iOS7之定制View Controller切换效果

在iOS5和iOS6前，View Controller的切换主要有4种：

• 1. Push/Pop，NavigationViewController常干的事儿
• 2. Tab，TabViewController点击
• 3. Present Modal，调用ViewController的presentViewController:animated:completion:方法
• 4. Add ChildViewController，调用- (void)addChildViewController:(UIViewController *)childController方法

在使用Add ChildViewController的方式时，一般使用transitionFromViewController:toViewController:…的Animation block中可以实现一些简单的切换效果，这样做有2大不足：

• 1. 代码高度耦合，VC切换部分的代码直接写在container中，难以分离重用；
• 2. 支持的切换效果比较有限，因为其只能使用UIView动画来切换，管理起来也略显麻烦

于是，苹果在iOS7中引入了一些新的API来帮助开发者更容易，更松耦合地定义ViewController的转换效果。

知识点


用法
从上面的知识点图中可以看出，新的API主要提供了2种VC切换的方式，一种是动画式切换，即定义一种从一个VC到另一个VC的动画效果，切换的时候自动播放，第二种是交互式切换，这种方式同样需要定义动画效果，只是这个动画效果会根据跟随交互式手势来切换VC并同时播放动画效果。 这两种方式的用法略有不同。

动画式切换

• 首先定义一个动画类实现接口UIViewControllerAnimatedTransitioning， 实现接口的2个方法，一个是动画效果的时间，一个是动画效果（- (void)animateTransition:(id )transitionContext ），实现动画效果时可以从参数transitionContext中获取到切换时的上下文信息，比方说从哪个VC切换到哪个VC等。
• 在需切换的VC中实现UIViewControllerTransitioningDelegate，并实现animationController*方法，返回一个步骤1定义的动画变量。
• 调用展现VC切换方法，presentViewController等。

交互式切换

• 定义一个类实现接口UIViewControllerInteractiveTransitioning，iOS7提供了一个默认的基于百分比的动画实现UIPercentDrivenInteractiveTransition，大家不想太麻烦可以直接扩展这个类。该类需要绑定需要实现手势控制的VC，同时把手势操作添加到该VC上，然后在处理手势动作的时候，调用接口中的方法去更新当前的动画进度。
• 定以切换时的动画效果类。和动画式切换的方式一致
• 在需切换的VC中实现UIViewControllerTransitioningDelegate，实现interactiveController方法，返回步骤1定义的类，实现animationController方法返回步骤2定义的动画效果。

实战
下图是我实现的一个VC切换的效果图，（注：App图片是网上随便找的，不代表个人喜好：）


实现代码：
VC跳入动画的代码:

-(NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext
{
    return 0.5f;
}

-(void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{

    //Create the differents 3D animations
    CATransform3D viewFromTransform;
    CATransform3D viewToTransform;
    
    UIView *generalContentView = [transitionContext containerView];
    UIView *fromView = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey].view;
    UIView *toView = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey].view;

    
    viewFromTransform = CATransform3DMakeRotation(ROTATION_ANGLE, 0.0, 1.0, 0.0);
    viewToTransform = CATransform3DMakeRotation(-ROTATION_ANGLE, 0.0, 1.0, 0.0);
    [toView.layer setAnchorPoint:CGPointMake(0, 0.5)];
    [fromView.layer setAnchorPoint:CGPointMake(1, 0.5)];
    
//    [generalContentView setTransform:CGAffineTransformMakeTranslation(generalContentView.frame.size.width/2.0, 0)];
    
    viewFromTransform.m34 = PERSPECTIVE;
    viewToTransform.m34 = PERSPECTIVE;
    
    toView.layer.transform = viewToTransform;
    

    //Add the to- view
    [generalContentView addSubview:toView];
    
    [UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
        [generalContentView setTransform:CGAffineTransformMakeTranslation(-generalContentView.frame.size.width/2.0, 0)];
        
        fromView.layer.transform = viewFromTransform;
        toView.layer.transform = CATransform3DIdentity;
        
    } completion:^(BOOL finished) {
        
        //Set the final position of every elements transformed
        [generalContentView setTransform:CGAffineTransformIdentity];
        fromView.layer.transform = CATransform3DIdentity;
        toView.layer.transform = CATransform3DIdentity;
        [fromView.layer setAnchorPoint:CGPointMake(0.5f, 0.5f)];
        [toView.layer setAnchorPoint:CGPointMake(0.5f, 0.5f)];
        
        
        if ([transitionContext transitionWasCancelled]) {
            [toView removeFromSuperview];
        } else {
            [fromView removeFromSuperview];
        }
        
        // inform the context of completion
        [transitionContext completeTransition:![transitionContext transitionWasCancelled]];
        
    }];
}

手势交互代码：

-(void)wireToViewController:(UIViewController *)viewController
{
    self.presentingVC = viewController;
    [self prepareGestureRecognizerInView:viewController.view];
}

- (void)prepareGestureRecognizerInView:(UIView*)view {
    UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handleGesture:)];
    [view addGestureRecognizer:gesture];
}

-(CGFloat)completionSpeed
{
    return 1 - self.percentComplete;
}

- (void)handleGesture:(UIPanGestureRecognizer *)gestureRecognizer {
    CGPoint translation = [gestureRecognizer translationInView:gestureRecognizer.view.superview];
    switch (gestureRecognizer.state) {
        case UIGestureRecognizerStateBegan:
            // 1. Mark the interacting flag. Used when supplying it in delegate.
            self.interacting = YES;
            [self.presentingVC dismissViewControllerAnimated:YES completion:nil];
            break;
        case UIGestureRecognizerStateChanged: {
            // 2. Calculate the percentage of guesture
            CGFloat fraction = -translation.x / 300.0;
            //Limit it between 0 and 1
            fraction = fminf(fmaxf(fraction, 0.0), 1.0);
            self.shouldComplete = (fraction > 0.5);
            
            [self updateInteractiveTransition:fraction];
            break;
        }
        case UIGestureRecognizerStateEnded:
        case UIGestureRecognizerStateCancelled: {
            // 3. Gesture over. Check if the transition should happen or not
            self.interacting = NO;
            if (!self.shouldComplete || gestureRecognizer.state == UIGestureRecognizerStateCancelled) {
                [self cancelInteractiveTransition];
            } else {
                [self finishInteractiveTransition];
            }
            break;
        }
        default:
            break;
    }
}

根据手势3D切换的动画代码：

-(NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext
{
    return 0.5f;
}

-(void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{

    //Create the differents 3D animations
    CATransform3D viewFromTransform;
    CATransform3D viewToTransform;
    
    UIView *generalContentView = [transitionContext containerView];
    UIView *fromView = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey].view;
    UIView *toView = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey].view;

    
    viewFromTransform = CATransform3DMakeRotation(ROTATION_ANGLE, 0.0, 1.0, 0.0);
    viewToTransform = CATransform3DMakeRotation(-ROTATION_ANGLE, 0.0, 1.0, 0.0);
    [toView.layer setAnchorPoint:CGPointMake(0, 0.5)];
    [fromView.layer setAnchorPoint:CGPointMake(1, 0.5)];
    
//    [generalContentView setTransform:CGAffineTransformMakeTranslation(generalContentView.frame.size.width/2.0, 0)];
    
    viewFromTransform.m34 = PERSPECTIVE;
    viewToTransform.m34 = PERSPECTIVE;
    
    toView.layer.transform = viewToTransform;
    

    //Add the to- view
    [generalContentView addSubview:toView];
    
    [UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
        [generalContentView setTransform:CGAffineTransformMakeTranslation(-generalContentView.frame.size.width/2.0, 0)];
        
        fromView.layer.transform = viewFromTransform;
        toView.layer.transform = CATransform3DIdentity;
        
    } completion:^(BOOL finished) {
        
        //Set the final position of every elements transformed
        [generalContentView setTransform:CGAffineTransformIdentity];
        fromView.layer.transform = CATransform3DIdentity;
        toView.layer.transform = CATransform3DIdentity;
        [fromView.layer setAnchorPoint:CGPointMake(0.5f, 0.5f)];
        [toView.layer setAnchorPoint:CGPointMake(0.5f, 0.5f)];
        
        
        if ([transitionContext transitionWasCancelled]) {
            [toView removeFromSuperview];
        } else {
            [fromView removeFromSuperview];
        }
        
        // inform the context of completion
        [transitionContext completeTransition:![transitionContext transitionWasCancelled]];
        
    }];
}

待切换的VC的动画效果配置代码：

-(IBAction)changeViewController:(id)sender
{
    ToViewController *vc =[[ToViewController alloc] init];
    vc.delegate = self;
    vc.transitioningDelegate = self;
    [self.interactionAnimation wireToViewController:vc];
    [self presentViewController:vc animated:YES completion:nil];
}

-(void) didClickedDismissButton:(ToViewController *)viewController
{
    [self dismissViewControllerAnimated:YES completion:nil];
}

- (id <UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented presentingController:(UIViewController *)presenting sourceController:(UIViewController *)source
{
    return self.presentAnimation;
}

-(id <UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed
{
    return self.cubeAnimation;
}

-(id <UIViewControllerInteractiveTransitioning>)interactionControllerForDismissal:(id<UIViewControllerAnimatedTransitioning>)animator
{
    return self.interactionAnimation.interacting? self.interactionAnimation:nil;
}

整个示例的完整代码已提交到Github上：https://github.com/xianlinbox/iOS7_New/tree/master/iOS7_New/VCTransitions