ios - 如何将自动布局与容器转换一起使用？

Question

如何通过 UIViewController 容器转换方法使用自动布局:

-(void)transitionFromViewController:(UIViewController *)fromViewController
                   toViewController:(UIViewController *)toViewController 
                           duration:(NSTimeInterval)duration
                            options:(UIViewAnimationOptions)options
                         animations:(void (^)(void))animations
                         completion:(void (^)(BOOL finished))completion;

传统上，使用 Springs/Struts，您设置初始帧(就在调用此方法之前)并在传递给该方法的动画 block 中设置最终帧。

该方法负责将 View 添加到 View 层次结构并为您运行动画。

问题是我们不能在同一位置(方法调用之前)添加初始约束，因为 View 尚未添加到 View 层次结构中。

关于如何将此方法与自动布局一起使用，我有什么想法吗？

下面是使用 Springs/Struts(框架)执行此操作的示例(感谢 cocoanetics) http://www.cocoanetics.com/2012/04/containing-viewcontrollers

- (void)transitionFromViewController:(UIViewController *)fromViewController toViewController:(UIViewController *)toViewController
{

    // XXX We can't add constraints here because the view is not yet in the view hierarchy
    // animation setup 
    toViewController.view.frame = _containerView.bounds;
    toViewController.view.autoresizingMask = _containerView.autoresizingMask;

    // notify
    [fromViewController willMoveToParentViewController:nil];
    [self addChildViewController:toViewController];

    // transition
    [self transitionFromViewController:fromViewController
                      toViewController:toViewController
                              duration:1.0
                               options:UIViewAnimationOptionTransitionCurlDown
                            animations:^{
                            }
                            completion:^(BOOL finished) {
                                [toViewController didMoveToParentViewController:self];
                                [fromViewController removeFromParentViewController];
                            }];
}

Answer 1

开始思考实用方法transitionFromViewController:toViewController:duration:options:animations:completion 无法与 Auto Layout 一起干净地工作。

现在我已经用直接调用每个“较低级别”的包含方法代替了我对这种方法的使用。它的代码有点多，但似乎提供了更大的控制权。

看起来像这样:

- (void) performTransitionFromViewController:(UIViewController*)fromVc toViewController:(UIViewController*)toVc {

    [fromVc willMoveToParentViewController:nil];
    [self addChildViewController:toVc];

    UIView *toView = toVc.view;
    UIView *fromView = fromVc.view;

    [self.containerView addSubview:toView];

    // TODO: set initial layout constraints here

    [self.containerView layoutIfNeeded];

    [UIView animateWithDuration:.25
                          delay:0
                        options:0
                     animations:^{

                         // TODO: set final layout constraints here

                         [self.containerView layoutIfNeeded];

                     } completion:^(BOOL finished) {
                         [toVc didMoveToParentViewController:self];
                         [fromView removeFromSuperview];
                         [fromVc removeFromParentViewController];
                     }];
}