iOS7之定製View Controller切換效果

原文地址：iOS7之定製View Controller切換效果

在iOS5和iOS6前，View Controller的切換主要有4種： 

• 1. Push/Pop，NavigationViewController常乾的事兒
• 2. Tab，TabViewController點擊
• 3. Present Modal，調用ViewController的presentViewController:animated:completion:方法
• 4. Add ChildViewController，調用- (void)addChildViewController:(UIViewController *)childController方法

在使用Add ChildViewController的方式時，一般使用transitionFromViewController:toViewController:…的Animation block中可以實現一些簡單的切換效果，這樣做有2大不足： 

• 1. 代碼高度耦合，VC切換部分的代碼直接寫在container中，難以分離重用；
• 2. 支持的切換效果比較有限，因爲其只能使用UIView動畫來切換，管理起來也略顯麻煩

於是，蘋果在iOS7中引入了一些新的API來幫助開發者更容易，更鬆耦合地定義ViewController的轉換效果。 

知識點 


用法 
從上面的知識點圖中可以看出，新的API主要提供了2種VC切換的方式，一種是動畫式切換，即定義一種從一個VC到另一個VC的動畫效果，切換的時候自動播放，第二種是交互式切換，這種方式同樣需要定義動畫效果，只是這個動畫效果會根據跟隨交互式手勢來切換VC並同時播放動畫效果。 這兩種方式的用法略有不同。 

動畫式切換 

• 首先定義一個動畫類實現接口UIViewControllerAnimatedTransitioning， 實現接口的2個方法，一個是動畫效果的時間，一個是動畫效果（- (void)animateTransition:(id )transitionContext ），實現動畫效果時可以從參數transitionContext中獲取到切換時的上下文信息，比方說從哪個VC切換到哪個VC等。
• 在需切換的VC中實現UIViewControllerTransitioningDelegate，並實現animationController*方法，返回一個步驟1定義的動畫變量。
• 調用展現VC切換方法，presentViewController等。

交互式切換 

• 定義一個類實現接口UIViewControllerInteractiveTransitioning，iOS7提供了一個默認的基於百分比的動畫實現UIPercentDrivenInteractiveTransition，大家不想太麻煩可以直接擴展這個類。該類需要綁定需要實現手勢控制的VC，同時把手勢操作添加到該VC上，然後在處理手勢動作的時候，調用接口中的方法去更新當前的動畫進度。
• 定以切換時的動畫效果類。和動畫式切換的方式一致
• 在需切換的VC中實現UIViewControllerTransitioningDelegate，實現interactiveController方法，返回步驟1定義的類，實現animationController方法返回步驟2定義的動畫效果。

實戰 
下圖是我實現的一個VC切換的效果圖，（注：App圖片是網上隨便找的，不代表個人喜好：） 
 

實現代碼： 
VC跳入動畫的代碼: 

-(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]];

    }];
}

手勢交互代碼： 

-(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;
    }
}

根據手勢3D切換的動畫代碼： 

-(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]];

    }];
}

待切換的VC的動畫效果配置代碼： 

-(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;
}

整個示例的完整代碼已提交到Github上：https://github.com/xianlinbox/iOS7_New/tree/master/iOS7_New/VCTransitions