iOS 模态动画3

效果：

11月-09-2017 10-22-43.gif

主要用到了物理引擎。

新建动画类MJAinimationRect
在头文件中声明下面两个属性，一个是动画上下文，一个是物理引擎

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
@interface MJAnimationRect : NSObject<UIViewControllerAnimatedTransitioning,UICollisionBehaviorDelegate>
@property (strong , nonatomic) id < UIViewControllerContextTransitioning > transitionContext;
@property (nonatomic, strong) UIDynamicAnimator *animator;
@end

在实现文件中完成两个代理相对应该实现的代理方法

动画过度时间，直接返回时间值

-(NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext
{
    return 2.0f;
}

之后准备实现动画效果，代码如下
1.通过上下文获取跳转的view
2.将fromVC截图
3.调用cutView方法将截图切成4*5点格子并添加到当前的containerView上
4.添加之前随机对切图进行微角度旋转，以增加动画效果
5.获取目标view并添加到界面，置于页面底部，暂时先把他的alpha置为0
6.添加作用力
7.设置碰撞检测

-(void)AnimationAnimationType:(id<UIViewControllerContextTransitioning>)transitionContext andToVC:(UIViewController*)toVC andFromVC:(UIViewController*)fromVC
{
    UIView *containerView = [transitionContext containerView];
    UIView *mainSnap = [fromVC.view snapshotViewAfterScreenUpdates:NO];
    NSMutableArray* cutViewArray = [self cutView:mainSnap intoSlicesOfWidth:mainSnap.frame.size.width/kwidthCount andHeight:mainSnap.frame.size.height/kHeightCount];
    for (int i=0; i<cutViewArray.count; i++) {
        UIView* cutView = (UIView*)cutViewArray[i];
        
        CGFloat angle = (i% 2 ? 1 : -1) * (rand() % 5 / 10.0);
        cutView.transform = CGAffineTransformMakeRotation(angle);
        [containerView addSubview:cutView];
    }
    UIView* toView = [toVC view];
    toView.frame = [transitionContext finalFrameForViewController:toVC];
    [containerView addSubview:toView];
    [containerView sendSubviewToBack:toView];
    toView.alpha = 0;
    
    //截图已经覆盖fromView.view 所以可以直接隐藏。
    fromVC.view.hidden = YES;

    self.animator = [[UIDynamicAnimator alloc] initWithReferenceView:containerView];
    UIDynamicBehavior *behaviour = [[UIDynamicBehavior alloc] init];
    //为每个view添加重力
    UIGravityBehavior* gravity = [[UIGravityBehavior alloc] initWithItems:cutViewArray];
    gravity.gravityDirection = CGVectorMake(0, 1); // 方向
    gravity.magnitude = 5; //加速度
    // 碰撞检测
    UICollisionBehavior *collision = [[UICollisionBehavior alloc] initWithItems:cutViewArray];
    // 设置不要出边界，碰到边界会被反弹
    collision.translatesReferenceBoundsIntoBoundary = YES;
    collision.collisionDelegate = self;
    //除了边界碰撞没有其他碰撞
    collision.collisionMode = UICollisionBehaviorModeBoundaries;
    [behaviour addChildBehavior:gravity];
    [behaviour addChildBehavior:collision];
    
    //每个view设置不同的动画效果，添加到总的动作中去
    for (UIView *aView in cutViewArray) {
        UIDynamicItemBehavior *itemBehaviour = [[UIDynamicItemBehavior alloc] initWithItems:@[aView]];
        itemBehaviour.elasticity = (rand() % 5) / 8.0;
        itemBehaviour.density = (rand() % 5 / 3.0);
                itemBehaviour.allowsRotation = YES;
        [behaviour addChildBehavior:itemBehaviour];
    }
    [self.animator addBehavior:behaviour];
    
    [UIView animateWithDuration:2 animations:^{
        for (UIView *aView in cutViewArray) {
            aView.alpha = 0.0;
            toView.alpha = 1;
        }
    } completion:^(BOOL finished) {
        for (UIView *view in cutViewArray) {
            [view removeFromSuperview];
        }
        [cutViewArray removeAllObjects];
        fromVC.view.hidden = NO;
        [transitionContext completeTransition:YES];
    }];
    
}

-(NSMutableArray *)cutView:(UIView *)view intoSlicesOfWidth:(float)width andHeight:(float)height{
    NSMutableArray *lineViews = [NSMutableArray array];
    UIView *subsnapshot;
    for (int x=0; x<CGRectGetWidth(view.frame); x+=width) {
        for (int y=0;y<CGRectGetHeight(view.frame); y+=height) {
            CGRect subrect = CGRectMake(x, y, width, height);
            subsnapshot = nil;
            subsnapshot = [view resizableSnapshotViewFromRect:subrect afterScreenUpdates:YES withCapInsets:UIEdgeInsetsZero];
            subsnapshot.frame = subrect;
            [lineViews addObject:subsnapshot];
        }
    }
    return lineViews;
}

之后在另外一个代理方法中调用该方法

-(void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{
    self.transitionContext = transitionContext;
    UIViewController* toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UIViewController* fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    [self AnimationAnimationType:transitionContext andToVC:toVC andFromVC:fromVC];
}

- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag{
    [self.transitionContext completeTransition:![self.transitionContext transitionWasCancelled]];
    [self.transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey].view.layer.mask = nil;
    [self.transitionContext viewControllerForKey:UITransitionContextToViewControllerKey].view.layer.mask = nil;
}

调用方法，import 该类

实现以下方法即可

//返回一个管理动画过渡的对象
-(nullable id <UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source
{
    if (!self.animationRect) {
        self.animationRect = [MJAnimationRect new];
    }
    return self.animationRect;
}

- (nullable id <UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed{
    if(!self.animationRect){
        self.animationRect = [[MJAnimationRect alloc] init];
    }
    return self.animationRect;
}