iOS7自定义转换调用两次

Question

我想为UITabBarController的标签之间的转换设置动画。出于某种原因，UIViewControllerAnimatedTransitioning协议中的此方法被调用两次：

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext

堆栈跟踪： 紧接着： 此外，- (void)animationEnded:(BOOL)transitionCompleted方法被调用两次。

我不知道为什么。

这是代码：

- (void)animateTransition:(id<UIViewControllerContextTransitioning>)transitionContext {

    UIView *containerView = [transitionContext containerView];

    UIViewController *fromVC = [transitionContext viewControllerForKey:UITransitionContextFromViewControllerKey];
    UIViewController *toVC = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];

    [toVC.view setTransform:CGAffineTransformMakeTranslation(320, 0)];

    [containerView addSubview:toVC.view];

    [UIView animateWithDuration:0.5 animations:^{
        [toVC.view setTransform:CGAffineTransformIdentity];
        [fromVC.view setTransform:CGAffineTransformMakeTranslation(-320, 0)];
    } completion:^(BOOL finished) {
        [fromVC.view setTransform:CGAffineTransformIdentity];
        [toVC.view setTransform:CGAffineTransformIdentity];
        [transitionContext completeTransition:YES];
    }];

}

Answer 1

对于第一次展示，我认为- (void)animationEnded:(BOOL)transitionCompleted会被调用两次，因为您调用基于Apple文档的[transitionContext completeTransition:YES]：

  

在动画完成后调用此方法以通知系统已完成过渡动画。此方法的默认实现调用动画师的 animationEnded ：方法，使其有机会执行最后一分钟的清理。

如果UIViewControllerAnimatedTransitioning被调用两次，那么就去吧。

为了进一步分析为什么UIViewControllerAnimatedTransitioning被调用两次，我很高兴看到您的animationControllerForPresentedController和animationControllerForDismissedController实施。