自定义可交互的转场动画

自定义转场动画主要有以下步骤

• 自定义导航栏
• 自定义跳转动画
• 实现交互(UIPercentDrivenInteractiveTransition协议)

1. 自定义导航栏：自定义导航栏需要遵守协议，该协议主要有如下两个方法

   // 该方法返回导航跳转时的动画，如果返回nil，则是系统默认的跳转动画，并且通过operation来判断当前执行push还是pop
   -(id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController
                                    animationControllerForOperation:(UINavigationControllerOperation)operation
                                                 fromViewController:(UIViewController *)fromVC
                                                   toViewController:(UIViewController *)toVC
   {
       return nil;
   }
   
   // 该方法返回自定义交互动画，只有实现该协议，才能在跳转时实现与用户交互
   -(id<UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController *)navigationController
                           interactionControllerForAnimationController:(id<UIViewControllerAnimatedTransitioning>)animationController
   {
       return nil;
   }

2. 自定义跳转动画：自定义跳转动画需要遵守协议，该协议主要实现下面的方法

   // 该方法返回动画执行的时间，transitionContext由系统获取
   -(NSTimeInterval)transitionDuration:(id<UIViewControllerContextTransitioning>)transitionContext
   {
       return 0.3;
   }
   
   // 通过该协议，获取跳转的两个VC
   -(void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
   {
       UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
       UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
       [self animateTransition:transitionContext fromVC:fromVC toVC:toVC fromView:fromVC.view toView:toVC.view];
   }
   
   // 这是模仿系统导航跳转的例子
   - (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
                      fromVC:(UIViewController *)fromVC
                        toVC:(UIViewController *)toVC
                    fromView:(UIView *)fromView toView:(UIView *)toView
   {
       [[transitionContext containerView] addSubview:toView];
       if (_isPush) {
           [[transitionContext containerView] bringSubviewToFront:toView];
           toView.transform = CGAffineTransformMakeTranslation(-toView.bounds.size.width, 0);
       } else {
           [[transitionContext containerView] bringSubviewToFront:fromView];
       }
       [UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
           if (_isPush) {
                 toView.transform = CGAffineTransformIdentity;
           } else {
                 fromView.transform = CGAffineTransformMakeTranslation(-fromView.bounds.size.width, 0);
           }
       } completion:^(BOOL finished) {
           transitionContext completeTransition:![transitionContext transitionWasCancelled]];
       }];
   }

3. 实现交互：自定义一个继承自UIPercentDrivenInteractiveTransition的类，它遵守协议，我们可以告诉它当前转场动画进行的百分比，它再来更新动画的进度。转场动画进行的百分比可以通过手势来计算

   // 1.在view上加入pan手势
   UIPanGestureRecognizer *gesture = objc_getAssociatedObject(self.interactiveVC.view, (__bridge const void *)(kpanGestureKey));
   if (gesture) {
       [self.interactiveVC.view removeGestureRecognizer:gesture];
   }
   gesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePanGesture:)];
   [self.interactiveVC.view addGestureRecognizer:gesture];
   objc_setAssociatedObject(self.interactiveVC.view, (__bridge const void *)(kpanGestureKey), gesture,OBJC_ASSOCIATION_RETAIN_NONATOMIC);
   
   // 2.当pan手势移动，通过移动的距离来计算当前跳转动画需要完成的百分比，当手势结束时，判断动画完成的百分比
   // 如果>50%，finishInteractiveTransition完成跳转动画
   // 如果<50%，cancelInteractiveTransition取消动画，返回原样
   case UIGestureRecognizerStateChanged:
   CGFloat fraction = point.x / [[UIScreen mainScreen] bounds].size.width;
   fraction = fminf(fmaxf(fraction, 0.0), 1.0);
   self.shouldComplete = (fraction > 0.5);
   [self updateInteractiveTransition:fraction];
   break;
   case UIGestureRecognizerStateEnded:
   case UIGestureRecognizerStateCancelled:
   self.interactioning = NO;
   if (!self.shouldComplete || pan.state == UIGestureRecognizerStateCancelled) {
         [self cancelInteractiveTransition];
   }else {
         [self finishInteractiveTransition];
   }
   break;

4. 最后附上Demo的地址：https://github.com/cdcyd/CommonControlsCollection