iOS 7自定义转场故障

Question

这个视频展示了我遇到的问题。 http://www.youtube.com/watch?v=C9od_2KZAbs 我正在尝试使用UIPanGestureRecognizer创建自定义推送交互式转换。我有一个交互式转换代理（使用UIPercentDrivenInteractiveTransition）和一个转换动画师。

以下是平移手势如何控制转换的方式：

- (void) panGestureRecognized:(UIPanGestureRecognizer *) gestureRecogznier {

    CGPoint translation = [gestureRecogznier translationInView:gestureRecogznier.view];

    if (gestureRecogznier.state == UIGestureRecognizerStateBegan) {

        self.interactiveTransitionAnimator = [[UIPercentDrivenInteractiveTransition alloc] init];

        EVDetailViewController *detailViewController = [self.storyboard instantiateViewControllerWithIdentifier:@"EVDetailViewController"];
        [self.navigationController pushViewController:detailViewController animated:YES];
    }
    else if (gestureRecogznier.state == UIGestureRecognizerStateChanged) {

        CGFloat d = (translation.x / CGRectGetWidth(self.view.bounds)) * -1;
        [self.interactiveTransitionAnimator updateInteractiveTransition:d];
    }
    else if (gestureRecogznier.state == UIGestureRecognizerStateEnded) {

        if ([gestureRecogznier velocityInView:self.view].x < 0) {
            [self.interactiveTransitionAnimator finishInteractiveTransition];
        } else {
            [self.interactiveTransitionAnimator cancelInteractiveTransition];
        }

        self.interactiveTransitionAnimator = nil;
    }
}

UINavigationControllerDelegate 处理两个转场代理对象的提供，当调用 pushViewController: 时触发。

转场动画器具有非常简单的动画：

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

    UIViewController* toViewController = [transitionContext viewControllerForKey:UITransitionContextToViewControllerKey];
    [[transitionContext containerView] addSubview:toViewController.view];

    CGRect finalToVCFrame = [transitionContext finalFrameForViewController:toViewController];

    if (self.operation == UINavigationControllerOperationPush) {

        // set offscreen to the right
        toViewController.view.frame = CGRectMake(320.0f, 0.0f, 320.0f, 568.0f);

        [UIView animateWithDuration:[self transitionDuration:transitionContext] delay:0.0f options:0 animations:^{

            toViewController.view.frame = finalToVCFrame;

        } completion:^(BOOL finished) {

            // *** When this is called, the glitch occurs
            [transitionContext completeTransition:YES];
        }];
    }
}

在视频中，平移手势在大约60%的位置结束，这触发了finishInteractiveTransition调用。一切顺利，直到UIView基于块的动画中的完成块调用completeTransition:。当调用此方法时，toViewController不必要地重新播放推送动画的最后部分。在视频中，红色视图是窗口。动画持续时间为3秒。

我无法弄清楚为什么会发生这种情况。看起来在手势结束和调用completeTransition:之间的动画发生了两次。有什么想法吗？

- Erik Villegas

Answer 1

iOS 7.1起，我可以在模拟器中重现此问题，但在实际设备上却不行。无论如何，似乎有一个解决方法：

self.interactiveTransitionAnimator.completionSpeed = 0.999;

这个问题有一个雷达：rdar://14675246

- secondcitysaint

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哦，我的天啊，你刚刚为我节省了很多时间！ - Rudolf Adamkovič

我简直无法相信由于苹果的一个烂漫错误，我花了这么长时间才发现这个。谢谢。 - andrei

Answer 2

如果你在调用finishInteractiveTransition后立即调用[transitionContext completeTransition:YES];会发生什么呢？

else if (gestureRecogznier.state == UIGestureRecognizerStateEnded) {

    if ([gestureRecogznier velocityInView:self.view].x < 0) {
        [self.interactiveTransitionAnimator finishInteractiveTransition];
        [transitionContext completeTransition:YES];
    } else {
        [self.interactiveTransitionAnimator cancelInteractiveTransition];
    }

    self.interactiveTransitionAnimator = nil;
}

- ryan cumley

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似乎必须在finishInteractiveTransition完成剩余动画后调用completeTransition。所以我做的是延迟后执行performSelector，这样就解决了问题。然而，使用这种方法会导致返回按钮的箭头短暂闪烁。 - Erik Villegas

Answer 3

或者，正如matt在这里所观察到的那样，你也可以推迟completeTransition的执行，或者自己驱动自定义交互控制器：

I've seen something similar. I have two possible workarounds. One is to use delayed performance in the animation completion handler:

   } completion:^(BOOL finished) {
            double delayInSeconds = 0.1;
            dispatch_time_t popTime = 
                 dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
            dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
                BOOL cancelled = [transitionContext transitionWasCancelled];
                [transitionContext completeTransition:!cancelled];
            });
           self.interacting = NO;
    }];

The other possibility is: don't use percent-drive animation! I've never had a problem like this when driving the interactive custom animation myself manually.

- Rob

Answer 4

我有一个在Github上运行无误的示例（链接）。如果您有进一步的问题，请告诉我。

- just.jimmy

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缺少 project.pbxproj 文件。 - Ari Braginsky