iOS 9 自定义转换 - 未调用 animationControllerForDismissedController

Question

我是 iOS 开发的新手，最近在 iOS 9 中遇到了自定义转换的问题。

我有一个对象符合 UIViewControllerTransitioningDelegate 协议(protocol)并实现了 animationControllerForDismissedController，类似于:

@implementation MyCustomizedTransitioningDelegate

#pragma mark - UIViewControllerTransitioningDelegate

- (id<UIViewControllerAnimatedTransitioning>)animationControllerForDismissedController:(UIViewController *)dismissed
{
    MyCustomizedTransitionAnimator *animator = [[MyCustomizedTransitionAnimator alloc] init];
    animator.presenting = NO;
    return animator;
}

@end

触发模态转换的过程是这样的:

@implementation MyViewController

#pragma mark - Initializers

+ (MyCustomizedTransitioningDelegate *)modalTransitioningDelegateSingletonInstance;
{
    static MyCustomizedTransitioningDelegate *delegateInst = nil;
    static dispatch_once_t onceToken = 0;
    dispatch_once(&onceToken, ^{
        delegateInst = [[MyCustomizedTransitioningDelegate alloc] init];
    });

    return delegateInst;
}

#pragma mark - UIViewController

- (void)dismissViewControllerAnimated:(BOOL)animated completion:(void (^)(void))completion;
{
    [self prepareForDismissViewControllerAnimated:animated completion:&completion];
    [super dismissViewControllerAnimated:animated completion:completion];
}

- (void)prepareForDismissViewControllerAnimated:(BOOL)animated completion:(dispatch_block_t *)completion;
{
    self.presentedViewController.modalPresentationStyle = UIModalPresentationCustom;
    self.presentedViewController.transitioningDelegate = [[self class] modalTransitioningDelegateSingletonInstance];      
}

@end

由于没有调用animationControllerForDismissedController方法，所以没有创建MyCustomizedTransitionAnimator，导致它的animateTransition也没有被调用，从而出现意想不到的问题在我的应用程序中。 (抱歉我的英语不好...)

我还附上了 iOS8 和 iOS9 的堆栈跟踪截图。在 iOS 8 中，animationControllerForDismissedController 在下面的堆栈跟踪之后被调用。

但是在 iOS9 中，transitionDidFinish 以某种方式被提前调用，我猜这可能会阻止 animationControllerForDismissedController 被调用？

我想知道这是否是 iOS 9 的错误。任何解释或解决解决方案将不胜感激!

Answer 1

我遇到了同样的问题。

我希望这会对某人有所帮助。

为我修复的是将应用 UIViewControllerTransitioningDelegate 协议(protocol)的对象作为变量实例，以与其保持牢固的关系。

我想是因为它在第一次呈现 View 后就被取消了。