iOS的自定义转场动画

好久没更新了，最近一直比较忙，也是有点懒了没更新，实在不好意思，学习的步伐不能停下啊。
　　好了，废话不多说今天来聊一聊iOS的自定义转场的实现。

简述

iOS的新页面的弹出方式分为两种Push&Pop和Present&Dismiss，转场方式的自定义也主要针对这两种方式进行。其中Push&Pop方式需要针对Push和Pop分别定义动画，也就是说需要分别创建动画文件。而Present&Dismiss方式的话只需要一个即可。

Push&Pop方式

动画文件

首先来看一下动画文件的实现，
1、先创建一个类继承自NSObject
2、遵守协议UIViewControllerAnimatedTransitioning
3、接下来主要实现三个方法即可

@interface PushTransition : NSObject
@property (nonatomic,strong) id transitionContext;//专场上下文，用来协调，from和to的页面
@property (nonatomic,strong) UIViewController *fromViewController;//push操作主要针对fromViewController做动画
@end

First

主要用来返回动画执行时间,即为push动画的时间，直接return一个时间即可，单位为秒

- (NSTimeInterval)transitionDuration:(nullable id )transitionContext
{
    return 2;
}

Second

下面这个方法就主要涉及到动画的实现了，需要对FromViewController的view做动画，来实现push的动画效果，主要解释已在注释里面写的很清楚了

- (void)animateTransition:(id )transitionContext
{_transitionContext = transitionContext;//首先记录transitionContext，下面的方法会用到
    //我们主要通过这个transitionContext来获取需要做动画的fromViewController和toViewController,fromView和toView
    //通过viewControllerForKey:这个方法来获取，有两个key来获取相应的Controller
    // Currently only two keys are defined by the system:
    //   UITransitionContextToViewControllerKey  获取要出现的Controller
    //   UITransitionContextFromViewControllerKey 获取要消失的Controller
    // Currently only two keys are defined by the system:
    //   UITransitionContextToViewKey //获取要出现的view即上面toViewController的View
    //   UITransitionContextFromViewKey //获取要出现的view即fromViewController的View
    UIView *fromView = [transitionContext viewForKey:UITransitionContextFromViewKey];
    UIView *toView = [transitionContext viewForKey:UITransitionContextToViewKey];
    //拿到ContainerView
    UIView *containerView = [transitionContext containerView];
    //把fromView和toView都加到containerView中，在容器中是完成动画
    [containerView addSubview:toView];
    [containerView addSubview:fromView];

    //CATransform3D类型的四维仿射变换矩阵，并且提供预置好的进行旋转、变形之后的仿射变换矩阵，m34来控制透视效果,有兴趣的话可以在自己了解一下
    CATransform3D transform = CATransform3DIdentity;
    transform.m34 = -1/500.0;
    fromView.layer.transform = transform;
    fromView.layer.anchorPoint = CGPointMake(0, 0.5);
    fromView.layer.position = CGPointMake(0, CGRectGetMidY(fromView.frame));
    
    //动画变化
    [UIView animateWithDuration:2 animations:^{

        fromView.layer.transform = CATransform3DMakeRotation(-M_PI_2, 0, 1, 0);
        
    } completion:^(BOOL finished) {
// This must be called whenever a transition completes (or is cancelled.)
// Typically this is called by the object conforming to the
// UIViewControllerAnimatedTransitioning protocol that was vended by the transitioning
// delegate.  For purely interactive transitions it should be called by the
// interaction controller. This method effectively updates internal view
// controller state at the end of the transition.
//动画完成后必须调用
        [_transitionContext finishInteractiveTransition];
        [_transitionContext completeTransition:YES];
    }];
}

Pop的话，其实跟Push差不多这里就只贴代码不做过多解释了

- (NSTimeInterval)transitionDuration:(id)transitionContext{
    return 2;
}

- (void)animateTransition:(id)transitionContext{
    
    _transitionContext = transitionContext;
    UIViewController *fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIViewController *toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    [fromViewController.view.layer removeAllAnimations];    
    UIView *containerView = [transitionContext containerView];
    
    [containerView addSubview:fromViewController.view];
    [containerView addSubview:toViewController.view];
    
    CATransform3D transform = CATransform3DIdentity;
    transform.m34 = -1/500.0;
    toViewController.view.layer.transform = transform;
    toViewController.view.layer.anchorPoint = CGPointMake(0, 0.5);
    toViewController.view.layer.position = CGPointMake(0, CGRectGetMidY(fromViewController.view.frame));
    toViewController.view.layer.transform = CATransform3DMakeRotation(-M_PI_2, 0, 1, 0);
    
    [UIView animateWithDuration:2 animations:^{
        
        toViewController.view.layer.transform = CATransform3DIdentity;
        
    } completion:^(BOOL finished) {
        [_transitionContext finishInteractiveTransition];
        [_transitionContext completeTransition:YES];
    }];
    
}

下面我们来介绍一下present和dismiss

这里先简单提一下代理，OC中的代理，实在是十分好用，为了将我们的代码耦合性降低。我们可以单独生成一个类，来实现动画，这样的话可以精简Controller里面的代码，另外是代码的复用性进一步增加。动画文件可以单独放在任何地方应用。
　　下面我们来实现.h

//首先遵循以下两个协议，要实现自定义转场必须遵守的
@interface ModalTransition : NSObject 
@property (nonatomic, assign) BOOL isPresent;//记录是Present还是Dimiss
@end

.m实现，这里我只是很简单的写了一个弹簧动画，对于动画方式大家可以自由发挥，写出更加炫酷的效果

@implementation ModalTransition 

//下面两个代理方法要返回一个遵循UIViewControllerAnimatedTransitioning协议的对象，返回self即可。记录一下是Present还是Dimiss。主要讲解我还放在注释里面
- (id)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source{
    _isPresent = YES;
    return self;
}
- (id)animationControllerForDismissedController:(UIViewController *)dismissed{
    _isPresent = NO;
    return self;
}
//返回动画时间
- (NSTimeInterval)transitionDuration:(id)transitionContext{
    return 1.0;
}
//根据_isPresent来执行不同的动画
- (void)animateTransition:(id)transitionContext{
    _isPresent ? [self animationForPresentedView:transitionContext] : [self animationForDismissView:transitionContext];
}
//自定义方法，Present的动画实现
-(void)animationForPresentedView:(id)transitionContext{
    UIView *presentedView = [transitionContext viewForKey:UITransitionContextToViewKey];
    UIView *fromView = [transitionContext viewForKey:UITransitionContextFromViewKey];
//注意添加的次序
    [[transitionContext containerView] addSubview:fromView];
    [[transitionContext containerView] addSubview:presentedView];
    presentedView.transform = CGAffineTransformTranslate(presentedView.transform, 0, 667);
    [UIView animateWithDuration:[self transitionDuration:transitionContext] delay:0 usingSpringWithDamping:0.6 initialSpringVelocity:0 options:UIViewAnimationOptionCurveEaseInOut animations:^{
        presentedView.transform = CGAffineTransformIdentity;
    } completion:^(BOOL finished) {
//完成后记得调用completeTransition:方法
        [transitionContext completeTransition:YES];
    }];
}
//自定义方法，Present的动画实现
-(void)animationForDismissView:(id)transitionContext{
    UIView *dismissedView = [transitionContext viewForKey:UITransitionContextFromViewKey];
    UIView *toView = [transitionContext viewForKey:UITransitionContextToViewKey];
    [[transitionContext containerView] addSubview:toView];
//注意添加的次序
    [[transitionContext containerView] addSubview:dismissedView];
    [UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
        dismissedView.transform = CGAffineTransformTranslate(dismissedView.transform, 0, 667);
    } completion:^(BOOL finished) {
//完成后记得调用completeTransition:方法
        [transitionContext completeTransition:YES];
    }];
}
@end

使用方法也标简单

   PresentViewController *presentController = [[PresentViewController alloc]init];
    presentController.modalTransitionStyle = UIModalPresentationCustom;
    presentController.transitioningDelegate = _Transition;//_Transition即为上面冬瓜文件生成的对象，这样就可以使用自定义的present动画
    [self presentViewController:presentController animated:YES completion:nil];

到这里基本就实现完成了，不管是Pop&Push还是Present&Dismiss你都可以实现任何你想要的炫酷效果（当然前提是你能把炫酷的动画优雅的实现出来），我这里只是抛砖引玉，期待你有更完美，漂亮的动画效果。