但是,有时候,我会在结尾再加点一些令人分心的动画(似乎重复动画的后半部分).使用相当简单的动画,我很少在iPhone 5上看到这种症状(虽然我在慢速笔记本电脑上工作时经常在模拟器上看到它).如果我使动画在计算上更加昂贵(例如大量的阴影,多个视图动画化不同的方向等),则设备上的这个问题的频率增加.

有没有人看到这个问题,并找出一个解决方案,而不是简化动画(我承认应该做的)和/或写我自己的交互控制器？ UIPercentDrivenInteractiveTransition方法具有一定的优雅性,但是我对不确定性的行为感到不安.有人看到这个行为吗？有没有人知道其他解决方案？

为了说明效果,请参见下图.注意第二场景,红色视图,动画结束时,似乎第二次重复其动画的后半部分.

此动画由以下生成：

>反复调用updateInteractiveTransition,进度从0％更新到40％;
>暂时暂停(所以你可以区分交互过渡和finishInteractiveTransition产生的完成动画);
>然后调用finishInteractiveTransition来完成动画;和
>动画控制器的动画完成块调用completeTransition的transitionContext,以便清理所有东西.

做一些诊断,似乎是最后一步触发动画的无关的一点.动画控制器的完成块在动画完成时被调用,但一旦调用completeTransition,它有时会重复动画的最后一位(特别是使用复杂动画时).

我不认为它是相关的,但这是我的配置导航控制器执行交互过渡的代码：

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.navigationController.delegate = self;

    self.interationController = [[UIPercentDrivenInteractiveTransition alloc] init];
}

- (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController
                                  animationControllerForOperation:(UINavigationControllerOperation)operation
                                               fromViewController:(UIViewController*)fromVC
                                                 toViewController:(UIViewController*)toVC
{
    if (operation == UINavigationControllerOperationPush)
        return [[PushAnimator alloc] init];

    return nil;
}

- (id <UIViewControllerInteractiveTransitioning>)navigationController:(UINavigationController*)navigationController
                          interactionControllerForAnimationController:(id <UIViewControllerAnimatedTransitioning>)animationController
{
    return self.interationController;
}

我的PushAnimator是：

@implementation PushAnimator

- (NSTimeInterval)transitionDuration:(id <UIViewControllerContextTransitioning>)transitionContext
{
    return 5.0;
}

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{
    UIViewController* toViewController   = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UIViewController* fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];

    [[transitionContext containerView] addSubview:toViewController.view];
    toViewController.view.frame = CGRectOffset(fromViewController.view.frame,fromViewController.view.frame.size.width,0);;

    [UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
        toViewController.view.frame = fromViewController.view.frame;
    } completion:^(BOOL finished) {
        [transitionContext completeTransition:![transitionContext transitionWasCancelled]];
    }];
}

@end

注意,当我将logging语句放在我称为completeTransition的位置时,我可以看到,在调用completeTransition之后,动画的这个无关的位置就会发生(即使动画在那一刻真的完成了).这将表明额外的动画可能是调用completeTransition的结果.

我已经用手势识别器完成了这个实验：

- (void)handlePan:(UIScreenEdgePanGestureRecognizer *)gesture
{
    CGFloat width = gesture.view.frame.size.width;

    if (gesture.state == UIGestureRecognizerStateBegan) {
        [self performSegueWithIdentifier:@"pushToSecond" sender:self];
    } else if (gesture.state == UIGestureRecognizerStateChanged) {
        CGPoint translation = [gesture translationInView:gesture.view];
        [self.interactionController updateInteractiveTransition:ABS(translation.x / width)];
    } else if (gesture.state == UIGestureRecognizerStateEnded ||
               gesture.state == UIGestureRecognizerStateCancelled)
    {
        CGPoint translation = [gesture translationInView:gesture.view];
        CGPoint velocity    = [gesture velocityInView:gesture.view];
        CGFloat percent     = ABS(translation.x + velocity.x * 0.25 / width);

        if (percent < 0.5 || gesture.state == UIGestureRecognizerStateCancelled) {
            [self.interactionController cancelInteractiveTransition];
        } else {
            [self.interactionController finishInteractiveTransition];
        }
    }
}

我也是通过手动调用updateInteractiveTransition和finishInteractiveTransition(从方程式中消除手势识别器)来完成的,它仍然表现出这种奇怪的行为：

[self performSegueWithIdentifier:@"pushToSecond" sender:self];

dispatch_after(dispatch_time(DISPATCH_TIME_NOW,(int64_t)(1.0 * NSEC_PER_SEC)),dispatch_get_main_queue(),^{
    [self.interactionController updateInteractiveTransition:0.40];

    dispatch_after(dispatch_time(DISPATCH_TIME_NOW,^{
        [self.interactionController finishInteractiveTransition];
    });
});

底线,我得出结论,这是一个孤立到UIPercentDrivenInteractiveTransition与复杂动画的问题.我可以通过简化它们来减少问题(例如快照和动画快照视图).我也怀疑我可以通过不使用UIPercentDrivenInteractiveTransition来解决这个问题,并且编写自己的交互控制器,这样做就可以做动画本身,而不用插入animationWithDuration块.

但是我想知道是否有人想出了使用复杂动画使用UIPercentDrivenInteractiveTransition的其他技巧.