6.系统转场动画

系统转场动画

CATransition *transition = [CATransition animation];
    transition.duration = 0.7;
    transition.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    // 过渡动画种类
    //淡化、推挤、揭开、覆盖{kCATransitionFromLeft, kCATransitionFromRight, kCATransitionFromTop, kCATransitionFromBottom}
    //立方体、吸收、翻转、波纹、翻页、反翻页、镜头开、镜头关{@"cube",@"suckEffect",@"oglFlip",@"rippleEffect",@"pageCurl",@"pageUnCurl",@"cameraIrisHollowOpen",@"cameraIrisHollowClose"}
    transition.type = @"cube";

    // 过渡方向
    transition.subtype = kCATransitionFromLeft;//{kCATransitionFromLeft, kCATransitionFromRight, kCATransitionFromTop, kCATransitionFromBottom};
    // 哪个控制器实现转场，哪个控制器添加动画
    [self.navigationController.view.layer addAnimation:transition forKey:nil];

转场动画的使用准则就是：Push/Pop 时重载UINavigationControllerDelegate 的⽅法； Modal 时重载UIViewControllerTransitioningDelegate 的⽅法

UINavigationControllerDelegate （Push/Pop）

在需要实现动画的控制器中，实现 navigationController:animationControllerForOperation:fromViewController:toViewController:函数并返回一个遵守UIViewControllerAnimatedTransitioning协议的NSObject对象，如果Push/Pop都要添加动画，那么通过operation == UINavigationControllerOperationPush 、operation == UINavigationControllerOperationPop 区分，并返回不同的对象

1. UIViewControllerContextTransitioning
   • 保存转场上下文，动画结束后移除遮罩
   • 编辑转场上下文containerView
   • 通过核心动画path，设置两个遮罩的值（跳转按钮遮罩、可以覆盖整个屏幕的遮罩）

- (NSTimeInterval)transitionDuration:(id <UIViewControllerContextTransitioning>)transitionContext{
    return  0.7f;
}

- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext{
    
    // 保存转场上下文
    self.transitionContext = transitionContext;

    // 根据上下文的Key获取发生转场的两个控制器
    ViewController * fromVC = (ViewController *)[transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    SecondViewController *toVC = (SecondViewController *)[transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    
    // 获取上下文containerView
    UIView *contView = [transitionContext containerView];
    [contView addSubview:fromVC.view];
    [contView addSubview:toVC.view];

    UIButton *button = fromVC.button;
    
    UIBezierPath *maskStartBP =  [UIBezierPath bezierPathWithOvalInRect:button.frame];

    //创建两个圆形的 UIBezierPath 实例；一个是 button 的 size ，另外一个则拥有足够覆盖屏幕的半径。最终的动画则是在这两个贝塞尔路径之间进行的
    CGPoint finalPoint;
    //判断触发点在那个象限
    if(button.frame.origin.x > (toVC.view.bounds.size.width / 2)){
        if (button.frame.origin.y < (toVC.view.bounds.size.height / 2)) {
            //第一象限
            finalPoint = CGPointMake(button.center.x - 0, button.center.y - CGRectGetMaxY(toVC.view.bounds)+30);
        }else{
            //第四象限
            finalPoint = CGPointMake(button.center.x - 0, button.center.y - 0);
        }
    }else{
        if (button.frame.origin.y < (toVC.view.bounds.size.height / 2)) {
            //第二象限
            finalPoint = CGPointMake(button.center.x - CGRectGetMaxX(toVC.view.bounds), button.center.y - CGRectGetMaxY(toVC.view.bounds)+30);
        }else{
            //第三象限
            finalPoint = CGPointMake(button.center.x - CGRectGetMaxX(toVC.view.bounds), button.center.y - 0);
        }
    }
    // 不同象限 对应不同对角，计算能够遮罩住屏幕的圆
    CGFloat radius = sqrt((finalPoint.x * finalPoint.x) + (finalPoint.y * finalPoint.y));
    UIBezierPath *maskFinalBP = [UIBezierPath bezierPathWithOvalInRect:CGRectInset(button.frame, -radius, -radius)];
    
    //创建一个 CAShapeLayer 来负责展示圆形遮盖
    CAShapeLayer *maskLayer = [CAShapeLayer layer];
    maskLayer.path = maskFinalBP.CGPath; //将它的 path 指定为最终的 path 来避免在动画完成后会回弹
    toVC.view.layer.mask = maskLayer;
    
    CABasicAnimation *maskLayerAnimation = [CABasicAnimation animationWithKeyPath:@"path"];
    maskLayerAnimation.fromValue = (__bridge id)(maskStartBP.CGPath);
    maskLayerAnimation.toValue = (__bridge id)((maskFinalBP.CGPath));
    maskLayerAnimation.duration = [self transitionDuration:transitionContext];
    maskLayerAnimation.timingFunction = [CAMediaTimingFunction  functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
    maskLayerAnimation.delegate = self;
    
    [maskLayer addAnimation:maskLayerAnimation forKey:@"path"]; 
}

2. CAAnimationDelegate

- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag{

    [self.transitionContext completeTransition:![self. transitionContext transitionWasCancelled]];
    //清除 fromVC 的 mask
    [self.transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey].view.layer.mask = nil;
    [self.transitionContext viewControllerForKey:UITransitionContextToViewControllerKey].view.layer.mask = nil;
}