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
- 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。
- 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。
- 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
- 创建一个文件继承自 NSObject，取名为PresentTransition并在.h中遵守 UIViewControllerAnimatedTransitioning协议。
- 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
- 让 FirstViewController 遵守 UIViewControllerTransitioningDelegate 协议，并将 self.transitioningDelegate 设置为 self。
self.transitioningDelegate = self;
- 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];
}
- 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:^{
}];
}
