自定义缩放过渡不适用于模态演示

Question

我正在尝试创建 缩放过渡。当它用于“推动”时，我让它工作得很好。现在我需要为模态转换工作，当然不能只是 2 分钟的修复。

转换是从一个NavigationController 到另一个。我还是不明白当ViewController键指向NavigationControllers时，它们应该指向实际的ViewControllers？

这正是我想要的，但所提供的控制器上的 viewWillAppear 永远不会被调用，NavigationBar 也不会出现。

请帮助我。我会给出我必须得到答案的每一分！

这里是动画方法：

-(void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext
{
    UINavigationController *fromNav = (id)[transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    UINavigationController *toNav = (id)[transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];

    UIViewController<SWZoomTransitionDelegate> *fromVC= (UIViewController<SWZoomTransitionDelegate> *)fromNav.topViewController;
    UIViewController <SWZoomTransitionDelegate> *toVC =  (UIViewController<SWZoomTransitionDelegate> *)toNav.topViewController;

    UIView * containerView = [transitionContext containerView];
    UIView * fromView = [fromVC view];
    UIView * toView = [toVC view];

    [containerView addSubview:toView];

    UIView * zoomFromView = [fromVC viewForZoomTransition];
    UIView * zoomToView = [toVC viewForZoomTransition];

    UIImageView * animatingImageView = [self initialZoomSnapshotFromView:zoomFromView
                                                         destinationView:zoomToView];

    if ([fromVC respondsToSelector:@selector(initialZoomViewSnapshotFromProposedSnapshot:)])
    {
        animatingImageView = [fromVC initialZoomViewSnapshotFromProposedSnapshot:animatingImageView];
    }

    animatingImageView.frame = [zoomFromView.superview convertRect:zoomFromView.frame
                                                            toView:containerView];

    fromView.alpha = 1;
    toView.alpha = 0;
    zoomFromView.alpha = 0;
    zoomToView.alpha = 0;
    [containerView addSubview:animatingImageView];

    ZoomAnimationBlock animationBlock = nil;
    if ([fromVC respondsToSelector:@selector(animationBlockForZoomTransition)])
    {
        animationBlock = [fromVC animationBlockForZoomTransition];
    }

    [UIView animateKeyframesWithDuration:self.transitionDuration
                                   delay:0
                                 options:self.transitionAnimationOption
                              animations:^{
                                  animatingImageView.frame = [zoomToView.superview convertRect:zoomToView.frame toView:containerView];
                                  fromView.alpha = 0;
                                  toView.alpha = 1;

                                  if (animationBlock)
                                  {
                                      animationBlock(animatingImageView,zoomFromView,zoomToView);
                                  }
                              } completion:^(BOOL finished) {
                                  if ([transitionContext transitionWasCancelled]) {
                                      [toView removeFromSuperview];
                                      [transitionContext completeTransition:NO];
                                      zoomFromView.alpha = 1;
                                  } else {
                                      [fromView removeFromSuperview];
                                      [transitionContext completeTransition:YES];
                                      zoomToView.alpha = 1;
                                  }
                                  [animatingImageView removeFromSuperview];
                              }];
}

Answer 1

我在另一个项目中遇到了类似的问题。根据the WWDC session，调用viewWillAppear: 绝对是预期行为：

所以当一个交互式过渡开始时，UIKit 背后的机制实际上会调用视图，视图会消失，会显示视图控制器，所有你通常习惯的东西控制您的应用程序在屏幕出现和显示时发生的事情。

在我的例子中，问题是动画对象在过渡期间被释放。我是这样设置动画师的：

- (id<UIViewControllerAnimatedTransitioning>)animationControllerForPresentedController:(UIViewController *)presented
                                                                  presentingController:(UIViewController *)presenting
                                                                        sourceController:(UIViewController *)source {

    AGBAnimator *animator = [AGBAnimator new];
    return animator;
}

此对象超出范围并在动画期间被释放。通过创建strong属性并在从该方法返回之前为其分配animator，问题得到解决并成功调用viewWillAppear:等。