如何完成交互式UIViewController转换？

我一直在尝试使用新的iOS 7自定义转换API，并查看了我能找到的所有教程/文档，但我似乎无法根据我的具体情况计算出这些内容 .

基本上我正在尝试实现的是一个视图上的UIPanGestureRecognizer，我将向上滑动并转换到VC，当我将手指向上移动时，当视图从底部向上滑动时VC会向上滑动 .

没有交互过渡，我没有遇到任何问题，但是一旦我实现了交互（平移手势），我似乎无法完成转换 .

Here's the relevant code from the VC that conforms to the UIViewControllerTransitionDelegate which is needed to vend the animator controllers:

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender {
    if ([segue.identifier isEqualToString:@"Swipe"]) {
        NSLog(@"PREPARE FOR SEGUE METHOD CALLED");

        UIViewController *toVC = segue.destinationViewController;
        [interactionController wireToViewController:toVC];
        toVC.transitioningDelegate = self;
        toVC.modalPresentationStyle = UIModalPresentationCustom;
      }
}

#pragma mark UIViewControllerTransition Delegate Methods

- (id <UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:  (UIViewController *)presented                                                                   presentingController:  (UIViewController *)presenting sourceController:(UIViewController *)source {
    NSLog(@"PRESENTING ANIMATION CONTROLLER CALLED");

    SwipeDownPresentationAnimationController *transitionController = [SwipeDownPresentationAnimationController new];
    return transitionController;
}

- (id <UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed {
    NSLog(@"DISMISS ANIMATION CONTROLLER CALLED");

    DismissAnimatorViewController *transitionController = [DismissAnimatorViewController new];
    return transitionController;
}

- (id <UIViewControllerInteractiveTransitioning>)interactionControllerForDismissal:(id <UIViewControllerAnimatedTransitioning>)animator {
    NSLog(@"Interaction controller for dimiss method caled");

    return interactionController.interactionInProgress ? interactionController:nil;
}

NOTE: The interaction swipe is only for the dismissal of the VC which is why it's in the interactionControllerForDismissal method

Here's the code for the animator of the dismissal which works fine when I tap on a button to dismiss it:

#import "DismissAnimatorViewController.h"

@implementation DismissAnimatorViewController

- (NSTimeInterval)transitionDuration:(id <UIViewControllerContextTransitioning>)transitionContext {
    return 1.0;
}

- (void)animateTransition:(id <UIViewControllerContextTransitioning>)transitionContext {
    NSTimeInterval duration = [self transitionDuration:transitionContext];

    UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];

    CGRect initialFrameFromVC = [transitionContext initialFrameForViewController:fromVC];

    UIView *containerView = [transitionContext containerView];

    CGRect screenBounds = [[UIScreen mainScreen] bounds];
    NSLog(@"The screen bounds is :%@", NSStringFromCGRect(screenBounds));
    toVC.view.frame = CGRectOffset(initialFrameFromVC, 0, screenBounds.size.height);
    toVC.view.alpha = 0.2;

    CGRect pushedPresentingFrame = CGRectOffset(initialFrameFromVC, 0, -screenBounds.size.height);

    [containerView addSubview:toVC.view];

    [UIView animateWithDuration:duration
                          delay:0
         usingSpringWithDamping:0.6
          initialSpringVelocity:0
                        options:UIViewAnimationOptionCurveEaseIn
                     animations:^{
                         fromVC.view.frame = pushedPresentingFrame;
                         fromVC.view.alpha = 0.2;
                         toVC.view.frame = initialFrameFromVC;
                         toVC.view.alpha = 1.0;
                     } completion:^(BOOL finished) {
                         [transitionContext completeTransition:YES];
                     }];
}

@end

Here's the code for the UIPercentDrivenInteractiveTransition subclass which serves as the interaction controller:

#import "SwipeInteractionController.h"

@implementation SwipeInteractionController {
    BOOL _shouldCompleteTransition;
    UIViewController *_viewController;
}

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

- (void)prepareGestureRecognizerInView:(UIView*)view {
    UIPanGestureRecognizer *gesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handleGesture:)];
    gesture.minimumNumberOfTouches = 1.0;

    [view addGestureRecognizer:gesture];
}

- (CGFloat)completionSpeed {
    return 1 - self.percentComplete;
    NSLog(@"PERCENT COMPLETE:%f",self.percentComplete);
}

- (void)handleGesture:(UIPanGestureRecognizer*)gestureRecognizer {
//    CGPoint translation = [gestureRecognizer translationInView:gestureRecognizer.view.superview];
    CGPoint translation = [gestureRecognizer translationInView:gestureRecognizer.view.superview];

    switch (gestureRecognizer.state) {
        case UIGestureRecognizerStateBegan:
            // 1. Start an interactive transition!
            self.interactionInProgress = YES;
            [_viewController dismissViewControllerAnimated:YES completion:nil];
            break;
        case UIGestureRecognizerStateChanged: {
            // 2. compute the current position
            CGFloat fraction = fabsf(translation.y / 568);
            NSLog(@"Fraction is %f",fraction);
            fraction = fminf(fraction, 1.0);
            fraction = fmaxf(fraction, 0.0);
            // 3. should we complete?
            _shouldCompleteTransition = (fraction > 0.23);
            // 4. update the animation controller
            [self updateInteractiveTransition:fraction];
            NSLog(@"Percent complete:%f",self.percentComplete);
            break;
        }
        case UIGestureRecognizerStateEnded:
        case UIGestureRecognizerStateCancelled: {
            // 5. finish or cancel
            NSLog(@"UI GESTURE RECOGNIZER STATE CANCELED");
            self.interactionInProgress = NO;
            if (!_shouldCompleteTransition || gestureRecognizer.state == UIGestureRecognizerStateCancelled) {
                [self cancelInteractiveTransition];
                NSLog(@"Interactive Transition is cancled.");
                }
            else {
                NSLog(@"Interactive Transition is FINISHED");
                [self finishInteractiveTransition];
            }
            break;
        }
        default:
            NSLog(@"Default is being called");
            break;
    }
}

@end

Once again, when I run the code now and I don't swipe all the way to purposefully cancel the transition, I just get a flash and am presented with the view controller I want to swipe to. This happens regardless if the transition completes or is canceled.

However, when I dismiss via the button I get the transition specified in my animator view controller.