iOS自定义转场动画(push)

push.gif

iOS7 开始苹果推出了自定义转场的 API 。从此，任何可以用 CoreAnimation 实现的动画，都可以出现在两个 ViewController 的切换之间。并且实现方式高度解耦，这也意味着在保证代码干净的同时想要替换其他动画方案时只需简单改一个类名就可以了。

自定义转场动画Push

想在Push的时候实现自定义转场动画首先要遵守一个协议UINavigationControllerDelegate

苹果在 UINavigationControllerDelegate 中给出了几个协议方法，通过返回类型就可以很清楚地知道各自的具体作用。

//用来自定义转场动画
- (nullable id <UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController
                                   animationControllerForOperation:(UINavigationControllerOperation)operation
                                                fromViewController:(UIViewController *)fromVC
                                                  toViewController:(UIViewController *)toVC  NS_AVAILABLE_IOS(7_0);

//为这个动画添加用户交互

- (nullable id <UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController
                          interactionControllerForAnimationController:(id <UIViewControllerAnimatedTransitioning>) animationController NS_AVAILABLE_IOS(7_0);

在第一个方法里只要返回一个遵守UIViewControllerInteractiveTransitioning协议的对象,并在里面实现动画即可

创建继承自 NSObject 并且声明 UIViewControllerAnimatedTransitioning 的的动画类。

重载 UIViewControllerAnimatedTransitioning 中的协议方法。

//返回动画时间
- (NSTimeInterval)transitionDuration:(nullable id <UIViewControllerContextTransitioning>)transitionContext;

//将动画的代码写到里面即可
- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext;

首先自定义一个名为CustomAnimateTransitionPush的类继承于NSObject准守了UIViewControllerAnimatedTransitioning协议

self.transitionContext=transitionContext;

    // 获取动画的源控制器和目标控制器
    ViewController * fromVC = (ViewController *)[transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    PushViewController *toVC = (PushViewController *)[transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UIView *contView = [transitionContext containerView];

    UIButton *button = fromVC.button;

    UIBezierPath *maskStartBP =  [UIBezierPath bezierPathWithOvalInRect:button.frame];
    // 都添加到container中。注意顺序
    [contView addSubview:fromVC.view];
    [contView addSubview:toVC.view];


    //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);
        }
    }


    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"];

在控制器里面用来自定义转场动画的方法里返回刚才自定义的动画类

-(id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC
{

    if(operation==UINavigationControllerOperationPush)
    {
        //自定义的动画类
        CustomAnimateTransitionPush *animateTransitionPush=[CustomAnimateTransitionPush new];
        return animateTransitionPush;
    }
    else
    {
        return nil;
    }

}

到此为止自定义转场动画就完成了
pop的动画只是把push动画反过来做一遍。