *toLeftShaDowView = [self addShadowView:toLeftSnapView startPoint:CGPointMake(1, 1) endPoint:CGPointMake(0, 1)];
    
    //添加视图  注意顺序
    [containerView insertSubview:toView atIndex:0];
    [containerView addSubview:toLeftSnapView];
    [containerView addSubview:toRightSnapView];
    [containerView addSubview:fromRightSnapView];

toLeftSnapView.hidden = YES;
    
    
    //先旋转到最中间的位置
    toLeftSnapView.layer.transform = CATransform3DMakeRotation(M_PI_2, 0, 1, 0);
    //StartTime 和 relativeDuration 均为百分百
    [UIView animateKeyframesWithDuration:self.duration delay:0 options:UIViewKeyframeAnimationOptionCalculationModeLinear animations:^{
        [UIView addKeyframeWithRelativeStartTime:0 relativeDuration:0.5 animations:^{
            
            fromRightSnapView.layer.transform = CATransform3DMakeRotation(-M_PI_2, 0, 1, 0);
            fromRightShadowView.alpha = 1.0;
        }];
        
        [UIView addKeyframeWithRelativeStartTime:0.5 relativeDuration:0.5 animations:^{
            toLeftSnapView.hidden = NO;
            toLeftSnapView.layer.transform = CATransform3DIdentity;
            toLeftShaDowView.alpha = 0.0;
        }];
    } completion:^(BOOL finished) {
        [toLeftSnapView removeFromSuperview];
        [toRightSnapView removeFromSuperview];
        [fromRightSnapView removeFromSuperview];
        [fromView removeFromSuperview];
        
        if ([contextTransition transitionWasCancelled]) {
            [containerView addSubview:fromView];
        }
        
        [contextTransition completeTransition:![contextTransition transitionWasCancelled]];
    }];
    
    
    
//本来打算用基础动画来实现 但是由于需要保存几个变量 在动画完成的代理函数中用，所以就取消这个想法了
//    CABasicAnimation *fromRightAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.x"];
//    fromRightAnimation.duration = self.duration/2.0;
//    fromRightAnimation.beginTime = CACurrentMediaTime();
//    fromRightAnimation.toValue = @(-M_PI_2);
//    [fromRightSnapView.layer addAnimation:fromRightAnimation forKey:nil];
//    
//    
//    CABasicAnimation *toLeftAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.x"];
//    toLeftAnimation.beginTime = CACurrentMediaTime() + self.duration/2.0;
//    toLeftAnimation.fromValue = @(M_PI_2);
//    [toLeftAnimation setValue:contextTransition forKey:@"contextTransition"];
//    [toLeftSnapView.layer addAnimation:toLeftAnimation forKey:@"toLeftAnimation"];
}
```
#####项目文件截图：
![](/contentImages/image/20170907/LAbSXo6SPeaZkA9P382.jpg)
写到这里，差不多转场动画我能够写的就到这里了，文章实在是有点长，不是故意为之，只是我想写的稍微详细点，对自己也是一个很好的提升。如果能帮到你，还请给个`打赏`，嘿嘿~
如果有什么不对的地方，还请多多指教，共同成长。

iOS 自定义转场动画浅谈

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