iOS自定义转场动画（3）——自定义模态跳转之Present

Modal

modal转场方式即使用 presentViewController() 方法推出的方式，默认情况下，第二个视图从屏幕下方弹出。下面就来介绍下 modal 方式转场动画的自定义。

present

还是先来看一下完成的效果

准备

1、创建一个新的工程，删掉Main，在AppDelegate中创建自定义UIWindow，设置rootVC为ViewController。

2、在ViewController中创建一个全屏的ImageView，并且指定一张图片；新建一个按钮用于present。

3、新建一个SecondViewController。同样创建一个全屏的ImageView，指定一张和ViewController不同的图片，新建一个同于dismiss的按钮

开始

1、创建一个文件继承自 NSObject，取名为PresentTransition并在.h中遵守 UIViewControllerAnimatedTransitioning协议。

2、实现协议的两个方法，并在其中编写 Push 的动画。 具体的动画实现过程都在代码的注释里：

// 返回动画的时间- (NSTimeInterval)transitionDuration:(nullable id <UIViewControllerContextTransitioning>)transitionContext{    return 0.8;}- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext{    ViewController * fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];    SecondViewController * toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];    UIView * container = [transitionContext containerView];    [container addSubview:toVC.view];    [container bringSubviewToFront:fromVC.view];    // 改变m34    CATransform3D transfrom = CATransform3DIdentity;    transfrom.m34 = -0.002;    container.layer.sublayerTransform = transfrom;    // 设置archPoint和position    CGRect initalFrame = [transitionContext initialFrameForViewController:fromVC];    toVC.view.frame = initalFrame;    fromVC.view.frame = initalFrame;    fromVC.view.layer.anchorPoint = CGPointMake(0, 0.5);    fromVC.view.layer.position = CGPointMake(0, initalFrame.size.height / 2.0);    // 添加阴影效果    CAGradientLayer * shadowLayer = [[CAGradientLayer alloc] init];    shadowLayer.colors =@[                         [UIColor colorWithWhite:0 alpha:1],                         [UIColor colorWithWhite:0 alpha:0.5],                         [UIColor colorWithWhite:1 alpha:0.5]                         ];    shadowLayer.startPoint = CGPointMake(0, 0.5);    shadowLayer.endPoint = CGPointMake(1, 0.5);    shadowLayer.frame = initalFrame;    UIView * shadow = [[UIView alloc] initWithFrame:initalFrame];    shadow.backgroundColor = [UIColor clearColor];    [shadow.layer addSublayer:shadowLayer];    [fromVC.view addSubview:shadow];    shadow.alpha = 0;    // 动画    [UIView animateKeyframesWithDuration:[self transitionDuration:transitionContext] delay:0 options:2 animations:^{        fromVC.view.layer.transform = CATransform3DMakeRotation(-M_PI_2, 0, 1, 0);        shadow.alpha = 1.0;    } completion:^(BOOL finished) {        fromVC.view.layer.anchorPoint = CGPointMake(0.5, 0.5);        fromVC.view.layer.position = CGPointMake(CGRectGetMidX(initalFrame), CGRectGetMidY(initalFrame));        fromVC.view.layer.transform = CATransform3DIdentity;        [shadow removeFromSuperview];        [transitionContext completeTransition:YES];    }];}

使用动画

1、让 FirstViewController 遵守 UIViewControllerTransitioningDelegate 协议，并将 self.transitioningDelegate 设置为 self。

self.transitioningDelegate = self;

2、实现 UIViewControllerTransitioningDelegate 协议的两个方法，用来指定动画类。

// present动画- (id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source{    return [[PresentTransition alloc] init];}

3、在present按钮的点击方法中，必须把SecondViewController的transitioningDelegate也设置为self，让ViewController管理SecondViewController的动画

- (void)presentClick{    SecondViewController * secondVC = [[SecondViewController alloc] init];    secondVC.transitioningDelegate = self; // 必须second同样设置delegate才有动画    [self presentViewController:secondVC animated:YES completion:^{    }];}

自定义Present动画完成