iOS7自定义过渡调用了两次

Question

我想为 UITabBarController 的选项卡之间的过渡设置动画。 .出于某种原因，此方法来自 UIViewControllerAnimatedTransitioning协议(protocol)被调用两次:

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

堆栈跟踪:

紧接着:

还有 - (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

对于第一印象，我相信 - (void)animationEnded:(BOOL)transitionCompleted被调用两次，因为你调用了 [transitionContext completeTransition:YES] ，它基于苹果文档:

Call this method after your animations have completed to notify the system that the transition animation is done. The default implementation of this method calls the animator’s animationEnded: method to give it a chance to perform any last minute cleanup.

如果 UIViewControllerAnimatedTransitioning被调用两次然后就可以了。

进一步分析为什么UIViewControllerAnimatedTransitioning被叫了两次我很高兴看到你的animationControllerForPresentedController和 animationControllerForDismissedController执行。