如何在animateTransition期间在ToViewController中获取子视图的框架:？

Question

我使用iOS 7引入的新自定义过渡,我试图将视图从我的'主'视图控制器移动到我的'详细'视图控制器中的视图,类似于Photos.app放大照片时的方式你点击它,除了详细视图中的这个视图只占用屏幕的一半.要做到这一点,我试图通过从细节或toViewController获取最终帧来将此视图设置为最终帧的动画.然而,我得到的框架是来自Interface Builder的toViewController视图的起始框架,而不是AutoLayer在其上传递后出现的视图.如何通过自动布局设置框架后获取框架？我在toViewController特殊视图框架返回animateTransition之前尝试了[self.view layoutSubviews]:但仍然给出了IB布局.

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{
    UIViewController* toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    UIViewController* fromViewController = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    [[transitionContext containerView] addSubview:toViewController.view];
    toViewController.view.alpha = 0;

    [UIView animateWithDuration:[self transitionDuration:transitionContext] animations:^{
        fromViewController.view.alpha = 0;
        toViewController.view.alpha = 1;
        fromViewController.specialView = [toViewController detailSpecialViewFrame];
    } completion:^(BOOL finished) {
        [transitionContext completeTransition:![transitionContext transitionWasCancelled]];

    }];

}

Answer 1

调用layoutIfNeeded（而不是layoutSubviews）来强制布局传递。然后应该更新框架。