objective-c - 为什么 iOS7 的 animateTransition 中的 UIView transitionFromView 可以，但 iOS8 没有动画

Question

我想在 presentViewController 期间制作动画:

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext {
    UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UIView *toView = toVC.view;
    UIView *fromView = fromVC.view;
    UIView* containerView = [transitionContext containerView];
    [containerView addSubview:toView];
    NSTimeInterval duration = 0.35;
    [UIView transitionFromView:fromView toView:toView duration:duration options:(self.reverse?UIViewAnimationOptionTransitionFlipFromLeft:UIViewAnimationOptionTransitionFlipFromRight) | 
    UIViewAnimationOptionAllowUserInteraction completion:^(BOOL finished) {
        [transitionContext completeTransition:![transitionContext transitionWasCancelled]];
    }];
}

这在 iOS7 上工作正常，但在 iOS8 上没有动画。

Answer 1

+transitionFromView:toView:duration:options:completion:处理 View 层次结构的工作。你不应该需要 [containerView addSubview:toView]。

+transitionFromView:toView:duration:options:completion: 内部的某处应该是以下代码:

UIView *superview = fromView.superview;
[fromView removeFromSuperview];
[superview addSubview:toView];

您是否尝试过删除 containerView 代码:

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext {
    UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UIView *toView = toVC.view;
    UIView *fromView = fromVC.view;
    NSTimeInterval duration = 0.35;
    [UIView transitionFromView:fromView toView:toView duration:duration options:(self.reverse?UIViewAnimationOptionTransitionFlipFromLeft:UIViewAnimationOptionTransitionFlipFromRight) | 
    UIViewAnimationOptionAllowUserInteraction completion:^(BOOL finished) {
        [transitionContext completeTransition:![transitionContext transitionWasCancelled]];
    }];
}