iOS实现类似格瓦拉电影的转场动画

用过格瓦拉电影，或者其他app可能都知道，一种点击按钮用放大效果实现转场的动画现在很流行，效果大致如下

自定义转场动画

首先就要声明一个遵守UIViewControllerAnimatedTransitioning协议的类.

然后实现协议中的两个函数

// This is used for percent driven interactive transitions, as well as for container controllers that have companion animations that might need to
// 返回转场时间
- (NSTimeInterval)transitionDuration:(nullable id <UIViewControllerContextTransitioning>)transitionContext;
// 转场的动作
- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext;

push和pop都在animateTransition:里面实现，所以需要一个参数表示是push还是pop；还有一个参数表示转场时间

#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>

typedef enum : NSUInteger {
 animate_push = 0,
 animate_pop = 1,

} Animate_Type;

@interface SFTrainsitionAnimate : NSObject<UIViewControllerAnimatedTransitioning>

- (instancetype)initWithAnimateType:(Animate_Type)type andDuration:(CGFloat)dura;

@property (assign, nonatomic) CGFloat duration;
@property (assign, nonatomic) Animate_Type type;

@end

那么要如何使用新建的对象呢？可以通过UINavigationControllerDelegate中的

- (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC{
 if (operation == UINavigationControllerOperationPush) {
 self.animate = [[SFTrainsitionAnimate alloc] init];
 return self.animate;
 }else{
 return nil;
 }

}

当然，要调用这个方法还得先把UINavigationControllerDelegate委托给视图控制器

self.navigationController.delegate = self;

再来看看UIViewControllerAnimatedTransitioning这个协议，返回时间的方法就不介绍了。重点在

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext{
 //起始视图控制器
 UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
 //目标视图控制器
 UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
 //在这个视图上实现跳转动画
 UIView *containView = [transitionContext containerView];
}

如上注释，我们可以通过参数transitionContext获取到起始和目标控制。并在containView这个视图实现我们想要实现的动画。

接下来就是转场动画的实现了,push动画的流程大概就是:点击第一个页面的一个控件，模拟出控件然后移动到第二个界面同一个样式控件的位置，之后再把第二个界面以控件的位置中心扩散显示出来。

那么现在我们就在协议方法中通过fromVC获取到第一个视图的控件，并制造一个镜像视图移动到toVC的目标控件的位置。在这里，我调用了UIViewcontroller分类关联一个对象，用来记录控件（非拥有关系）。

#import <UIKit/UIKit.h>
#import <Foundation/Foundation.h>

@interface UIViewController (SFTrainsitionExtension)

@property (assign, nonatomic) CGFloat sf_targetHeight;//灰白背景的分割线高度
@property (weak , nonatomic) UIView *sf_targetView;

@end

产生targetView镜像：

//产生targetView镜像
- (UIView *)customSnapshoFromView:(UIView *)inputView {

 // Make an image from the input view.
 UIGraphicsBeginImageContextWithOptions(inputView.bounds.size, NO, 0);
 [inputView.layer renderInContext:UIGraphicsGetCurrentContext()];
 UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
 UIGraphicsEndImageContext();

 // Create an image view.
 UIView *snapshot = [[UIImageView alloc] initWithImage:image];
 snapshot.layer.masksToBounds = NO;
 snapshot.layer.cornerRadius = 0.0;
 snapshot.layer.shadowOffset = CGSizeMake(0.0, 0.0);
 snapshot.layer.shadowRadius = 5.0;
 snapshot.layer.shadowOpacity = 0.4;

 return snapshot;
}

现在就可以制作移动的动画：

//起始位置
 CGRect originFrame = [fromVC.sf_targetView convertRect:fromVC.sf_targetView.bounds toView:fromVC.view];
 //动画移动的视图镜像
 UIView *customView = [self customSnapshoFromView:fromVC.sf_targetView];
 customView.frame = originFrame;

 //移动的目标位置
 CGRect finishFrame = [toVC.sf_targetView convertRect:toVC.sf_targetView.bounds toView:toVC.view];

 UIView *containView = [transitionContext containerView];

 //背景视图 灰色高度
 CGFloat height = CGRectGetMidY(finishFrame);
 toVC.sf_targetHeight = height;

 //背景视图 灰色
 UIView *backgray = [[UIView alloc] initWithFrame:CGRectMake(0, 0, k_SF_SCREEN_WIDTH, k_SF_SCREEN_HIGHT)];
 backgray.backgroundColor = [UIColor lightGrayColor];
 //背景视图 白色
 UIView *backwhite = [[UIView alloc] initWithFrame:CGRectMake(0, height, k_SF_SCREEN_HIGHT, k_SF_SCREEN_HIGHT-height)];
 backwhite.backgroundColor = [UIColor whiteColor];

 toVC.view.frame = [transitionContext finalFrameForViewController:toVC];

 //注意添加顺序
 [containView addSubview:toVC.view];
 [containView addSubview:backgray];
 [backgray addSubview:backwhite];
 [containView addSubview:customView];

 //动画
 [UIView animateWithDuration:_duration/3 animations:^{
 customView.frame = finishFrame;
 customView.transform = CGAffineTransformMakeScale(1.1, 1.1);
 } completion:^(BOOL finished) {
 if (finished) {

  [UIView animateWithDuration:_duration/3 animations:^{

  customView.transform = CGAffineTransformIdentity;

  } completion:^(BOOL finished) {
  if (finished) {
   [UIView animateWithDuration:_duration/3 animations:^{
   customView.alpha = 0.0;
   } completion:^(BOOL finished) {
   if (finished) {
    [backgray removeFromSuperview];
    [customView removeFromSuperview];
    [transitionContext completeTransition:YES];
   }
   }];

   [self addPathAnimateWithView:backgray fromPoint:customView.center];

  }
  }];

移动完之后，要以圆形扩散显示出push之后的界面。就可以通过UIBezierPath和CAShapeLayer来实现。UIBezierPath表示路径，CAShapeLayer可以根据路径来显示区域，那么我们可以以第一个界面的视图先看看效果。

 UIBezierPath *path = [UIBezierPath bezierPathWithRect:self.collectionView.bounds];

 [path appendPath:[UIBezierPath bezierPathWithArcCenter:self.collectionView.center radius:50 startAngle:0 endAngle:2*M_PI clockwise:NO]];

 CAShapeLayer *layer = [CAShapeLayer layer];
 layer.path = path.CGPath;
 self.collectionView.layer.mask = layer;

初始化path路径以collectionView的四边画一个路径，然后加入一个以collectionView的中心为圆点，半径为50的路径，显示的区域就为两个路径之间的区域。

然后再把代码中的radius大小设为200

现在，我们创建一个CABasicAnimation对象去完成扩散的动画，起始位置是半径为10的圆，终点位置是半径为200的圆.

 UIBezierPath *path = [UIBezierPath bezierPathWithRect:self.collectionView.bounds];

 [path appendPath:[UIBezierPath bezierPathWithArcCenter:self.collectionView.center radius:10 startAngle:0 endAngle:2*M_PI clockwise:NO]];

 UIBezierPath *path2 = [UIBezierPath bezierPathWithRect:self.collectionView.bounds];

 [path2 appendPath:[UIBezierPath bezierPathWithArcCenter:self.collectionView.center radius:200 startAngle:0 endAngle:2*M_PI clockwise:NO]];

 CAShapeLayer *layer = [CAShapeLayer layer];
 self.collectionView.layer.mask = layer;

 CABasicAnimation *pathAnimation = [CABasicAnimation animationWithKeyPath:@"path"];
 pathAnimation.fromValue = (__bridge id)path.CGPath;
 pathAnimation.toValue = (__bridge id)path2.CGPath;
 pathAnimation.duration = 1.0;
 pathAnimation.repeatCount = 1;
 pathAnimation.removedOnCompletion = NO;
 pathAnimation.fillMode = kCAFillModeForwards;
 pathAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
 [layer addAnimation:pathAnimation forKey:@"pathAnimate"];

现在就可以完成push的 转场效果了。注意圆圈白色部分显示的是collectionView底部的self.view的视图。

//加入收合动画
- (void)addPathAnimateWithView:(UIView *)toView fromPoint:(CGPoint)point{
 //create path
 UIBezierPath *path = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, k_SF_SCREEN_WIDTH, k_SF_SCREEN_HIGHT)];
 //create path
 [path appendPath:[UIBezierPath bezierPathWithArcCenter:point radius:0.1 startAngle:0 endAngle:2*M_PI clockwise:NO]];

 CGFloat radius = point.y > 0?k_SF_SCREEN_HIGHT*3/4: k_SF_SCREEN_HIGHT*3/4-point.y;
 UIBezierPath *path2 = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, k_SF_SCREEN_WIDTH, k_SF_SCREEN_HIGHT)];
 [path2 appendPath:[UIBezierPath bezierPathWithArcCenter:point radius:radius startAngle:0 endAngle:2*M_PI clockwise:NO]];

 CAShapeLayer *shapeLayer = [CAShapeLayer layer];
 //shapeLayer.path = path.CGPath;
 toView.layer.mask = shapeLayer;

 CABasicAnimation *pathAnimation = [CABasicAnimation animationWithKeyPath:@"path"];
 pathAnimation.fromValue = _type == animate_push? (__bridge id)path.CGPath:(__bridge id)path2.CGPath;
 pathAnimation.toValue = _type == animate_push? (__bridge id)path2.CGPath:(__bridge id)path.CGPath;
 pathAnimation.duration = _duration/3;
 pathAnimation.repeatCount = 1;
 pathAnimation.removedOnCompletion = NO;
 pathAnimation.fillMode = kCAFillModeForwards;
 pathAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
 [shapeLayer addAnimation:pathAnimation forKey:@"pathAnimate"];
}

pop动画其实和push差不多，这里就不说了。

好了，以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作能带来一定的帮助，如果有疑问大家可以留言交流。