Ios 为什么我的图层蒙版在[cancelInteractiveTransition]和animationDidStop:之间重置为（0,0,0,0）？

我们的应用程序的交互转换中存在一个闪烁问题，即在iOS 8上使用

UIPercentDrivenInteractiveTransition

。这似乎是因为to层的遮罩被重置（到第0帧），导致to视图被显示，即使转换被取消。。。我不知道为什么

以下是动画代码：

- (UIView *)fromView {
    UIViewController *fromVC = [self.transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    BOOL hasViewForKey = [self.transitionContext respondsToSelector:@selector(viewForKey:)]; // viewForKey is iOS8+.
    UIView *fromView = hasViewForKey ? [self.transitionContext viewForKey:UITransitionContextFromViewKey] : fromVC.view;
    return fromView;
}

- (UIView *)toView {
    UIViewController *toVC = [self.transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    BOOL hasViewForKey = [self.transitionContext respondsToSelector:@selector(viewForKey:)]; // viewForKey is iOS8+.
    UIView *toView = hasViewForKey ? [self.transitionContext viewForKey:UITransitionContextToViewKey] : toVC.view;
    return toView;
}

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

    self.transitionContext = transitionContext;

    // The container view, which, according to the docs, “acts as the superview for the views involved in the transition.”
    UIView *containerView = [transitionContext containerView];

    // The from view controller, to view controller, and final frame for the to view controller’s view are all
    // extracted from the transition context. The final frame has to be set to avoid flickering

    UIView *fromView = [self fromView];
    UIView *toView = [self toView];

    switch (self.operation) {
        case UINavigationControllerOperationPush: {
            self.viewBeingMasked = toView;
            [containerView addSubview:toView];
            break;
        }
        case UINavigationControllerOperationPop: {
            self.viewBeingMasked = fromView;
            [containerView insertSubview:toView belowSubview:fromView];
            break;
        }
        default:
            break;
    }

    // Create bezier paths used for animations start, middle and end:
    CGRect fromFrame = fromView.frame;
    CGRect maskingRect = CGRectMake(0, 0, fromFrame.size.width * kScaleFactor, fromFrame.size.height * kScaleFactor);

    UIBezierPath *startPath = [UIBezierPath bezierPathWithRect:maskingRect];

    CGAffineTransform transform = [self affineTransformToMoveMaskingRectToX:fromFrame.size.width y:(fromFrame.size.height * self.switcherHandlePosition)andHeight:self.switcherHandleHeight];
    [startPath applyTransform:transform];
    [startPath applyTransform:CGAffineTransformMakeTranslation(-self.switcherHandleHeight, 0)];

    UIBezierPath *middlePath = [startPath copy];
    CGAffineTransform horizontalTransform = CGAffineTransformMakeTranslation(-(fromFrame.size.width / 2 - self.switcherHandleHeight), 0);
    [middlePath applyTransform:horizontalTransform];

    UIBezierPath *endPath = [UIBezierPath bezierPathWithRect:maskingRect];
    [endPath applyTransform:CGAffineTransformMakeTranslation(kMaskingRectXPositionEnd, 0)];

    // other direction when popping
    if (self.operation == UINavigationControllerOperationPop) {
        UIBezierPath *tmp = startPath;
        startPath = endPath;
        endPath = tmp;
    }

    // Creates a new CAShapeLayer to represent the mask. You assign its path value with the final path after the animation
    // to avoid the layer snapping back after the animation completes...
    CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
    maskLayer.path = endPath.CGPath;
    self.viewBeingMasked.layer.mask = maskLayer;

    CAKeyframeAnimation *maskAnimation;
    maskAnimation = [self maskAnimationWithEndPath:endPath middlePath:middlePath startPath:startPath transitionContext:transitionContext];
    maskAnimation.removedOnCompletion = NO;
    [maskLayer addAnimation:maskAnimation forKey:@"path"];
}

- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag {

        // BREAKPOINT 1 HERE

        if( self.transitionContext.transitionWasCancelled ) {
            NSAssert(self.viewBeingMasked == [self toView], @"TESTING");
            [[self toView] removeFromSuperview];
            [[self.transitionContext containerView] addSubview:[self fromView]];
        }

        [self.transitionContext completeTransition:!self.transitionContext.transitionWasCancelled];
        self.viewBeingMasked.layer.mask = nil;
}

发生的情况是，在

finishInteractiveTransition

和

cancelInteractiveTransition

之间的某个地方，掩码被重置：如果我在“断点1”处中断，我会看到

self.viewBeingMasked.layer.mask

存在，但有帧（0,0,0）。我希望它有一个表示端点的帧（CGPath endPath）

是什么杀死了我的面具？我该如何修复？谢谢你的帮助

    case UIGestureRecognizerStateEnded:
        if ([self completionProgress:gestureRecognizer] >= 0.5) {
            [self.interactionController finishInteractiveTransition];
        } else {
            [self.interactionController cancelInteractiveTransition];
        }